M. K. Korovin and A. B. Travin

Petrographic Study of Coals from the Prienisei-Abakan Trough of the Minusinsk Coal Basin

INTRODUCTION

The present work was carried out within the system of the Scientific-Research Coal Institute of Kuzbassugol, in the geological section of the institute (Tomsk), in 1932–1933. The formulation of the topic and its execution were connected with the question of obtaining an independent coke base in the Khakass-Minusinsk region and corresponded to the problem of ferrous metallurgy in this region according to the first versions of the second five-year plan. The subsequent removal of the problem from the second five-year plan caused a decrease in the urgency of the topic, and at the same time a delay in the publication of the present work.

The renewed posing of the problem of ferrous metallurgy in Khakassia in the third five-year plan restores the urgency of the coke problem, as well as of the present work, which for the first time in our literature illuminates the question of the coking of Minusinsk coals from the petrographic point of view.

The work was conducted with the aim of analyzing the petrographic composition of the Minusinsk coals with respect to their caking ability and thereby bringing possible clarity to the view, established in our literature, that Minusinsk coals are hopeless with respect to coking.

In doing so, the authors set themselves the task, in a small investigation, of illuminating the petrographic composition of the coals both of the Chernogorsk deposit and of other coal deposits of the basin in which workings existed that permitted the taking of a special petrographic sample. Such were (Fig. 1) the Izykh deposit and the deposit of the so-called Kalyagin exploration (Narylkovo), located in the southeastern part of the Prienisei-Abakan trough. The extensive material thus obtained necessarily had to be studied unevenly: of the four seams of the Chernogorsk deposit, only the Gigant seam was subjected to microscopic analysis, since the microscopy of the other seams had already found reflection in our literature (the works of Zalessky, Ergolskaya, and Elovskaya). It must also be noted that the petrographic analysis of coal from seven seams of the Prienisei-Abakan trough was carried out on the basis of the study of samples from only one point for each seam.

Of course, all the conclusions of the present work, carried out under the above-mentioned conditions, cannot be regarded as final, requiring additional and more detailed investigations. However, the fairly great constancy by which, in general, the petrographic and chemical composition and the physical properties of Minusinsk coals from different seams are characterized gives grounds for regarding the results of the present work as very probable.

The essentially practical task set by the authors for the present work was also the reason for a somewhat unusual method of petrographic investigation. Its essence is as follows. The overwhelming majority of modern petrographic works on coal analyze this fossil, differentiating it into coal ingredients and recording in it various formed organic formations and mine—

SCHEMATIC MAP

OF THE PRIENISEI–ABAKAN COAL DISTRICT

Scale

[map]

Legend:

• Coal-bearing deposits.
• Lower Carboniferous and Upper Devonian.
• Worked and closed mines.

Fig. 1

mineral impurities, present in various combinations that determine the structure and texture of the coal. This makes it possible to reveal the primary nature of the parent substance of the coal, explains certain features of the chemical composition and the physical and technical properties of the coal, and clarifies the conditions under which plant material accumulated and, in general, the genesis of the coal. But when attempting to make use of the results obtained in the investigation, we often encounter great difficulties here in practically separating the microscopically recorded ingredients, which are often distributed extremely unevenly throughout the entire mass of the coal. A simple way out of this difficulty was outlined in the German school of petrographers, which reduced the whole diversity of coal ingredients to three basic types: bright, dull, and fibrous coals, easily distinguished also macroscopically. The authors of the present work have followed the same path in general. We distinguish the simple ingredients fusite and vitrite, which are readily differentiated macroscopically, and divide the entire remaining mass of coal substance, complex in composition, into two large groups of coals—bright and dull—subdividing them, moreover, internally according to their macroscopically distinguishable degree of luster¹. At the same time, we regard the individual elements of the internal subdivision of bright and dull coals as complex petrographic complexes, usually representing combinations of various and also compositionally complex bright (for example, clarite) and dull (durite) coals. We therefore assess them as higher systematic units, qualifying them by the name of genera (I, II, III genera of bright coals; I, II, III, and IV genera of dull coals).

The material analyzed by us is far too insufficient for us to see, in the petrographic-analysis method indicated above, any experience in the petrographic classification of coals. But it is interesting that some of the genera of coals we have distinguished, as will be seen below, persist in various seams, while retaining their petrographic and physical properties, and are indeed petrographic types. At the same time, the simplicity of the practical distinction of coal genera in all cases leaves no room for doubt.

The present study was carried out at the Department of Historical Geology and the Geology of Caustobioliths of the Tomsk Industrial Institute (TII), using its rooms and laboratories.

The entire investigation was conducted jointly by both authors under the direction of M. K. Korovin. But in the experimental part the main work was carried out by A. B. Travin (now a student of TII); in the synthesis of the material obtained and in its presentation, the principal role belongs to M. K. Korovin.

CHERNOGORSK DEPOSIT

I. The Gigant Seam

1. Macroscopic description.

The place where the sample from the Gigant seam was taken was shaft No. 9, driven by the Mine Administration of the Chernogorsk mine in the autumn of 1931. The shaft exposed the seam at the 21 m level and, having been carried to the floor of the seam at a depth of 28 m, was stopped.

Here the seam has a useful thickness of 4.6 m and consists of three benches separated by two interlayers of barren rock.

It was not possible to strip the upper bench, separated from the two lower ones by an interlayer of gray sandy argillite 1.15 m thick, because during the stripping a timber set was lowered in the shaft down to the roof of the second (from top to bottom) bench.

For technical reasons it was not possible to carry out correct sampling

coal samples from the second bench as well. Here, instead of cutting out a vertical column of coal through the entire thickness of the bench and thereby obtaining a complete representation of it, it was necessary to divide all the coal composing this bench into several layers with more or less identical macroscopic characteristics, and then to take several hand specimens of coal from each such layer.

It is clear that the thickness represented by the hand specimens proved to be considerably less than the true thickness of this bench, amounting to only about half of it.

The proper sampling of the specimen was achieved only in the third bench (with a thickness of 1.05 m), where technical conditions made it possible to collect the hand specimens so that, in sequence, they together formed a column characterizing the entire thickness of the given bench (Fig. 2).

It is also necessary to note the shallow depth of occurrence of the seam at the place where it was sampled (21–28 m), while the depth of the weathering zone for the Minusinsk coal district is no less than 50–70 m.

The macroscopic description of the seam given below was made from individual coal hand specimens, with a simultaneous calculation (by the Rozival method) of the macroscopically distinguishable coal ingredients.

In the course of such study, the entire seam could be divided into two principal groups of coal—the group of bright coals and the group of dull coals, with the further separation from them of especially fibrous and vitrain coals that were amenable to macroscopic accounting. In addition to this subdivision, it was possible to divide each of the distinguished groups, according to decreasing degree of luster and other features, into several kinds of coal.

Schematic section of the lower bench of the “Gigant” seam of the CHERNOGORSK mine.

Legend

• Bright, shiny coal
• Dull coal
• Barren rock

Scale: 1 cm = 8 centimeters

Fig. 2.

In the composition of the seam, both groups take almost equal part and constitute its principal mass. Thus, the content of bright coals reaches 44%, that of dull coals—48%, and of both together—92%. Macroscopically distinguished vitrite accounts for 4%, while fibrous coal (fusite) accounts for only 1%. The remaining 3% falls to barren rocks, which participate in the composition of the seam usually in the form of very thin interbeds (1–4 mm) and consist of sandy-clayey, clayey, and ferruginous formations. The thickness of these interbeds sometimes rises to 30 mm, and sometimes falls to 0.5 mm. Such insignificant interbeds of barren rock were difficult to separate when taking coal samples, which therefore proved to be somewhat contaminated. This circumstance, of course, adversely affected the results of the analyses given below, lowering also the caking capacity of the coal.

Let us note here also that mineral material in this seam is often observed along the bedding planes in the form of the thinnest dull clayey and carbonaceous-clayey films, contaminating the coal still further.

The description of the coal composing the seam is given below according to the principal groups and varieties of coal.

Bright coals.

This group includes three varieties of bright coal, characterized by different macroscopic features, such as: different luster, fracture, degree of mineralization, hardness, and, finally, texture.

In order of decreasing luster and increasing content of mineral impurities in them, we have distinguished I, II, and III varieties of bright coal.

Bright coal of variety I. To variety I of this group was assigned coal possessing a comparatively strong glassy luster approaching resinous, a streaky (slightly relief) texture, and a more or less even and coarse fracture. The coal is fairly hard, weakly broken by cleavage cracks, and has a tendency to split readily along the bedding, sometimes into thin plates (for example, samples from the lower part of the 3rd band). The banding in this coal is sharp and is expressed in the alternation of weakly lustrous bands of the principal clarito-durite mass, strongly lustrous bands of vitrite, and the thinnest dull bands of durite. Coal of this variety has been named by us clarito-durite coal. It is sometimes strongly enriched with calcite, which fills small cracks cutting the coal in different directions.

Bright coal of variety II. Like the first, this coal is distinguished by a streaky texture and has an almost resinous luster, but a weaker one. The latter is explained both by the lesser luster of the principal coal mass and by the greater content of dull durite bands, which, although not absolutely dull, nevertheless reduce the luster of the general mass of the coal. This gives grounds for naming coal of this variety durito-clarite, i.e., coal standing closer to durite. In comparison with the first variety, here there is also observed a certain increase in the content of fusite and a larger number of cleavage cracks. The general mass of this coal therefore appears less homogeneous, more fissured, and possesses a fine uneven fracture.

Bright coal of variety III is characterized by a banded texture. It consists of a principal, weakly lustrous durito-clarite mass and alternating with it bands and lenses of fusite and vitrite, mineral and mineralized interbeds. The latter two include interbeds either of barren rocks or of coal occurring in fine mixture with mineral mass, as if cementing the coal.

The main mass of this coal, in luster and in the number of shrinkage cracks, differs little from durito-clarite coal of the second type and is distinguished from it chiefly by the fact that it contains more finely disseminated fusite and mineral interbeds, as well as small mineral inclusions in the form of oolitic grains of brown iron ore. This coal may therefore be called mineralized durito-clarite coal.

Thus, the bright coals (Group I), on the basis of macroscopic features, show from type I to type III a successive decrease in luster and, at the same time, a successive increase in the amount of mineral inclusions.

Dull coals.

This group consists of four types, differing from one another in luster, fracture, texture, strength and degree of mineralization, as well as in color.

Dull coal of type I. This coal has a very weak, heterogeneous luster, an irregular fracture, and a banded structure; it consists of alternating almost dull bands of durite, weakly lustrous bands of durito-clarite, strongly lustrous vitrite, and sooty bands of fusite. It differs from the coals of the preceding group by its considerably greater strength, being little broken by weakly expressed shrinkage cracks.

Interbeds and lenses of vitrite and fusite are usually so thin that macroscopically it was possible to count only very few of them. The bands of clarito-durite coal are also of small thickness. And only the dull bands of durite, which make up the main mass of the coal, are characterized by a rather considerable thickness. Coal of this type may therefore be called banded durite coal.

Dull coal of type II occupies a somewhat special position in this group, differing by a higher content of vitrite and mineral material. The latter is expressed macroscopically not as separate interbeds and lenses of barren rocks, but as a fine intermixing of mineral and coal matter, as if by impregnation of the coal with mineral substance. The mineralized coal is usually interbedded with fairly numerous, predominantly thin interbeds and lenses of vitrite. This coal then has a granular texture and a very weak heterogeneous luster, which are caused by the inclusion, in the general dull mass, of very small lustrous grains barely noticeable to the eye—probably the tiniest lenses and areas of vitrite.

The mineralized coal has a brownish dark-gray color, is extremely strong, bears absolutely no fissuring, and contains many oolitic grains of brown iron ore, which sometimes group into continuous areas and even whole interbeds. The fracture of the coal is coarse and uneven. We distinguish this coal under the name of mineralized durite coal.

Dull coal of type III has a very weak dull-greasy luster, is distinguished by a massive structure, consists essentially of durite, and is very strong and dense. Its color is dark gray. The fracture is coarse, uneven, and flat-conchoidal. Shrinkage cracks are absent. Along the bedding planes of the coal, rare and very small films of hard fusite are sometimes observed. Vitrite is macroscopically imperceptible. All this gives grounds to call this coal massive durite coal.

Dull coal of type IV. The coal is strong, almost dull; it has an uneven fracture, cleaves easily along the bedding, and contains very many lenses of hard and soft fusite, especially the latter. Shrinkage cracks in the coal are almost not manifested, with the exception of faintly indicated ones perpendicular to the bedding.

The high content of fusite in this coal is especially characteristic along the bedding planes, where large areas can be seen entirely covered with films of hard and more often soft fusite. Fusite causes heterogeneity in the composition of the coal, unevenness of its fracture, and a tendency to split along the bedding. Coal of this kind may be called durite–fusite coal.

It is not without interest to compare the coals of groups I and II. It turns out that the dull durite coals of group II are characterized by: 1) considerably greater strength than the coals of group I, 2) a weak manifestation of fracturing, and 3) a considerably higher content of fusite throughout the group as a whole.

From the composition of the lustrous and dull coals described above, we distinguish macroscopically vitrite and fibrous coal, and mineral inclusions. They are characterized as follows.

Vitrite coal is characterized by a strong glassy-resinous luster, a flat-conchoidal fracture, and the greatest degree of fracturing of all the other coal components. This coal enters, in greater or lesser quantity, into the composition of all the varieties of lustrous and dull coals distinguished in the seam. It is usually observed in the form of thin lenses, more rarely in the form of broader interbeds, and also as fine films along the bedding planes. The thickness of the lenses and interbeds is almost always less than 2 mm and only in rare cases reaches 3–4 mm.

The numerous joints of separation characteristic of vitrite coal usually run in it in one direction, more rarely in two directions at small angles to one another, and in both cases more or less perpendicular to the bedding. The presence of such fracturing in the coal causes a more or less uneven fracture, which is usually accompanied also by a flat-conchoidal fracture.

Vitrite interbeds are also accompanied by a slight dull tarnish, clearly revealed along the planes of fracturing.

Along the bedding planes of the coal, vitrite is observed as small lenses with slight convexity in the center and rounded contours at the edges. These lenses can often be observed in direct connection with thin films of fusite and, more rarely, with still thinner dark-gray films, probably of one of the dull varieties of coal. Not infrequently the vitrite lenses are grouped together and in these cases sometimes occupy considerable areas on planes parallel to the bedding.

Fibrous coal (fusite) is developed in the seam most often in the form of very small lenses, whose thickness is usually less than 0.5 mm, rarely reaching 1.5–2 mm. The small thickness of these lenses does not allow many of them to be recorded macroscopically, although they are readily observed in large numbers along the bedding planes in the form of films.

Fusite is present in greater or lesser quantity in all varieties of coal, but it is distributed among them very unevenly, strongly enriching the IV varieties of dull coal and the III variety of lustrous coal, and least of all the II variety of lustrous coal and the III of dull coal.

Two types of fusite are distinguished: 1) soft fusite—sooty, strongly staining the hands, black, with a strong silky luster; macroscopically it is clearly visible. 2) Hard fusite—stains the hands very weakly; its color ranges from gray to brownish (in the latter case, probably mineralized); it is almost dull, with a slightly expressed weak silky luster. Lenses of such fusite are often difficult to distinguish in the seam, especially in the dull varieties.

Films of fusite observed along the bedding planes usually have rectilinear boundaries and a fairly well expressed fibrous texture.

In addition to the already mentioned primary mineral formations in the form of films and interlayers, or finely dispersed in the coal mass, the seam also contains mineral inclusions of secondary origin, such as: oolitic grains of brown iron ore, pyrite, and calcite.

Oolitic grains of brown iron ore are observed in the seam in fairly large quantities, with average cross-sectional dimensions of 1–1.5 mm.

Pyrite is much less widespread; it is usually observed in the form of small oval films situated along joint cracks, more often in bright coals and more rarely in dull ones. This distribution of pyrite is probably explained by the greater fissuring of certain bright coals. Individual oval pyrite films sometimes merge and then form large films with irregular outlines.

Calcite, like pyrite, is observed along joint cracks in the form of thin films with uneven outlines. It is distributed chiefly at the very floor of the seam.

The distribution of bright and dull coals, vitrite, fusite, and mineral inclusions over the two studied benches of the seam may be characterized as follows (Fig. 3).

Bright coals (clarito-durites and durito-clarites) are distributed rather uniformly through the benches in their total amount, but very unevenly by individual types. The total content of bright coals varies only slightly in the two benches: from 49% in the second (upper) bench to 40% in the third. However, the content of the individual types by bench is extremely variable and subject to abrupt jumps. Thus, type II bright coal, which composes 41% of the second bench, composes only 1% of the third bench. Almost the same is observed for type I, which in the third bench, together with coal strongly enriched in calcite, gives 28%, and in the second only 8%. Type III bright coal is completely absent in the second bench, but constitutes a substantial percentage (11%) in the third bench. It should also be noted that bright coals of type I and partly type II form a considerable interlayer, 17.5 cm thick, at the very floor of the seam. This interlayer also includes a thin interbed of type I bright coal (3.6 cm), strongly enriched in calcite.

Dull (durite) coals are distributed among the benches in exactly the same way, rather uniformly, composing 45% of the second bench and 49% of the third bench. However, the distribution of the individual types of these coals by bench also fluctuates sharply. Thus, for example, whereas the second bench is characterized by a comparatively high content of dull coal of type II (11%) and a low content of types III and IV (5% each), the third bench has no type II at all, very little type III (2.4%), and, conversely, contains much dull coal of type IV (12%). In both the second and the third benches, the main mass of dull coals consists of type I (respectively, by benches, 24% and 35%). Vitrite enriches the second bench somewhat more, but in general its content by bench varies little.

Fibrous coal (fusite) is distributed mainly in the third bench.

Mineral formations in the form of interlayers of barren rocks are developed chiefly in the third (lower) bench, where their content reaches 5%. They are distributed here more or less uniformly, usually having very small thicknesses. In the composition of this bench, interlayers of mineralized coal and small oolitic grains of brown iron ore, usually closely associated with the former, also take a considerable part. As those,

Fig. 3

Legend

• Vitrinite
• Bright coal, type I.
• Bright coal, type II.
• Bright coal, type III.
• Dull coal, type I.
• Dull coal, type II.
• Dull coal, type III.
• Dull coal, type IV.
• Fusite
• Carbonaceous argillite
• Argillite

Scale:
1 centimeter = 2 centimeters

Labels on columns: Bed 2, Bed 3.

both the one and the other are developed unevenly throughout the entire thickness of the bench, substantially enriching its middle part.

The content of barren-rock interbeds in the second bench is only 1%. As for interbeds of mineralized coal and oolitic grains of brown iron ore, their content in the second bench is approximately the same as in the third. They are observed in close association with one another and to a considerable degree enrich the upper part of the bench, 8.5 cm thick.

Tectonic disturbances at the sampling point of the seam are very weakly expressed. If the cleavage cracks are disregarded, only slickenside surfaces should be included here; these, however, are observed rarely and are indistinctly expressed.

The principal data on the macroscopic composition of the Gigant seam are summarized in Table No. 1.

2. Microscopic description.

The following microscopic description is given for the separate coal types, as was done above. In this classification of the petrographic ingredients of coal has been made by us according to the degree of preservation of the plant tissues that took part in the formation of the coals.

The general characteristics of the principal ingredients are as follows.

Fusite is preserved tissue with a clearly expressed cellular structure. The cell walls are usually light-yellow in color (fusitic cellulose of light-gray color is encountered rarely) and have varying thickness. The cell cavities, with rare exceptions, are free of organic matter, but are sometimes filled with calcite.

According to the diameter of the cells, fusitic cellulose occurs as small-, medium-, and large-celled (Figs. Nos. 4, 5, 6¹), and according to the thickness of the cell walls as thick-walled and thin-walled. It turns out that thick-walled and thin-walled fusite may be independent of whether it has a large-celled or small-celled structure. The difference in cell diameter and in the thickness of the cell walls, which is observed in a number of fusitic formations, may be explained by the fact that the latter (lenses and fragments of fusite) belonged either to different parts of one plant individual (bark tissue, wood proper, leaves, etc.), or to different species of plants. But this may also be a consequence of the alteration of the cell walls during coalification.

Fusite is developed in the coal of the Gigant seam predominantly in the form of small lenses and fragments (large lenses are encountered comparatively rarely) of small- and medium-celled, more rarely large-celled, structure.

In addition, a large number of fusitic formations with thin-walled cellulose is characteristic of the seam.

Xylite of the 1st type. Included here are remains of plant cellulose whose cells are almost entirely or partially filled with a light-yellow colloidal organic mass (the color of the latter is quite similar to the color of the cell walls). The percentage of filling of the cells varies from 10 to 90%. The grouping into one category of cellular areas whose percentage of filling varies within such broad limits was caused by the difficulty of technically taking into account all the diversity of transitions from less altered plant material to more altered material.

¹ The figures of microphotographs and microdrawings are placed at the end of the description of the coals of the Gigant seam.

Table No. 1

Macroscopic composition of the coal of the Gigant seam

Main coal groups	Coal varieties	Probable nature of the coal	II bench: pit No.	II bench: total coal thickness in individual pits, mm	II bench: sum, mm	II bench: % of bench thickness	III bench: pit No.	III bench: coal-variety thickness in individual pits, mm	III bench: sum, mm	III bench: % of bench thickness	Average % over the whole seam
Lustrous coals	1st variety	Clarite-durite coal	1 8	57,0 3,5	60,5	8,0	10 12 14 16 18 19 20 21	34,0 24,5 5,0 20,0 30,0 64,0 48,0 16,0	241,5	24,0	17,0
Lustrous coals	1st variety with fusain	Clarite-durite coal	—	—	—	—	—	36,0	36,0	4,0	2,0
Lustrous coals	2nd variety	Durite-clarite coal	3 4 5 8	62,2 124,5 105,0 26,0	317,7	41,0	11	12,0	12,0	1	19,0
Lustrous coals	3rd variety	Mineralized durite-clarite coal					10 13 15 16	35,0 9,0 50,0 19,0	113	11	60
Dull coals	1st variety	Banded durite coal	1 2 6 7	75,5 18,0 77,0 10,5	181,0	24,0	12 13 14 16 17 18	77,5 80,0 85,5 34,0 29,5 43,0	349,5	35	30
Dull coals	2nd variety	Mineralized durite coal	8	85,0	85,0	11,0	—	—	—	—	5,0
Dull coals	3rd variety	Massive durite coal	1	36,5	36,5	5,0	11 15 19	13,0 4,0 4,0	21,0	2	4,0
Dull coals	4th variety	Durite-fusite coal	7	38,0	38,0	5,0	11 14 15 17	43,0 27,0 4,0 50,5	124,5	12	9
Vitrite coal	Vitrite coal	Vitrite	1 2 3 4 5 6 7 8 9	1,0 7,7 3,5 6,0 7,5 3,2 0,5 8,2 waste rock	37,6	5,0	10 11 12 13 14 15 16 17 18 19 20 21	2,6 0,5 1,2 1,5 3,2 3,5 4,0 2,7 0,9 11,7 2,0 2,6	36	4,0	4

Principal groups of coals	Coal varieties	Probable nature of the coal	II bench: No. of pieces	II bench: total coal thickness in individual pieces, mm	II bench: Sum, mm	II bench: % of bench thickness	III bench: No. of pieces	III bench: Thickness of coal variety in individual pieces, mm	III bench: Sum, mm	III bench: % of bench thickness	Average %, over the whole seam
Fibrous coal	Fibrous coal	Fusite	5	1.7	3.9	0.5	11	1.0	12	2.0	1.0
Fibrous coal	Fibrous coal	Fusite	6	1.2	3.9	0.5	13	0.5	12	2.0	1.0
Fibrous coal	Fibrous coal	Fusite	7	1.0	3.9	0.5	14	1.0	12	2.0	1.0
Fibrous coal	Fibrous coal	Fusite			3.9	0.5	15	4.3	12	2.0	1.0
Fibrous coal	Fibrous coal	Fusite			3.9	0.5	16	1.5	12	2.0	1.0
Fibrous coal	Fibrous coal	Fusite			3.9	0.5	17	2.0	12	2.0	1.0
Fibrous coal	Fibrous coal	Fusite			3.9	0.5	18	1.3	12	2.0	1.0
Fibrous coal	Fibrous coal	Fusite			3.9	0.5	19	0.7	12	2.0	1.0
Barren rock	Barren rock	—	3	3.5	6.5	1.0	10	3.0	54.7	5	3
Barren rock	Barren rock	—	5	3.0	6.5	1.0	12	29.2	54.7	5	3
Barren rock	Barren rock	—			6.5	1.0	13	16.0	54.7	5	3
Barren rock	Barren rock	—			6.5	1.0	15	4.0	54.7	5	3
Barren rock	Barren rock	—			6.5	1.0	16	0.7	54.7	5	3
Barren rock	Barren rock	—			6.5	1.0	18	1.0	54.7	5	3
Barren rock	Barren rock	—			6.5	1.0	20	0.3	54.7	5	3
Barren rock	Barren rock	—			6.5	1.0	21	0.4	54.7	5	3
					766				994

Xylite of type II represents remnants of plant tissue, in most cases wholly filled with a colloidal organic mass. Their color is more often light grayish-yellowish. Very rarely do these formations differ by an intensely expressed yellow coloration. The cellular structure in these formations disappears almost completely, and only the ragged outlines along their edges make it possible to assign such forms to fragments of plant tissue. The percentage to which the cells are filled by colloidal mass here ranges from 90% to 100%, the latter being observed more often.

Xylite of types I and II in the coal of the Gigant seam occurs in the form of interlayers, lenses, and fragments, sometimes more and sometimes less numerous, depending on the variety of coal in which they are contained. The thickness of both usually ranges within 0.03–0.10 mm. The xylitic tissue, like the fusitic tissue, is observed to have a coarse-, medium-, and fine-cellular structure.

In the overall content of xylite in the seam (Table 2), xylite of type I decidedly predominates.

Vitrite in the Gigant seam has all the features characteristic of it. It is observed in the form of lenses and interlayers predominantly 0.07–0.15 mm thick; it is distinguished by a light-gray color and is usually more or less fissured. In the composition of the studied sample of the Gigant seam, vitrite plays a subordinate role, macroscopically making up only 4% of its thickness. The microscopic content of vitrite is shown in Table 2. In the different varieties of coal it most often ranges from 2% to 5%.

Clarite, distinguished as a macroscopic ingredient in the sense of M. Stopes, under the microscope consists of a principal structureless light-gray mass and various shaped formations embedded in it. The principal structureless mass is, in external appearance, very similar to vitrite, but differs from it by the absence of fissuring. Since clarite plays a substantial role in the Minusinsk coals and in general belongs among the caking ingredients of coal, we shall dwell on its description in greater detail.

The formed elements of clarite must include the thin cuticle threads characteristic of it. They have a yellowish-brown color, often a considerable length, and are usually arranged along the bedding and more or less parallel to one another. More rarely they cut across the bedding in the form of irregular zigzag lines, their arrangement here too being more or less mutually parallel. Sometimes the cuticles are observed tightly compressed, as though entangled with one another. In addition to the thin brownish cuticles, larger ones (from 0.003 to 0.016 mm) of lilac-gray color are also often encountered here. Their edges are smooth and even on one side, toothed and uneven on the other (Fig. 20).

Sometimes the cuticles in clarite outline cellular areas on one side, more rarely on two sides. Preserved cuticles in the form of long threads of uniform thickness occur in clarite comparatively rarely. Usually they are strongly destroyed and are represented in it as numerous small fibrous fragments of yellowish-brown color.

After cuticles, the most widespread formed constituents in clarite are small lilac-gray fragments, more often of indeterminate origin. At higher magnifications it was nevertheless possible to establish that some of these formations are very small spores of lilac-gray color with toothed margins and a narrow cavity in the middle (see the drawing, Fig. 24). Formations identical to them in color, size, and partly in form are observed in the coals of the Serebrennikov seam of the Leninsk deposit, where they make up a very large percentage in the structural part of durite.

As is known, Minusinsk coals are close to the Leninsk coals in their high bituminousness, in connection with which they have a high content of volatile substances and a good yield of primary tar. It may be thought that the structural formations indicated above partly serve as the petrographic expression of the bituminousness of our coals.

Among the formed structures in the composition of clarite there are also small fragments of fusite and xylite tissue. In their microscopic features they are completely identical to the larger inclusions of fusite and xylite already described above.

Also deserving attention are lilac-gray inclusions, close to algae, generally few in number (in the entire seam sample they amount to no more than 1%). They sometimes have a cellular structure and are arranged along the bedding in the form of lenses or, more often, elongated formations rounded at the ends, not infrequently with a cavity in the middle (Figs. 9 and 10).

After etching with a mixture of chromic and sulfuric acids these formations reveal their structure more distinctly and prove to be accumulations of densely packed oval and cylindrical, irregularly curved bodies. Most of the bodies are solid and have no structure; a smaller portion of them, perhaps better preserved, reveals within itself an oval cavity (Fig. 11). These accumulations have been recorded by us as possible algae.

Of interest, in addition, are small inclusions of detrital appearance, having an irregular form, usually angular, sometimes crescent-shaped. Often they have a sharp dark outline, which is a consequence of their convexity. When etched with the above-mentioned mixture these formations behave very stably. Thus, after 25 seconds of etching they remain absolutely unchanged. The crescent shape of some of them, their color, degree of relief, and resistance to etching identical with that of spores give some basis for considering them fragments of spore coats.

Spores in general are very poorly developed in our coal and are observed as isolated rare inclusions immersed in the main structureless mass of clarite. Among the most widespread types of spores in our coal…

Only small lilac-gray formations, having an irregular shape and serrated edges, belong here (Fig. 24). These spores are usually observed scattered in the main structureless mass of clarite, and only rarely can they be seen grouped together in numbers of 3–4 individuals. Among other spores one may note a very large oval spore of gray color, shown in Fig. 8.

In addition to the organized plant elements listed above, the composition of clarite includes very numerous undetermined inclusions, also of organic origin, oval in shape, structureless in appearance, and light-gray in color. The latter color is identical with that of the main clarite mass. These inclusions are observed chiefly in the form of accumulations, sometimes of rather considerable size (Figs. 16, 17). After etching with a mixture of chromic and sulfuric acids they are preserved, but change their color from light gray to yellowish. In addition, some of them, probably spores, reveal a fine-meshed structure; others show a spherically convex center and a rather broad, even rim (Fig. 19). But most of these inclusions remain structureless after etching and, in their shape and mode of occurrence, are very similar to resin bodies (Fig. 18).

The organized formations described above are distributed unevenly in the main mass of the clarite. Some areas of the clarite consist of the main structureless mass, with preserved cuticles and accumulations of light-gray oval bodies immersed in it. Other, more numerous areas consist of the main structureless mass, in which there are very few preserved cuticles and light-gray bodies, but many other organized formations, such as lilac-gray spores, algae (?), fragments of plant tissues, and so forth.

It is interesting, however, that areas of clarite not containing organized formations, except for cuticle and accumulations of light-gray bodies, after etching with a mixture of chromic and sulfuric acids reveal in many places a fine- and coarse-cellular structure. At the same time, the fine-cellular structure appears where thin cuticles are developed, and the coarse-cellular structure where large cuticles occur (Figs. 20, 21, 22, 23).

Thus, areas devoid of structural inclusions often represent strongly altered, as it were vitrinitized, plant tissue (filled with colloidal organic matter) and containing a large quantity of cuticle. Such areas should be called pure clarite, in contrast to areas saturated with various organized formations.

Areas of clarite saturated, in addition to cuticles and light-gray oval bodies, also with other organized inclusions, before etching consist of a main structureless vitrite-like mass, into which are included cuticles, fragments of cuticles, accumulations of light-gray oval bodies, fragments of fusitic and xylitic cellular tissue, spores, spore coats, mineral inclusions, plant fibers, and a series of other inclusions whose nature is unclear. All these organized formations are also characteristic of durite. But after etching, in the main mass of such claritic areas there are also found small, yet rather numerous, islands with a clear cellular structure. These islands represent vitrinitized cellular areas, as though previously hidden in the main structureless mass, similar to the main mass of durite. The similarity of the latter areas of clarite to durite, observed both in the organized inclusions and in the main mass, and at the same time the presence in them of vitrinitized tissue characteristic of clarite, compels one to call these areas clarito-duritic.

Clarito-durite portions constitute a series of successive transitions from the deprivation of formed elements of pure clarite to durite. The transition of the former into the latter is expressed microscopically by a gradual decrease in the number of vitrinitized cellular areas. The greater or lesser content of such vitrinitized cellular areas in clarito-durite should probably determine one or another of its coking capacities, increasing with an increase in their content. Clarito-durite, as an independent ingredient, in view of obvious difficulties, was not counted by us, but was assigned either to clarite or, chiefly, to durite.

Durite, represented macroscopically by more or less dull varieties of coal, under the microscope shows a great affinity to clarito-durite. It is distinguished by a more varied composition of spores, and also by a greater saturation with formed structures, with the exception, however, of preserved cuticles and light-gray oval bodies, which are less numerous here. The most essential difference of durite consists in the fact that its principal structureless mass, after etching, reveals extremely few hidden cellular areas, being composed almost entirely of colloidal organic mass. Great attention is also merited by the abundance in duritic coals of spores, the special study of which may provide an idea of the primary mother substance of the Minusinsk coals.

Among mineral inclusions in coal, we recorded under the microscope: 1) sulfides, 2) ferruginized areas, 3) clayey interbeds, 4) calcite, and 5) other mineral inclusions, the nature of which remained insufficiently clarified.

Sulfides occur as sparse small grains in the structureless mass of durite and clarite; sometimes they fill individual cells of fusite and xylite tissues.

Ferruginized areas are observed mainly in durite, more rarely in clarite, and very rarely in fusite and xylite tissues, in the form of large and small concretions. They have an oval (oolitic grains) and lenticular form, with a more or less broad shadow rim, a commonly ragged outline, and a light-gray color; they display, as it were, a cellular structure with rare and irregularly scattered oval cells. These areas often contain pyrite grains, fragments of spores, scraps of fusite and xylite tissues, cuticles, and other formed elements (Fig. 7). Sometimes ferruginous concretions capture more or less considerable areas of fusite tissue, impregnating and, as it were, cementing it. After etching with a mixture of chromic and sulfuric acids, the concretions become strongly altered, becoming completely black.

Clayey interbeds under the microscope appear as black opaque bands, small lenses, and fragments, always oriented strictly according to the bedding.

Calcite is usually observed as a filling mineral mass in fusite and xylite tissues, along cracks, and also in some spores. Its color under the microscope is dark gray.

To the group of other mineral inclusions are assigned small dark-gray oval inclusions, usually sharply outlined, sometimes with a rather broad shadow belt. The presence of such a shadow belt indicates a considerable relief and, at the same time, the hardness of these inclusions.

After a general characterization of the principal ingredients, we shall proceed to the description of individual types of coal.

Group of Bright Coals

The first variety of bright coal, or clarito-duritic coal, is composed chiefly of durite, which accounts for up to 66% of it. Of the other ingredients, the greatest role is played by clarite, contributing 21%, and vitrite—10%. Fusite makes up only 1%. Mineral inclusions visible under the microscope amount to 0.5%.

In the composition of the durite, 91% is accounted for by the main structureless mass, and only 9% by various structured elements. Such a high percentage of the main mass in the durite, as well as the comparatively large content of clarite and vitrite in the coal, explain the macroscopically strong luster of this coal.

The rather large content of clarite is due to the development in the coal of a considerable quantity of cuticles and, especially, accumulations of light-gray oval bodies, which make up the bulk of the structured elements in clarite. Thus, of the 21% of clarite (according to Table No. 2), more than 3% is accounted for by accumulations of light-gray bodies, approximately about 1% by cuticles, and only fractions of a percent by “other structured inclusions.”

The second variety of bright coal, or durito-claritic coal, is composed mainly of durite, which makes up as much as 78% of its volume. The main structureless mass in the durite of this coal accounts for about 90%, and the structured elements for 10%. Among the latter, a considerable quantity of large spores is characteristic. In comparison with the preceding variety, the content of vitrite and clarite is much reduced here and, conversely, the content of fusite and xylite is noticeably increased (Table No. 2). Mineral inclusions, such as, for example, concretions of iron oxides, pyrite, etc., are poorly developed in this coal. But mineralization of the fusitic tissue is a rather frequent phenomenon in the coal.

The third variety of bright coal likewise consists chiefly of durite, which gives 67% and consists 90% of the main structureless mass and only 10% of structured formations. Clarite and vitrite occupy a subordinate position in this coal. The former gives 2%, and the latter 7%. Fusite amounts to 8%. A noticeable increase in the content of vitrite and fusite, as well as of mineral inclusions, which here reach 5%, is the characteristic difference of this variety from the preceding one. The mineral inclusions are represented chiefly by concretions of iron oxides (3%) and by clayey interlayers and lenses, which, together with other mineral formations, amount to about 2%.

This variety, in general, in its petrographic composition stands close to the preceding one. However, the considerable content in the coal of mineral inclusions in the form of concretions of iron oxides and clayey interlayers compelled us also macroscopically to distinguish this coal as an independent variety, as a mineralized durito-claritic coal.

Group of Dull Coals

The first variety of dull coal is composed essentially of durite (72%), which here is strongly saturated with structured formations. The latter contribute 21%, while 79% is accounted for by the main structureless mass (in relation to the total thickness of the coal, respectively—15% and 57%; see Table No. 2). The increase in the number of structured formations occurs mainly at the expense of small fragments of cuticle, small fragments of plant tissue, and partly of spores and spore coats. The participation of vitrite and fusite in the composition of this coal is approximately the same as in the II and III varieties of bright coal (Table No. 2).

Table 1

Microscopic composition of coals from seams of the Minusinsk basin (%)

Main groups of coals by maceral analysis: by basin	Main groups of coals by maceral analysis: by nature	Name of coal type	Basic structureless mass	Spores	Algae	Small fragments of cuticles, fusites, and xylitic tissue, etc., formed bodies of organic origin	Total formed bodies	Total durite	Basic structureless mass	Layered structure or small fragments of formed bodies	Total	Vitrite I	Xylite I	Xylite II	Total	Pure fusite	Mineralized fusite	Total	Staining by iron oxides	Other mineral inclusions	Total	Grand total
Balakhta coals	Clarite-durite	I type	60	fractions of %	0.6	5	6	66	17	4	21	10	fractions of %	1	1	1	—	1	—	—	—	100
Balakhta coals	Durite-clarite	II type	70	fractions of %	—	8	8	78	1	4	5	6	1	10	5	6	1	1	—	—	—	100
Balakhta coals	Durite-clarite	III type	60	fractions of %	0.3	7	7	67	2	fractions of %	3	7	8	11	1	7	1	8	3	2	5	100
Matveev coals	Durite	I type	57	1	0.3	14	15	72	—	—	—	6	4	11	15	5	fractions of %	5	1	—	1.5	100
Matveev coals	Durite	II type	58	fractions of %	—	9	10	68	—	—	—	13	fractions of %	1	1	13	fractions of %	12.6	3	1	4	100
Matveev coals	Durite	III type	20	1	0.5	65	66	86	—	—	—	1	1	5	6	4	—	4	1	2	3	100
Matveev coals	Durite	IV type	18	2	0.9	41	44	62	—	—	—	2	14	16	16	—	—	—	4	—	4	100

This rank is characterized by an increased content of xylite of type I, which here occupies second place after durite and amounts to 11%. In addition, the complete absence of clarite is characteristic, which is also observed in the other ranks of dull coal. In connection with the absence of clarite, clarite-durite decreases here, and in ranks III and IV it almost entirely disappears. Of the mineral inclusions, only concretions of iron oxides are fairly numerous—1.5%; the remaining mineral inclusions are generally poorly developed here.

The second rank of dull coal occupies a somewhat distinct position. In terms of the content of vitrite and the main structureless mass in the durite, it belongs rather to the first rank. But in terms of the content of fusite and mineral inclusions, it approaches the most mineralized, fourth rank (Table No. 2).

We nevertheless retain for it second place in the group of dull coals, as required by its characteristic weak luster, which is associated with the structureless mass of durite and a considerable content of vitrite.

Durite constitutes the main mass of this coal, amounting to 68%. It is distinguished by a small content of formed bodies (only 14.5% relative to the total content of durite).

Vitrite here amounts to 13% and, under the microscope, is often observed as rather large lenses and interlayers with a strongly fissured surface.

Fusite, also yielding 13%, is almost completely mineralized. It is distinguished by a fine-, medium-, and large-cellular structure and is usually thin-walled. In the main mass of the coal, fusite forms lenses and interlayers, more rarely separate fragments.

A characteristic feature of this coal is its high mineralization. At the same time, the mineralization affects not only almost all cellular areas of fusite, but also a significant part of the spores. To this must be added a fairly large number of independent mineral inclusions, such as concretions of iron oxides, sulfides, clayey formations, etc. The most numerous among them are concretions of iron oxides (Table No. 2).

The third rank of dull coal already consists of 86% durite. The durite in it is characterized by an extremely large number of formed bodies, which constitute 77% in relation to all the durite. In the composition of these bodies the chief place is occupied by small fragments of cuticle, followed by yellowish-white spores, spore coats, small fragments of fusite and xylite cellular tissue, plant fibers, fragments of individual cells, and also organic inclusions of unclear nature.

The content of vitrite and fusite, in comparison with the other ranks of dull coal, is the lowest here (1% and 4%). Vitrite is developed as sparse and small lenses. Fusite is observed as rare but rather large lenses, often with a very well preserved fine-cellular structure. Very little large-cellular fusite was noted.

Of the mineral inclusions, the most numerous are small, dark-gray inclusions, predominantly oval in shape. These inclusions have broad dark outlines. They are distinguished by great hardness, show no signs of plant structure, and are very resistant to etching with a mixture of sulfuric and chromic acids.

The fourth rank of dull coal consists of 62% durite. In composition, the latter is generally identical with the durite of the preceding rank, but differs from it in a somewhat lower content of formed elements (71% as against 77%).

A considerable part in the composition of this rank is taken by fusite and xylite of the first type, as well as by mineral inclusions (Table No. 2). Fusite and xylite of type I are observed in polished sections as interlayers, lenses, and [[unclear: word cut off at page bottom]].

with large fragments of coarse-, medium-, and fine-cellular structure. Fusite tissue often proves to be thick-walled, and a number of cells are filled with a yellowish organic mass. Such fusite represents a transitional stage toward xylite of the 1st type. Mineral inclusions are represented almost exclusively by concretions of iron oxides, usually in the form of not large oolitic grains of brown iron ore. Other mineral inclusions are very poorly developed.

The durite of the type described and of the preceding type is so strongly saturated with various formed formations that it is entirely unnecessary to speak of any presence in their main mass of hidden (vitrinitized) cellular areas. The durite of both types may therefore be considered the most typical and at the same time the most ash-rich ingredient in the coal of the seam. Weak luster, a high content of fusite, xylite, and mineral inclusions, as well as the high ash content of durite, determine the fourth type as occupying the last place among the series of dull coals.

The coals described above, in addition to macro- and micro-study, were also examined with respect to their specific gravities and technical properties, and also with respect to caking capacity. The results of the determination of specific gravities¹ are presented in Table No. 3 and give us a rather consistent dependence of specific gravity on the composition of the coal.

3. Characterization of coals by specific gravity and technical properties

It turns out that the less the coal is saturated with various formed elements and mineral inclusions, and the more vitrite, clarite, and the principal structureless mass of durite it contains, the lower its specific gravity. Conversely, the fewer of the latter components and the more, at their expense, mineral and formed formations it contains, the higher the specific gravity of the coal. Macroscopically this dependence is expressed as follows: the duller the coal, the higher its specific gravity.

The only exception to this rule is sometimes the bright coal of the 1st type. This type is distinguished by a stronger luster than, for example, the 3rd type of dull coal; however, in individual cases its specific gravity is higher than that of the latter. This, however, does not violate the regularity formulated above between specific gravity and luster, since the average value of the specific gravity of coal of the 1st type is lower than that of the 3rd type, and the indicated cases of increased specific gravity should be explained by the secondary phenomenon of enrichment of the coal with mineral impurities.²

To obtain a more precise idea of the technical properties of the coals, several samples were selected for analyses, except for some of the most homogeneous coals (vitrite coal), as well as of the 2nd and 3rd types of dull coals.

It is evident from Table 4 that the content of moisture and volatiles³ in the different types of coal is not subject to any regularity. The ash content changes more regularly by type, increasing successively from the brighter to the duller coals. Some deviation here is shown by bright coal of the 3rd type and dull coal of the 2nd type. Being strongly mineralized, they stand out sharply for their high ash content. As is known, the higher the ash content, the lower the caking capacity of coal, and vice versa. Therefore the brightest coals, while at the same time being the least ash-rich, are distinguished by the best caking capacity, whereas the most ash-rich—dull—coals do not cake at all.

¹ Determination of specific gravities was carried out in aqueous solutions, of different concentration, of zinc chloride.

² See Table 3 on p. 22.

³ By volatile content here is meant that in the combustible mass of the coal.

Table No. 3.

Specific gravities of coals from the Gigant seam

No.	Coal name	Number of determinations	Extreme values of specific gravities	Mean values of specific gravities	Note
1	Vitrain coal	5	1.14–1.19	1.16	—
2	Bright coal of the 1st kind (clarito-duritic)	56	1.17–1.28	1.21	Specific gravity 1.19–1.21 predominates
3	Bright coal of the 2nd kind (durito-claritic)	23	1.19–1.31	1.22
4	Bright coal of the 3rd kind (durito-claritic with an admixture of fusain, mineral inclusions, and vitrain)	28	1.18–1.67	1.40
5	Dull coal of the 1st kind (duritic)	58	1.20–1.37	1.24
6	Dull coal of the 2nd kind (duritic coal with an admixture of mineral inclusions and partly vitrain)	10	1.30–1.50	1.38
7	Dull coal of the 3rd kind (duritic)	8	1.25–1.50	1.30
8	Dull coal of the 4th kind (duritic coal with small inclusions of fusain)	23	1.25–1.68	1.43	The coal is strongly saturated with various formed elements, including small mineral inclusions (chiefly concretions of iron oxides)

Vitrain coal is characterized by the lowest yield of volatiles, the lowest ash content, and possesses noticeably better caking capacity. Its coke button has approximately the same color and strength as the coke buttons of bright coals of the 1st and 2nd kinds, and gives a weak kidney-shaped swelling in the center. However, it must be noted that the caking capacity of the vitrain of the Gigant seam is considerably lower than the caking capacity of vitrains from a number of Prokop’evsk seams, as well as from the Serebrennikov seam of the Leninsk deposit of Kuzbass.

Bright coals of the 1st and 2nd kinds possess a high content of volatiles (40–45%), a somewhat increased ash content in comparison with vitrain, and a somewhat reduced caking ability. The coke buttons of these coals are dark gray in color, are not swollen, and are fissured.

The increased ash content in these coals may be attributed 1) to individual small mineral inclusions, 2) to the probable, but invisible at the magnification used (×100), fine mineralization of the plant remains present here, and, finally, 3) to the finest mineral admixture in the main mass of durite, not taken into account because of its small magnification. The high yield of volatiles in these coals can petrographically be explained by the substantial content in them of resin bodies, cuticle, algae, and spores. The caking capacity of the first two kinds of bright coals is substantially due to the considerable content in both of them of vitrain, which is observed here not only

in the form of separate lenses and interbeds, but it also composes the main mass of clarite and a considerable part of clarito-durite, as was indicated above.

Bright coal of the IIIrd type, being by its nature a durito-clarite coal and at the same time strongly mineralized, gives very sharp fluctuations in ash content and in the character of the coke. In some cases, in this respect, it approaches the bright coals of the Ist and IInd types, while in others it differs sharply from them, showing several times higher ash content and a complete absence of caking capacity. Evidently, removal of the mineral impurities from this coal could increase its caking capacity.

In volatile-matter content this type gives rather strong fluctuations, but on the whole it is somewhat inferior to the bright coals of the Ist and IInd types.

Dull coal of type I has a volatile-matter content close to that of the preceding type, considerable ash content, and weak caking capacity. The ash here gives lower percentages than in some samples of bright coals of type III, but it has smaller fluctuations, which indicates a fairly uniform distribution of it in the coal. The considerable ash content in this coal is due mainly to the fine mineralization of many cellular areas. The weak caking capacity of the type is a consequence of 1) its considerable graininess and 2) the reduced content in it of vitrite, both in the form of separate lenses and in the form of small areas concealed in the main mass of durite.

Table 4.

Technical analyses of coal from the Gigant seam.

No.	Name of coal	\(W^a\)	\(A^d\)	\(V^g\)	\(K^g\)	\(V^g\)	\(K^g\)	Character of the coke button
1	Vitrite coal	4.90	0.95	35.57	59.53	37.77	62.23	Caked, with cracks
2	Bright coal of type I	4.48	5.70	40.05	55.47	44.58	55.42	Weakly caked
3	Bright coal of type I	4.06	2.67	40.21	55.73	43.11	56.89	Caked, with cracks
4	Bright coal of type I	5.04	1.91	41.11	53.85	44.16	55.84	Caked, with cracks
5	Bright coal of type II	5.12	6.80	35.23	59.65	39.99	60.01	Caked, with cracks
6	Bright coal of type II	5.76	4.84	39.28	59.46	43.54	56.46	Caked, with cracks
7	Bright coal of type III	2.94	24.99	31.12	66.34	43.19	56.81	Not caked
8	Bright coal of type III	4.86	4.75	34.45	60.69	38.11	61.89	Weakly caked
9	Bright coal of type III	3.46	3.92	36.82	59.72	39.75	60.25	Weakly caked
10	Dull coal of type I	4.68	10.07	33.80	61.52	39.64	60.36	Weakly caked
11	Dull coal of type I	4.16	12.26	35.55	60.29	42.53	57.47	Weakly caked
12	Dull coal of type I	4.94	15.65	35.02	60.04	44.22	55.78	Weakly caked
13	Dull coal of type I	3.96	13.48	32.07	63.97	38.84	61.16	Weakly caked
14	Dull coal of type II	3.38	18.26	38.45	58.17	49.06	50.94	Not caked
15	Dull coal of type III	4.20	16.76	30.74	65.06	38.89	61.11	Not caked
16	Dull coal of type IV	2.90	29.30	31.51	65.59	46.47	53.53	Not caked

Note: The analyses were carried out in the laboratory of the SPhIM (former chemical laboratory of the Tomsk Railway); the characterization of caking capacity was also given there.

Dull coal of type II is distinguished by a very high content of volatile matter, a high ash content, and the absence of caking capacity. The high ash content and non-caking character of the coal are explained by its strong mineralization, which under the microscope is expressed in the form of fragments of cells and spores filled with mineral matter, and of numerous cracks, as well as in the form of concretions of iron oxides that are fairly widespread in the coal. There is little basis for attributing the non-caking character of this type to an insufficient content of vitrite, since the latter is present here in a volume no smaller than in the bright coals.

The large yield of volatile matter can to a certain extent be connected with the ferruginous compounds widespread in the coal, which decompose during coking.

Dull coal of type III is characterized by a somewhat reduced yield of volatile matter, a high ash content, and the absence of caking capacity.

Dull coal of type IV is the most ash-rich (29% calculated on laboratory fuel). In its organic mass it yields up to 46% volatile matter and shows no signs of caking. The high ash content of this type is partly due to the mineralization of certain cellular fragments, but is chiefly caused by the strongly widespread concretions of iron oxides in the coal and by fairly numerous fine mineral inclusions.

The large yield of volatile matter is explained chiefly by the considerable content in the coal of spores and their fragments, fragments of cuticle and algae, and, apparently, of undetermined small lilac-gray fragments (partly spores), whose role in the composition of the type is very substantial.

The absence of caking capacity both in this type and in the preceding types must be attributed not only to their ash content, but also to the very small content of vitrite in both, and, conversely, to the large quantity of various form elements, which are elements that lower the caking capacity of the coal.

On the basis of the data of technical analysis, we can roughly divide the petrographic constituents of the seam according to caking capacity into three groups: 1) vitrite, 2) structureless colloidal mass, and 3) form elements. Vitrite, as the technical analyses have shown, possesses the best caking capacity; therefore, its substantial content in the bright, clarite-durite and, especially, clarite coals must be assumed to determine their comparatively satisfactory caking capacity. Conversely, the low content of vitrite in the dull (durite) coals explains to a considerable extent their non-caking character.

The structureless colloidal mass, which constitutes the main field of clarite-durite and partly of clarite, probably also possesses a certain binding force, but this is already less than that of vitrite. This is evident from the example of dull coal of type I, which, having a large percentage of structureless colloidal mass and relatively little vitrite, gives, in comparison with the bright types, weak caking capacity. True, the weak caking capacity of the type is also due to the increased content in it of ash and form elements; nevertheless the content of structureless mass here is so great that, if it had a binding force equal to that of vitrite, it would fully compensate for the negative effect on caking of mineral and form inclusions.

The supposition of a reduced caking capacity of the structureless colloidal mass is also supported by its peculiar role in the structure of the coal, where it seems to cement various, partly drifted material in the form of spores, small plant fragments, fragments of quartz grains, and other mineral inclusions. Since this is so, with stronger

at magnifications than those used by us (×100), in the structureless mass there are probably also smaller plant remains—in particular, for example, pollen—as well as more finely dispersed mineral material.

In Table No. 6 below, the structureless colloidal mass is therefore separated by us into a special group, distinct from the clearly caking vitrite and clarite.

All formed elements of organic origin observed in durite and clarito-durite, as well as xylite and fusite, are elements that reduce the caking capacity of the coal. It is precisely in this connection that the dull varieties of coal in the given seam, characterized by an extremely high content of formed elements, lack caking ability. This latter fact cannot be attributed solely to their high ash content, since the ash content in some of them (dull coal of type III) differs only slightly from the ash content in coals comparatively little enriched in formed formations (dull coal of type I).

Experimental coking of mixtures of ingredients

To elucidate the question of how the addition of a thinning impurity affects the caking capacity of coal from the Gigant seam, the following experiments were carried out. To an average seam sample of coal, successive additions of a thinning impurity were made in the form of 2%, 5%, and, finally, 20% fusite. These mixtures were then subjected to coking in crucibles, and in each of them the volatile-matter content was determined.

It turned out that the addition of fusite in an amount of 20% had only a very slight effect on the yield of volatiles, reducing it by only 2.6%, and did not improve the caking capacity of the coal at all. The addition of fusite in amounts of 2% and 5% had no effect at all on the caking capacity of the coal and only a very weak effect on the yield of volatiles. Moreover, the addition of 2% fusite even seemed to promote a higher yield of volatiles (see Table No. 5). This latter circumstance, however, may be attributed to insufficiently uniform distribution of the material in the average coal sample with which it was necessary to work.

The average seam sample of coal was taken in the form of powdery coal fines obtained as a result of successive sawing of all coal hand specimens available for this seam. The sawing—or, more precisely, the cutting—of the hand specimens was carried out with a hand saw perpendicular to the bedding and through the entire thickness of the specimen. The cut was made to a depth fixed for all specimens, usually 1–2 cm. In order that the material should enter the sample uniformly from the entire thickness of the specimen, the surface of the cut was first leveled. The coal powder obtained from under the saw was collected, sieved through fine sieves (with the aim of isolating larger pieces of coal that had accidentally fallen from the edges of the cut), and then, after thorough mixing, was sent for technical analyses.

Table No. 5

Results of crucible coking of mixtures of an average seam sample of coal with fusite from the Gigant seam of the Chernogorsk deposit

No.	Sample description	Yield of volatiles	Character of the coke button
1	Mixture of the average seam sample of coal with 2% fusite	39.68	Did not cake.
2	Same, with 5%	37.54	Did not cake.
3	Same, with 20%	36.89	Did not cake.
4	Average seam sample of coal	39.51	Did not cake.

Petrographic study of the Gigant seam makes it possible to elucidate the relationship between the macro- and micro-features, specific gravities, and technical properties of the different kinds of coal that we have distinguished in this seam.

This relationship can be traced in Table No. 6; from it one can see that the dullest coals are those that contain many formed elements, then have a high specific gravity, high ash content, and are characterized by the poorest caking capacity. Conversely, the most lustrous coals contain either very few formed formations (clarite-durite coal) or none at all (vitrite coal), have a lower specific gravity, lower ash content, and cake better. Dull coal of the first kind, occupying an intermediate position in luster, is also intermediate with respect to the properties indicated above. This regularity is disturbed only by strongly mineralized lustrous coal of the third kind and dull coal of the second kind. Owing to mineralization, these coals stand out sharply from their neighbors by their elevated ash content, poorer caking capacity, and higher specific gravity.

Table No. 6.

Summary table of the petrographic and technical composition and specific gravities of the coal of the Gigant seam of the Chernogorsk deposit of the Minbass.

Name of kinds of coal	Principal macroscopic features of the coal	Structural microscopic features of the coal	Percentage content of caking ingredients: vitrite and base mass of clarite	Percentage content of caking ingredients: base mass of durite	Technical properties: volatiles \(V^r\)	Technical properties: moisture \(W^r\)	Technical properties: ash \(A^r\)	Coke character	Specific gravity of coal
Vitrite coal	Black, strongly glassy-lustrous, fissured, of homogeneous composition; fracture flat-conchoidal	Before etching, completely structureless, broken by numerous cracks, contains no inclusions. After etching it reveals a distinct coarse- and fine-cellular structure . . . .	100	—	35.57	4.90	0.95	Caked, fissured, steel-gray in color	1.16
1st kind of lustrous coal (clarite-durite)	Black, luster resinous, of clear banded composition. Fracture uneven; coal only slightly fissured	Consists mainly of thinly alternating bands and areas of vitrite, clarite, and little saturated with formed inclusions of durite. Many algae, resin bodies (?) and cuticles . . . .	27.0	60.0	40.50	5.04	1.91	Weakly caked, fissured, steel-gray in color	1.21
2nd kind of lustrous coal (durite-clarite)	Black, luster moderate, resinous. Fracture uneven; coal rather strongly fissured. Banded composition is noted	The principal components composing the coal are the same as in the preceding one. But here a considerably larger quantity of duritic areas is observed . . .	6.0	70.0	37.25	5.44	5.42	Caked, fissured, steel-gray in color	1.22

Name of coal varieties	Principal macroscopic indicators of the coal	Structural microscopic indicators of the coal	Vitrinite and main mass of clarite, %	Main mass of durite, %	Volatile matter \(V^r\)	Moisture \(W^a\)	Ash \(A^r\)	Coke character	Specific gravity of coal
III-rd variety of lustrous coal ([[unclear: clarite-vitrinite]]?)	Consists of alternating main bands of dull and weakly lustrous coal and less large and numerous lenses of brightly lustrous and resinous coal, as well as small fragments of fusainized coal. Fracture fine, uneven, to earthy. Luster uneven. The coal contains many oolitic grains of brown iron ore.	Consists mainly of thin alternating bands and areas of durite, vitrinite, clarite, and fusite. Also contains accumulations of iron oxides. Durite predominates markedly over all other components and is characterized by a relatively low saturation with formed elements.	9.0	60.0	34.13	3.75	11.22	Weakly sinters, steel-gray in color	1.40
I-st variety of dull coal (duritic, banded)	Dark gray, weakly lustrous, banded. The coal consists of thin alternating main dull and subordinate weakly lustrous bands, as well as of sparse bands of vitrinite and fusite. Fracture uneven.	Mainly composed of durite, considerably richer in formed elements than the durite of the preceding variety. A rather large percentage of xylite of types I and II. Next in percentage content come fusite and vitrinite.	6.0	57.0	34.11	4.43	12.82	Weakly sinters, dark-gray in color	1.24
II-nd variety of dull coal (duritic coal, mineralized)	Semidull, with a faint shimmering luster. Composed of a dense, granular-looking mass of black-brown color. Fracture comparatively even. There are sparse but fairly broad and clearly expressed bands of vitrinite.	Composed essentially of durite, which is weakly saturated with formed elements, but is rich in small mineralized fissures. In addition to durite, a significant percentage is made up by clarite, vitrinite, and mineralized fusite.	13.0	58.0	38.45	3.81	18.26	Powder of dark-gray color	1.33

Name of coal types	Main macroscopic characteristics of the coal	Structural microscopic characteristics of the coal	Vitrinite and basic mass of clarite	Basic mass of durite	Volatile matter \(V^r\)	Moisture \(W^r\)	Ash \(A^r\)	Coke character	Specific gravity of coal
III type of dull coal (duritic, massive)	Coal almost dull, with a weak greasy luster, homogeneous composition, dark-gray color. Hard, has an uneven fracture	Durite predominates, extremely strongly saturated with small fragments of formed elements of organic origin and partly with small mineral inclusions	0.6	20.0	30.74	4.20	16.76	Dark-gray powder	1.30
IV type of dull coal (durito-fusitic)	Dull coal, analogous to the preceding one, but strongly enriched with small inclusions of fusite	The petrographic composition is almost the same as in the preceding coal. It differs in a higher content of fusite and xylite of type I, and also in a rather large number of concretions of iron oxides	2.0	18.0	31.51	2.90	29.30	Powder of dark-gray, almost black color	1.43

Despite the fact that the most lustrous clarito-duritic and durito-claritic coals and vitrite give the best caking capacity in the seam, it is lower in them than in these same ingredients in the Serebrennikovsky seam of the Leninsk deposit of the Kuzbass. The reduced caking capacity of the vitrite and lustrous coals in the seam described may be explained by: 1) the considerable oxidation of the coal (the samples were taken in the weathering zone), 2) the younger physicochemical age of the coal, 3) different physicochemical conditions of transformation of the coal mass, and 4) different original plant material of the coals.

The difference in the original plant material is revealed to a certain extent when etching vitrites in both seams. The vitrite of the Serebrennikovsky seam often shows the structure of woody tissue, in which annual rings can not infrequently be suspected. The vitrite of the Gigant seam, on the contrary, usually reveals a structure more similar to the cellular structure of herbaceous plants. This is visible, for example, in Fig. 21, where part of a leaf or stem of a herbaceous plant is shown. The small size of the vitrite lenses may also indicate this to a certain extent. Here they usually do not exceed 3 mm in thickness, whereas in the Serebrennikovsky seam their thickness often reaches two and even three centimeters. It cannot be assumed that the small size of the vitrite lenses in the Gigant seam resulted from greater destruction and more deeply advanced processes of coalification of the plant matter here, since the degree of preservation of plant remains in the coal of this seam is not only lower, but even somewhat higher than in the coal

of the Serebrennikov seam. In the formation of the coal of our seam, apparently, herbaceous and leafy material took an essential part, as is indicated by the high content in it of cuticle remains. The peculiar spore composition of the Gigant seam also deserves attention; some idea of it is given by the photographs in Figs. Nos. 8 and 9 and Fig. 24.

Let us note further that the coal of the seam described, as mentioned above, in some of its layers (bright coal of the III kind, dull coal of the II kind) is strongly mineralized. This speaks of the distinctive conditions of formation of the seam and, to a certain extent, explains the poor caking capacity of the coal. In the latter respect it should especially be noted that the mineral admixture here occurs in a finely dispersed form. And from experiments with fusite it is known that the more finely dispersed the lean admixture is in coal, the lower its caking capacity. The removal of these mineral admixtures from the coal should therefore constitute a task for the preparation engineer.

Finally, it deserves attention that an increase in mineralization, especially in the dull coals of the seam, is usually accompanied by an increase in the content of fusinitic organic formations. The lowering of caking capacity, both on account of mineral admixtures and on account of formed [[unclear: word obscured]] formations, is summed in this case, and the dull coals of our seam prove to be completely non-caking. Such a coincidence for the Gigant seam is evidently not accidental. From the preceding it is obvious that, in the process of accumulation of the primary plant material of the seam, the phenomenon of drift played an essential role, delivering both mineral material, finely dispersed in the coal, and various formened formations.

EXPLANATIONS TO THE PLATES OF MICROPHOTOGRAPHS

The polished surfaces of the polished sections photographed are perpendicular to the bedding.

Fig. 4. Fine-celled fusite with more or less parallel rows of elongated cells. From dull coal of the III kind. ×100.

Fig. 5. Medium-celled fusite, as in the preceding case, with a parallel arrangement of elongated cells. From dull coal of the I kind. ×100.

Fig. 6. A lens of coarse-celled fusite, outlined by a thick cuticle “aa.” The central part of the lens is represented by xylite of the 1st type with a fine-celled structure. The lens as a whole is probably part of an independent plant organ (for example, a leaf stem). From bright coal of the I kind. ×100.

Fig. 7. Small concretions of iron oxides in durite. From dull coal of the III kind. ×100.

Fig. 8. A macrospore with an opened cavity in durite. From bright coal of the I kind. ×100.

Fig. 9. A lilac-gray alga (?) “a1” and “a2,” close to Pastilus cellulosus of the Velikan seam of the Minbass. The surrounding field is clarito-durite. From bright coal of the I kind. ×100.

Fig. 10. The same area of the polished section as in photograph No. 9, after etching. The alga does not change in color, but reveals a clearer cellular structure (the change in the shape of the right alga “a2” is not the result of etching, but of polishing that preceded it). The etched groundmass of clarito-durite, in areas free of formened elements, also gives a cellular structure. From bright coal of the I kind. ×100.

Fig. 11. A fragment of the same lilac-gray alga after etching. Its individual constituent cells are visible, partly with well-preserved cavities. The surrounding black field is etched durite. Bright coal of the I kind.

Fig. 12. Clarito-durite “aa,” alternating with vitrite “bb.” On the left a thick cuticle “c” is visible. From bright coal of the I kind. ×100.

Fig. 13. Clarito-durite, more than in the preceding case, saturated with shaped formations, in particular small fragments of cuticle. From lustrous coal of the 2nd variety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ×100.

Fig. 14. The central part of the photograph is occupied by a lens of gray xylite of the 2nd type, “aa.” The lens is outlined by a thin cuticle and has a poorly discernible fibrous structure. The left part of the photograph is occupied by two strips of vitrite, separated by a strip of gray xylite of the 2nd type, “b.” The remainder of the field of the photograph is durite with small fragments of light-yellow xylite of the 1st type, “c.” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ×100.

Matte coal of the 1st variety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ×100.

Fig. 15. General view of matte coal of the 3rd variety. A typical durite, in which a characteristically high content of shaped elements and a comparatively small amount of the main structureless mass are observed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ×100

Fig. 16. Accumulation of light-gray oval and elongated bodies—“aa” (presumably resinous). The surrounding field is clarite with thin cuticles. Lustrous coal of the 1st variety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ×100.

Fig. 17. “aa”—an accumulation of the same, but smaller, light-gray oval bodies. The remaining field is clarite containing thin cuticles and individual inclusions of light-gray bodies. From lustrous coal of the 1st variety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ×100.

Fig. 18. Accumulation of light-gray bodies after rather prolonged etching. The surrounding clarite field has partly been etched, and partly has revealed a fine-cellular structure (darkening in the lower part of the photograph is a photographic defect). From lustrous coal, 1st variety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ×100.

Fig. 19. “a”—accumulation of light-gray oval spores in durite-clarite after rather prolonged etching. — From lustrous coal of the 1st variety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ×100.

Fig. 20. Interlayer before etching. Along the edges of the interlayer thick cuticles with denticles directed inward (on the right) are visible. Lustrous coal of the 1st variety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ×100.

Fig. 21. The same vitrite interlayer after etching. A coarse-cellular structure is fairly clearly visible, especially in the left part of the interlayer. The central part of the interlayer has been etched more strongly, which gives it greater similarity to a lens of coarse-cellular fusite (Fig. 6). Along the edges of the interlayer, the main mass of durite has been etched. “a”—cuticle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ×100.

Fig. 22. Clarite with thin cuticles before etching. Lustrous coal of the 1st variety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ×100.

Fig. 23. “aa”—strips of clarite after strong etching. In places a fine-cellular structure appears. “bb”—etched durite. From lustrous coal of the 1st variety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ×110.

Fig. 24. Schematic sketch of a series of small lilac-gray spores. In the drawing one can distinguish spores of two types: “a”—dentate on both margins, and “b”—dentate on one margin. Magnification arbitrary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(Figs. 17, 18, 23, and 24 are not included.)

Fig. 4.

Fig. 5.

Fig. 6.

Fig. 7.

Fig. 8.

Fig. 9.

Fig. 10.

Fig. 11.

Fig. 12.

Fig. 13.

Fig. 14.

Fig. 15.

Fig. 16.

Fig. 19.

Fig. 20.

Fig. 21.

Fig. 22.

II. The Moshchnyi Seam

The collection of coal samples from the Moshchnyi seam was carried out in mine No. 3 of the Chernogorsk mine, at the 25 m level. The sampling site was the corner of the dip and main adits in the western wing of the mine field.

At this place the seam is represented by a single bench with a total thickness of 2.34 m. Sandy-clayey partings of barren rocks range in thickness from 0.3 cm to 4.7 cm, but more often are 0.3–0.5 cm. In total they amount to 10 cm, or 4.3% of the entire thickness of the seam. The roof of the seam is a fine-grained light-gray sandstone; the floor is a thin-plated carbonaceous shale with interbeds of bright coal. Three varieties of bright coal and five varieties of dull coal take part in the composition of the seam. In addition, we distinguish in it especially mineralized coal, as well as vitrite and fibrous coal.

The following macroscopic description of these coals proceeds from the more bright varieties to the dull ones.

1. Group of bright coals

Bright coal of variety I possesses the strongest and fairly homogeneous resinous luster. It has a weakly expressed finely banded texture and a black color. The banded texture of the coal is determined by the alternation of principal bands of resin-bright coal with thin bands of dull and brightly lustrous (vitrite) coal. On planes parallel to the bedding, the coal displays a considerable quantity of fine dull, partly fusitic films, as a result of which on these planes it appears more dull. Fusitic inclusions are few in number and in most cases belong to the hard variety of fusite. The fracture of the coal is uneven, from fine to medium, sometimes flat-conchoidal. The coal is fairly strong and bears comparatively few cleavage cracks. It forms in the seam small interbeds 0.3–1.0 cm thick and, at most, 5.8 cm thick. These interbeds are distributed rather uniformly throughout the entire thickness of the seam (Fig. 25).

Bright coal of variety II, in contrast to the preceding, contains considerably more dull bands, owing to which it appears much less bright, and its luster is less homogeneous. Along the bedding planes the coal is strongly enriched with films of soft and hard fusite; moreover, in contrast to coal of variety I, here both are distinguished by larger size, and the most numerous among them are inclusions of soft fusite. The considerable content of fusitic bands contributes to a weakening of the coal’s strength. The coal may be characterized as of medium strength, containing comparatively many cleavage cracks. It is distributed in the seam in interbeds from 0.3 to 9.0 cm thick.

Bright coal of variety III differs from bright coal of variety II not sharply: it has a somewhat weaker resinous luster, contains somewhat more dull bands, and is still less strong. The content of fusite coal in general, and of its hard variety in particular, remains approximately the same as in coal of variety II.

The coal is distributed in the seam more or less uniformly throughout its entire thickness and is observed in the form of interbeds from 0.2 cm to 4.0 cm thick.

The group of bright coals constitutes, in all, up to 48% of the working thickness of the seam, with the highest content being given by bright coal of variety II—up to 27% (Table No. 7).

Petrographic section of the Moshchnyi seam.

Fig. 25.

Legend

• Vitrain
• Bright coal:
• I kind
• II kind
• III kind
• Dull coal:
• I kind
• II kind
• III kind
• IV kind
• V kind
• Fusain
• Interlayers
• Argillite

Scale: 1 cm = 2 centimeters.

II. Group of Dull Coals

Dull coal, type I has a heterogeneous dull-greasy luster, approaching a weak resinous luster. The color of the coal is grayish-black; the fracture is uneven; the texture is banded. The banding is expressed by an alternation of broader dull and narrow bright bands. Along the bedding planes, fairly numerous, mainly small films of hard, and more rarely soft, fusite are visible. In comparison with the bright coals of types II and III, the coal is somewhat stronger. In the seam it is distributed more or less uniformly throughout its entire thickness in partings from 0.2 cm to 6.0 cm thick.

Dull coal, type II is distinguished by an even weaker luster but greater strength. It is comparatively little broken by cleavage cracks and, when split, gives an uneven fracture of medium coarseness. The bedding surfaces, as in dull coal of type I, contain a large number of small films of hard fusite. It is distributed in the seam in partings from 0.2 to 6.5 cm thick throughout the entire thickness of the seam.

Dull coal, type III in luster approaches dull coal of type II, but differs from it in the character of its composition and in strength. This is a dense and strong coal, almost without cleavage cracks. Its fracture is comparatively even and coarse. The color is grayish-black. The banding in this coal, with alternation of dull and bright bands, owing to the small size and number of the latter, is weakly expressed, and the coal appears comparatively homogeneous. Characteristic of this type is an exceptionally low content of fusite, the inclusions of which usually belong to the hard variety of this coal. In the composition of the seam this type plays a subordinate role and occurs chiefly in the upper part of the seam in the form of several partings of small thickness, from 2.0 to 3.0 cm (see Fig. 25).

Dull coal, type IV has a dark-gray color, dull luster, and homogeneous composition. The coal is strong, not broken by cleavage cracks, and has an uneven, fairly coarse fracture. Along the bedding surfaces numerous films of hard, and in rare cases soft, fusite are visible. It occurs in the seam in partings from 0.5 to 5.0 cm thick in its middle and lower parts.

Dull coal, type V is composed of thinly alternating bands of dull coal and fusite. Sometimes both are interbedded with very small lenses of vitrite, which impart to the coal a weak shimmering luster. The high content of fusite gives this coal an irregular earthy fracture and a low specific gravity. Along the bedding surfaces, fusite is observed as numerous small and usually hard films overlapping one another in various directions.

The coal of this type, despite the large content of fusite, is sufficiently strong and does not have cleavage cracks. This is possibly explained by the fact that the hard fusite films and bands oriented in different directions, as it were, bind the coal and hinder its splitting. In the composition of the seam this coal is observed in the form of several partings from 2.5 to 5.0 cm thick in the lower part, making up in all 5% (Table 7).

The highest content in the seam falls to the share of dull coal of type I (12%) and then dull coal of types II and III (10 and 9%); the lowest is for dull coal of type III (4.0%). The total content of dull coals reaches 40% of the working thickness of the seam.

Mineralized coal is represented in the seam by only a few partings from 1.0 to 3.6 cm. It is distinguished by a dark-gray color, great strength, an almost massive composition, and a high specific ...

Table 7.

Macroscopic composition of the coal of the Moshchny seam of the Chernogorsk deposit

Main groups of coals	Name of macroscopic ingredients and coal types	Probable nature of the coals and barren rock	Thickness of ingredients in the seam, cm	% of the useful thickness of the seam¹
Bright coals	Bright coal, type I	Clarito-duritic	22.6	10.0
Bright coals	Bright coal, type II	Durito-claritic	62.6	27.0
Bright coals	Bright coal, type III	Durito-claritic	28.6	12.0
Matte coals	Matte coal, type I	Duritic	27.7	12.0
Matte coals	Matte coal, type II	Duritic	24.3	10.0
Matte coals	Matte coal, type III	Duritic	9.4	4.0
Matte coals	Matte coal, type IV	Duritic	22.0	9.0
Matte coals	Matte coal, type V	Durito-fusitic coal	10.6	5.0
	Vitritic coal	Vitrite	6.6	3.0
	Fibrous coal	Xylite and fusite	2.7	1.0
	Mineralized coal	Coal–sand–clay mass	7.7	3.0
	Barren rock	Sandy-clayey rock	10.2	4.0
			235 cm	100%

by weight, clearly perceptible even upon simple weighing in the hand. The coal is entirely matte, fine-grained, and by its nature evidently represents a coaly sandy-clayey mass.

Fibrous coal (fusite) occurs as small lens-shaped inclusions and is recorded in greater or lesser quantity in all matte and bright coal types. Usually these small lenses belong to the hard variety of fibrous coal and, under the microscope, will correspond either to fine-cell fusite or to xylite. Very little mineralized fusite was observed macroscopically.

Vitritic coal, like fusite, occurs in most cases as small lenses in all types of bright coal and in three types of matte coal. It was not encountered only in matte coal of type IV. The luster of the vitritic lenses is distinguished by the greatest brightness and has a resinous-glassy character.

¹ By the useful thickness of the seam is here meant the entire thickness of the coal with small mineral partings.

Of the secondary mineral inclusions, only a few inclusions of pyrite and calcite could be observed macroscopically in the coal; both were noted in the form of small films either along bedding planes or along cleavage cracks.

The specific gravities of the above-described coal varieties, as in the Gigant seam, increase successively from the more lustrous to the more dull coals. The only exception here is dull coal of variety V, which, being strongly enriched with barren fusite, gives a lower specific gravity than dull coal of variety IV (Table 8). The mean specific gravities of the lustrous varieties and of the first three varieties of dull coal differ very little from one another (1.18–1.21). This can partly be explained by the same barren fusite, which, occurring in large amounts in the duller coals, lowers their specific gravities. As for the first varieties of lustrous coal, their low specific gravities must be attributed to the considerable content in them of vitrite and clarite.

The varieties of lustrous and dull coals distinguished in the Moshchnyi seam were studied with respect to their technical properties and coking capacity. The data from this study are summarized in Table No. 9.

In technical properties and coking capacity, the coals of the Moshchnyi seam show the same regularities as in the Gigant seam. The best, though weak, coking is given by the lustrous coals, and among them the clarite-durite coals (variety I); the coking capacity of dull coals rapidly decreases from variety I to the subsequent ones, with coals of varieties IV and V, like mineralized coal and fusite, showing no signs of coking. The generally weak coking of the lustrous coals, in addition to a number of factors indicated in the description of the Gigant seam, must be connected above all with the small sampling depth (25 m) and the undoubted influence of secondary oxidation.

Table 8.

Specific gravities of vitrite, lustrous and dull coal varieties from the Moshchnyi seam of the Chernogorsk deposit.

No.	Macroscopic ingredients and coal varieties	Number of determinations	Extreme values of specific gravities	Mean values of specific gravities
1	Vitrite	5	1.15–1.17	1.16
2	Lustrous coal, variety I	20	1.16–1.20	1.18
3	Lustrous coal, variety II	20	1.17–1.22	1.19
4	Lustrous coal, variety III	20	1.16–1.27	1.19
5	Dull coal, variety I	15	1.18–1.22	1.20
6	Dull coal, variety II	10	1.17–1.25	1.20
7	Dull coal, variety III	5	1.19–1.22	1.21
8	Dull coal, variety IV	10	1.24–1.48	1.34
9	Dull coal, variety V	10	1.25–1.32	1.29
10	Mineralized coal	—	more than 1.70	—

Table No. 9.

Results of technical analyses of coal from the Moshchnyi seam

No.	Coal name	$W^p$	$A^p$	$A^c$	$V^p$	$V^r$	$K^p$	$K^r$	Characteristic of the coke button
1	Bright coal, type I	3.35	2.45	2.53	37.88	40.21	58.77	59.79	Weakly caked, grayish-black
2	Bright coal, type I	3.36	2.10	2.17	34.47	36.46	62.17	63.54	Very weakly caked, black
3	Bright coal, type I	4.10	1.60	1.66	37.86	39.51	58.64	60.40	Caked, slightly fused, dark gray
4	Bright coal, type II	3.67	4.25	4.41	33.34	36.21	62.99	63.79	Caked, [[unclear: obscured text]]
5	Bright coal, type II	3.62	2.12	2.20	33.81	35.87	63.07	64.13	Very weakly caked, black
6	Bright coal, type II	3.34	3.92	5.36	35.04	37.78	61.62	62.22	Very weakly caked, black
7	Bright coal, type III	3.20	3.25	3.36	35.69	38.15	61.11	61.85	Very weakly caked, black
8	Bright coal, type III	3.29	1.90	1.96	37.01	39.04	59.70	60.96	Very weakly caked, black
9	Bright coal, type III	3.05	3.08	3.17	34.34	36.50	62.61	63.50	Caking
10	Dull coal, type I	3.31	2.75	2.84	30.93	32.93	65.76	67.07	Caking
11	Dull coal, type I	3.95	2.75	2.85	35.72	38.29	60.33	61.17	Very weakly caked,
12	Dull coal, type I	3.69	3.02	3.14	32.80	35.16	63.51	64.84	Caking
13	Dull coal, type II	4.15	5.89	6.15	29.68	32.99	66.17	67.01	Caking
14	Dull coal, type II	3.39	3.14	3.25	33.76	36.12	62.85	63.88	Caking
15	Dull coal, type III	2.78	12.49	12.85	34.95	41.25	62.27	58.75	Caking
16	Dull coal, type IV	3.48	14.02	14.54	19.74	23.93	76.78	76.07	Non-caking
17	Dull coal, type IV	3.36	10.63	10.99	29.98	34.86	66.66	65.14	Non-caking
18	Dull coal, type V	2.75	16.35	16.71	19.78	24.45	77.38	75.55	Non-caking
19	Dull coal, type V	3.37	9.54	9.97	20.21	23.21	76.42	76.79	Non-caking
20	Mineralized coal	2.31	47.64	48.77	18.23	36.42	79.46	63.58	Non-caking
21	Vitrite coal	1.71	0.89	0.91	14.44	14.83	82.85	85.17	Caked, fused, swollen
22	Hard fusite	1.86	9.94	10.15	20.24	22.95	77.90	77.05	Non-caking

Note: The characterization of the coke buttons was provided by Prof. I. V. Gebler.

III. Velikan Seam.

MACRODESCRIPTION OF THE SEAM.

Samples from the Velikan seam were collected in mine No. 8 of the Chernogorsk mine. The sampling site was the face of the first adit, parallel to the main adit, in its western part. This face was selected as the deepest from the surface (about 50 m).

The coal seam at the sampling site consists of 3 benches. The first (upper) bench has a thickness of 1 m and is separated from the second by an interbed of dark-gray argillaceous-clayey, partly light-gray sandy shale 0.6 m thick. The second (from above) bench has a thickness of 0.27 m and is separated from the third by an interbed of coaly sandstone 0.5 m thick. The third, lowermost bench has a thickness of 0.45 m. The total thickness of the seam is 1.83 m, and the useful thickness is 1.72 m. Fine mineral interbeds, apart from interbeds of mineralized coal, were not observed macroscopically. The roof and floor of the seam are gray, strongly sandy shale.

Macroscopically, the coal of the seam could be divided into seven types: three bright and four dull; in addition, mineralized coal, as well as vitritic and fibrous coals.

The nature of the distribution of these coals in the seam is shown clearly in the petrographic section of the seam (Fig. 26), and the percentage content of the types in the seam is given in Table 10.

Petrographic section of the Velikan seam.

LEGEND:

• Batrayite
• Lustrous coal — type I
• Lustrous coal — type II
• Lustrous coal — type III
• Dull coal — type I
• Dull coal — type II
• Dull coal — type III
• Dull coal — type IV
• Fusite
• Carbonaceous argillite
• Argillite
• Sandstone

Scale:
1 cm = 2 centimeters.

Fig. 26.

From the section and the table it is evident that the seam is dominated by the group of bright coals, with the lower bench of the seam being composed almost exclusively of coals of this group. The role of bright coals in benches I and II is approximately the same; they constitute about 50% of the thickness of each of them.

The group of bright coals as a whole makes up 59.0% of the entire useful thickness of the seam. Its content in the individual benches ranges from 49% in the first and 42% in the second to 94% in the third (Table 10).

Table No. 10.
Macroscopic composition of coal from the Velikan seam of the Chernogorsk mine.

Main coal groups	Name of macroscopic ingredients	Probable nature of the coals	I bench: thickness of ingredients, cm	I bench: % of bench thickness	II bench: thickness of ingredients, cm	II bench: % of bench thickness	III bench: thickness of ingredients, cm	III bench: % of bench thickness	For the seam: thickness of ingredients in the seam, cm	For the seam: % of total useful seam thickness
Bright coals	Bright coal, type I . . . . .	Clarito-duritic	13,6	14,0	1,7	6,0	39,7	87,0	55,0	32,0
Bright coals	Bright coal, type II . . . .	Durito-claritic	30,4	31,0	9,8	36,0	2,9	7,0	43,0	25,0
Bright coals	Bright coal, type III . . . .	Durito-claritic, mineralized with gypsum	4,0	4,0	—	—	—	—	4,0	2,0
Dull coals	Dull coal, type I	Duritic	10,0	11,0	2,5	9,0	0,4	1,0	12,9	8,0
Dull coals	Dull coal, type II . . . .	Duritic	20,0	21,0	11,6	43,0	—	—	31,6	20,0
Dull coals	Dull coal, type III . . . .	Duritic	12,0	12,0	—	—	—	—	12,0	7,0
Dull coals	Dull coal, type IV . . . .	Duritic	1,0	1,0	—	—	—	—	1,0	1,0
	Vitrite coal . . . . .	Vitrite	3,0	3,0	0,5	2,0	2,5	5,0	6,0	3,0
	Fibrous coal . . . .	Fusite and xylite	2,0	2,0	1,0	3,0	—	—	3,0	1,0
	Mineralized coal . . . . . . . .	Carbonaceous-clayey material	1,0	1,0	0,4	1,0	—	—	1,4	1,0
			97,0	100	27,5	100	45,5	100	170,0	100

The strongest bright coal and the most widespread in the seam is bright coal of type I. Its luster is resinous, fairly bright and homogeneous. The color is black; the fracture is uneven, from medium to coarse. The bedding is weakly expressed, very fine, and is manifested by the alternation of more and less lustrous streaks with thin dull ones. The coal is dense, sufficiently hard, and is entirely not broken by cleavage cracks. On the bedding surfaces one can see small films of hard and soft fusite, as well as films of dull coal. Both the one and the oth—

where they are observed here in limited quantities, without exerting much influence on the reduction of luster. In bench III of the seam, this coal accounts for 87% of its thickness.

Bright coal of type II is characterized by a higher content of dull and fusite bands, the latter being especially numerous and clearly visible on the bedding surfaces, where they appear as small, predominantly hard films. The luster of the coal is considerably weaker and less uniform. The fracture is uneven and finer. The color is grayish-black. Bedding is expressed better here and is emphasized by small lenses of fusite. The coal splits well along the bedding, contains cleavage cracks, and in general is less strong.

Bright coal of type III differs sharply from both of the above-described types. It has a weak, nonuniform luster, a coarse-grained structure, a fine uneven fracture, and is distinguished by very low strength and a considerable specific gravity. In addition, it is strongly enriched in thin films of gypsum along numerous cleavage cracks. The presence of these films in the coal probably accounts to a significant extent for its high specific gravity.

The group of dull coals occupies a subordinate position in the seam and is observed only in its upper part, in benches I and II. The total content of the group in the seam is 36%; by benches it is distributed as follows: the first bench—45%, the second—52%, and the third—1%. The most substantial role in the group (Table 10) belongs to dull coal of type II—20%, and an altogether insignificant role to dull coal of type IV—1%. Dull coals of types I and III make up a small and approximately equal content (8.0% and 7.0%).

Dull coal of type I has a weak resinous luster, approaching dull-fatty, a grayish-black color, and a distinct banded structure. If in bright coals (excluding type III, as occupying a special position) bright bands predominate over dull ones, then in the coal being described we see, on the contrary, a decisive predominance of dull bands over bright ones. The coal splits easily along the bedding; on the resulting surfaces, numerous films of hard and, more rarely, soft fusite are visible. Cleavage cracks are observed in the coal in considerable quantity, but they are usually weakly expressed. The fracture is uneven and fine.

Dull coal of type II differs in having a more homogeneous structure, greater density, and a weaker dull-fatty luster. Bandedness is very weakly expressed in it. The bright bands are few and so small that they remain almost imperceptible to the eye. Lenses of fusite, being very thin, are likewise poorly visible on vertical cuts of the hand specimen, although on the bedding surfaces they turn out to be no fewer than in the preceding type. In the overwhelming majority, the fusite inclusions belong to the hard variety and only slightly soil the hands. The color of the coal is dark gray; the fracture is uneven, somewhat coarser than in dull coal of type I.

Dull coal of type III differs sharply from both of the above-described types: it has a homogeneous structure (without any indications of bedding), a coarse uneven fracture, passing in places into flat-conchoidal and in places into fibrous, a dark-gray color, and a homogeneous dull-fatty weak luster. The coal is very dense and strong. Fusite inclusions are completely absent; they were not encountered even on the bedding surfaces.

Dull coal of type IV contains more fine clayey admixture, as a result of which its luster becomes almost entirely dull. The color of the coal, structure, density, and strength remain approximately the same as in dull coal of type III. But the fracture is more uneven and less coarse than in the preceding type.

Vitrite and fibrous coals are observed as small lenses and films in the first two types of bright coal and the first two types of dull coal. In bright coal of type III and in dull coals of types III and IV, vitrite and fusite could not be detected macroscopically. The small size of the lenses of vitrite and fusite made it impossible to take proper account of their percentage content in the seam. In the macroscopic counts, therefore, only a few of the largest of them were included (from 0.5 mm and larger).

It is necessary to note further that vitrite bands, as a rule, most enrich bright coals of types I and II; fusite, on the other hand, enriches types I and II of dull coal, and least of all bright coal of type I. No mineralized fusite was observed macroscopically. However, this does not exclude the possibility of partial mineralization of individual fusite inclusions belonging to its hard variety. Clarification of this question requires microscopic analysis.

The especially mineralized coal distinguished in the Velikan seam is represented by two interbeds in benches I and II. These interbeds have insignificant thickness and play a minor role in the composition of the indicated benches. Macroscopically they may be characterized as interbeds of coal strongly enriched with clayey material.

Mineral inclusions of secondary origin are poorly developed in the seam; among them only films of sulfides and gypsum occur. Both are usually observed along cleavage cracks and predominantly in bright coals of types II and III, as coals with the most clearly expressed fissuring. Films of sulfides are often rather large and frequently have an oval shape. Films of gypsum are, in the overwhelming majority of cases, smaller and always irregular in shape. They occur almost exclusively in bright coal of type II, where they fill numerous cracks cutting the coal in different directions.

Specific gravities and technical properties of the coals of the Velikan seam reveal, in general, the same regularities as the coals of the Gigant seam studied by us in greater detail. The specific gravities of the coals, from the brighter to the duller, consistently increase their average values (Table 11). The only exception here is the bright coal of type III enriched with gypsum, whose specific gravity approaches that of the dullest coals, and also bright coal of type II, whose weight, on the contrary, is lower than might have been expected in comparison with the weight of the brighter coal of type I. The comparatively low specific gravity of bright coal of type II is difficult to explain macroscopically.

Table No. 11.

Specific gravities of vitrite, bright and dull coals from the Velikan seam of the Chernogorsk deposit.

No.	Coal name	Number of determinations	Extreme values of specific gravities	Average values of specific gravities
1	Vitrite coal	5	1.13–1.20	1.15
2	Bright coal of type I	15	1.17–1.24	1.20
3	Bright coal of type II	10	1.16–1.23	1.19
4	Bright coal of type III	5	1.48–1.56	1.51
5	Dull coal of type I	10	1.18–1.24	1.21
6	Dull coal of type II	10	1.22–1.29	1.24
7	Dull coal of type III	5	1.54–1.56	1.55
8	Dull coal of type IV	5	1.56–1.60	1.58

Let us further note that the changes in specific gravities agree fairly well with the composition of the coals described above and established macroscopically. Thus, for example, bright coals, in which much was noted above

thin vitrite bands, give low specific gravities. Dull coals of types III and IV, as well as bright coals of type III containing a fine clayey admixture, are characterized by a higher specific gravity (Table 11). The data of proximate analyses of the coals of the Velikan seam are brought together in Table 12.

Table No. 12.
Proximate analyses of coals from the Velikan seam.

No.	Coal name	W^л	A^л	A^c	V^л	V^г	K^л	K^т	Characteristic of the coke button1
1	Bright coal, type I, bench 3	3,88	2,39	2,48	39,00	41,61	57,12	58,39	Very weakly caking, black
2	Bright coal, type I, bench 2	4,28	1,18	1,23	34,98	36,16	60,74	63,84	Very weakly caking, black
3	Bright coal, type I, bench 3	3,96	2,20	2,25	37,55	40,01	58,52	59,99	Very weakly caking, black
4	Bright coal, type II, bench 2	4,01	4,73	4,92	31,47	34,41	64,52	65,59	Very weakly caking, black
5	Bright coal, type II, bench 1	3,69	2,71	2,81	37,15	39,69	59,16	60,31	Very weakly caking, black
6	Bright coal, type III, bench 2	2,81	32,35	33,28	24,09	37,15	73,10	62,85	Non-caking
7	Dull coal, type I, bench 2	3,15	2,67	2,76	31,77	33,73	65,08	66,27	Non-caking
8	Dull coal, type I, bench 1	3,93	6,76	7,04	27,71	31,03	68,36	68,97	Non-caking
9	Dull coal, type II, bench 1	3,54	8,98	9,51	27,18	31,07	69,28	68,93	Non-caking
10	Dull coal, type II, bench 1	3,76	13,39	13,76	26,25	31,68	69,99	68,32	Non-caking
11	Dull coal, type II, bench 1	3,29	29,41	30,41	16,94	25,17	79,77	74,28	Non-caking
12	Dull coal, type V, bench 1	3,33	3,48	3,59	33,41	35,88	63,23	64,12	Non-caking
13	Vitrite coal	4,70	0,71	0,75	30,03	31,66	65,27	68,34	Weakly caking, black
14	Fusite coal (soft variety)	3,80	4,10	4,25	18,48	20,07	77,72	79,93	Non-caking

From the table it is evident that the caking capacity, as in the other seams, decreases from bright to dull coals. The complete loss of caking capacity by the bright coal of type III finds its simple explanation in the high mineralization of this coal, which gives more than 32% ash.

Attention is further drawn to the very weak caking capacity also of the bright coals of types I and II, despite the fairly great depth of sampling (50 m). In coals of type II, the decrease in caking capacity must to a certain extent be attributed to the considerable content of fusite. But in coals of type I this influence is almost excluded. Their weak caking must therefore be connected with the low degree of coalification, as well as with the probably very great depth of the oxidation zone of the coals of the Minusinsk Basin.

IV. The Dvukh-arshinnyi Seam

MACROSCOPIC DESCRIPTION

Sampling of the seam was carried out in mine No. 8 of the Chernogorsk mines. The sampling site was the coal of the conveyor drift and of the 3rd longwall at a depth of about 26 m. Here the seam consists of 3 benches, separated from one another by partings of barren rock 0.15 and 0.10 m thick. The first (upper)

the band has a thickness of 0.2 m and is separated from the second by an interbed of dark-gray, strongly sandy argillite. The second band, 0.48 m thick, is separated from the third by an interbed of light-gray, banded, strongly sandy argillite. The thickness of the third band reaches 0.33 m. The total thickness of the seam is 1.26 m, of which 1.0 m is coal and 0.26 m is mineral interbeds. In addition to the two interbeds separating the bands, thin sandy-clayey bands are developed in the seam and occur in all the bands. The roof and floor of the seam are dark-gray sandy argillite.

Petrographic section of the “Dvukharshinny” seam.

Legend:

• Vitrain.
• Lustrous coal, variety I.
• Lustrous coal, variety II.
• Dull coal, variety I.
• Dull coal, variety II.
• Fusain.
• Argillite.

Scale: 1 cm = 2 centimeters.

Fig. 27.

Coal could be divided macroscopically into four kinds: two bright and two dull. In addition, vitrite and fibrous coal were separately distinguished from the composition of the coal, insofar as the thickness of the lenses permitted this. The content and character of the distribution of the kinds of coal in the seam and in its individual packs are given in Table No. 13 below and in the petrographic section of the seam (Fig. 27). The total content of the kinds of bright and, separately, dull coal is indicated in the description of the groups. The content of vitrite and fusite is given in the same Table No. 13, but, since only the largest lenses of both kinds of coal were taken into account, their macroscopic percentage content is very approximate.

Table No. 13.

Macroscopic composition of coal from the Dvukh-Arshinny seam of the Chernogorsk deposit.

Main groups of coals	Name of macroscopic ingredients	Probable nature of ingredients	I pack: thickness of ingredients, cm	I pack: % of pack thickness	II pack: thickness of ingredients, cm	II pack: % of pack thickness	III pack: thickness of ingredients, cm	III pack: % of pack thickness	By seam: thickness of ingredients, cm	By seam: % of total workable seam thickness
Bright coals	Bright coal, kind I . . . .	Clarito-durite	—	—	1.8	4.0	9.7	29.0	11.5	11.0
Bright coals	Bright coal, kind II . . . .	Durito-clarite	12.2	61.0	32.3	67.0	12.1	36.0	56.6	56.0
Dull coals	Dull coal, kind I . . . .	Durite	6.3	31.0	6.1	13.0	6.0	18.0	18.4	18.0
Dull coals	Dull coal, kind II . . . .	Durite	1.1	6.0	3.4	7.0	3.7	11.0	8.2	8.0
	Vitrite coal . . .	Vitrite	0.2	1.0	2.2	4.0	1.3	4.0	3.7	4.0
	Fibrous coal . . .	Fusite	—	—	1.3	3.0	—	—	1.3	1.0
	Barren rock . . . .	Predominantly gray clayey sandstone	0.2	1.0	0.9	2.0	0.5	1.0	1.6	2.0
	Total . . .		20.0	100	48.0	100	33.3	100	101.3	100

I. Group of bright coals.

This group, as already noted above, includes two kinds of bright coal. Together the two kinds make up as much as 67.0% of the workable thickness of the seam, and by packs their total content is expressed in the following percentages: in the first pack—61%, in the second—71%, and in the third—65%.

The most bright coal in the group, coal of kind I, consists of a fine alternation of principal resin-bright bands with narrow and less numerous bands of brightly lustrous and dull coal. The general luster of the coal is resinous, rather strong, and more or less homogeneous. The color is black. The fracture is coarse and uneven. The coal appears dense and fairly hard. On surfaces parallel to the bedding, a considerable number of small films of soft and hard fusite are noticeable.

Bright coal of kind II differs very little from the preceding one. It contains somewhat more dull bands and therefore seems less—

less lustrous. As regards fracture, density, and color, these are here of approximately the same order as in the lustrous coal of variety I.

II. Group of dull coals.

The two varieties of dull coal combined in this group together make up as much as 26.0% of the total useful thickness of the seam. In individual benches the content of these varieties ranges from 37.0% in the first and 29.0% in the third to 20.0% in the second. The greatest role in the group belongs to dull coal of variety I; its content in the seam reaches 18.0%, whereas the content of dull coal of variety II is only 8.0%.

Dull coal of variety I has a faint resinous luster approaching dull-fatty, a grayish-black color, and a banded texture. The banding is weakly manifested and is expressed by an alternation of the principal dull bands with narrow and few bands of bright-lustrous coal. The fracture of the coal is uneven and fine. The coal is dense and hard. It contains much fusite, the inclusions of the latter usually being of very small size. Fusite, as always, is best detected on the bedding surfaces and is represented in the coal by both varieties.

Dull coal of variety II has a faint dull-fatty luster, a dark-gray color, a fine uneven fracture, and a weakly expressed banded texture. The impression of banding in the coal is created by small lenses of fusite and vitrite, which, being of very small size, are poorly noticeable; because of this, at first glance the coal seems almost homogeneous. Inclusions of fusite, being relatively few in number along planes perpendicular to bedding, are observed in very large quantity in planes parallel to it, and usually belong to the hard variety.

The large bands of vitrite and fusite singled out separately in the macroscopic study of the seam differ in no way (except size) from the smaller lenses of the one and the other coal that make up each of the varieties.

Mineral inclusions of secondary origin are represented in the coal only by films of gypsum and sulfides. They occur along parting planes, mainly in the lustrous coals, and almost always in direct association with one another (films of gypsum are filled with films of sulfides). These inclusions also occur along slickenside planes, which are sometimes observed in the coal.

Specific gravities and technical properties of the coals.

The specific gravities of the coal, according to Table No. 14, retain approximately the same dependence on luster as in the other seams: the most lustrous coals, which here are the coals of group I, give the lowest specific gravities (1.21), and, conversely, the dullest coal of variety II of group II gives the greatest specific gravity (1.27).

Table No. 14.

Specific gravities of lustrous and dull coals from the Dvukharshinnoye seam.

No.	Name of coal	Number of determinations	Extreme values of specific gravities	Mean values of specific gravities
1	Lustrous coal of variety I	15	1.21–1.23	1.22
2	Lustrous coal of variety II	15	1.20–1.23	1.22
3	Dull coal of variety I	10	1.23–1.27	1.24
4	Dull coal of variety II	10	1.23–1.30	1.27

Bright coals, as can be seen from the table, have almost identical specific gravities, which moreover differ among them only by very small fluctuations. This serves as confirmation of the correctness of the macroscopic separation of bright coals, and also characterizes their considerable homogeneity.

Dull coals, macroscopically likewise homogeneous in composition, in contrast to bright coals, show comparatively strong fluctuations in specific gravity. The explanation of such a phenomenon must be sought partly in the high content of fusite in these coals, and partly in the presence in them (especially in dull coal of rank II) of mineral inclusions, distributed in the mass of the coal in a generally uneven manner.

The data of the proximate analysis of the coals, given in Table 15, show that the coals of the Dvukharshinnyi seam are characterized by a weak caking capacity, decreasing from bright to dull coals.

Table No. 15.

Results of proximate analyses of coal from the Dvukharshinnyi seam

No.	Name of coal	Wл	Aл	Aс	Vл	Vг	Kл	Kг	Characterization of coke buttons
1	Vitrite coal. Bright coal of rank I, band 3	4,41	0,71	0,74	31,23	32,92	64,36	67,08	Weakly caking, unfused, black
2	Vitrite coal. Bright coal of rank I, band 3	4,16	1,39	1,45	40,36	42,72	55,48	67,22	Caking, slightly fused, gray in color
3	Bright coal of rank I, band 3	4,19	0,87	0,91	40,66	42,83	55,15	57,17	Slightly fused, gray in color, entirely unswollen
4	Bright coal of rank I, band No. 3	4,04	2,18	2,27	38,56	41,12	57,40	58,88	”
5	Bright coal of rank II, band 1	4,32	1,50	1,57	36,72	38,99	59,96	61,01	Weakly caking, black
6	Bright coal of rank II, band 3	3,97	2,06	2,14	38,54	41,01	57,49	58,99	Weakly caking, grayish-black.
7	Bright coal of rank II, band 1	3,69	1,82	1,89	33,81	35,78	62,50	64,22	Very weakly caking, black.
8	Dull coal of rank I, band 2	3,61	2,91	3,02	38,24	40,91	58,15	59,09	Weakly caking, black.
9	Dull coal of rank I, band 3	3,12	36,64	37,82	17,30	20,67	79,58	79,33	Non-caking.
10	Dull coal of rank II, band 2	3,69	1,74	1,81	32,03	33,88	64,28	66,12	Non-caking.
11	Dull coal of rank II, band 3	3,87	2,57	2,67	23,61	25,23	72,52	74,77	Non-caking.
12	Hard fusite (from the whole seam sample)	1,72	5,66	5,86	19,06	20,58	79,14	79,42	Non-caking.

Note: The characterization of the coke buttons was given by Prof. I. V. Gebler.

At the same time, in the general character of the petrographic composition of the coal, the reasons for its weak caking are evidently the same factors that were indicated above for other seams of the Chernogorsk deposit.

Izykhskoe Deposit

During the autumn of 1931 and the winter of 1931–1932, the Coal Exploration Administration of Kuzbassugol carried out the sinking of a deep exploratory shaft in the area of the former Izykhskoe coal mine. By the shaft were ...

four coal seams were exposed. The first (upper) seam, 0.5 m thick, was intersected by a prospecting pit at a depth of 12.6 m; the second seam, Metrovyi, 1 m thick—at a depth of 17.65; the third, called Sbrosovyi, 1.78 m thick—at a depth of 25.3 m; finally, the fourth, Nikol’skii seam, 2.46 m thick—at a depth of 57.1 m (Fig. 28).

Of the four seams cut by the prospecting pit, only two were sampled by us—the third and the fourth, as the thickest seams and those lying deepest below the ground surface.

V. The Sbrosovyi Seam.

1. MACROSCOPIC DESCRIPTION

The Sbrosovyi seam consists of three coal bands. The first (upper) band is separated from the second by an interbed of light-gray fine-grained sandstone 0.11 m thick and yields 0.55 m of coal. The second band is separated from the third by the same kind of interbed, 0.22 m thick, and has a thickness of 0.87 m. The thickness of the lower band is 0.33 m. The useful thickness of the entire seam is 1.75 m.

In the seam, macroscopically, we distinguished five kinds of coal—two bright and three dull coals.

Fig. 28.

Group of bright coals.

The total content of these coals in the seam reaches 52.0% of its thickness, and by bands it fluctuates from 54.0% in the first and 53.0% in the second bands to 42% in the third (Table 16). The content of each of the kinds separately fluctuates still more by bands. Thus, the first kind of bright coal in the first band constitutes 40.0% of its entire thickness, in the second—19.0%, and in the third—barely 4.0%. Significant fluctuations by bands are also observed in the content of the second kind of bright coal, but with the difference that the decrease in its role in the composition of the seam proceeds not from the upper band to the lower, but, on the contrary—from 38.0% in the third and 34.0% in the second to 14.0% in the first band.

The first kind of bright coal should be characterized as the brightest coal in the seam. The luster of the coal is resinous, but not sufficiently uniform, which is explained by the heterogeneity of the coal mass. The texture is weakly banded; it is expressed by the alternation of broader bright bands, which make up the principal clarite-durite mass, with a few small lenses of strongly bright coal (vitrain) and thin, likewise few, bands of dull (durite) coal. The fracture of the coal is from medium to coarse, more rarely fine, uneven, sometimes flat-conchoidal. The coal is black in color, is distinguished by considerable strength and by a very small number of cleavage cracks. According to the indicated physical properties, this kind may be assigned to clarite-durite coals. In the seam it forms interlayers of small thickness (from 0.1 cm to 3 cm), alternating with interlayers of other coals or barren rocks.

The distribution of the different coals in the vertical section of the Dafo seam is shown in Fig. 29.

Bright coal of the second variety has a considerably weaker and more heterogeneous luster and a more clearly expressed banded texture.

Petrographic section of the seam of the Sbrosovyi Izykh mine

Legend

• Bright coal
• variety I
• variety II
• Matte coal
• variety I
• variety II
• variety III
• Aremnyak

Scale: 1 cm = 2 centimeters.

Fig. 29.

In its general mass this coal is grayish-black in color, strong, little broken by cleavage cracks, and has a fairly coarse and somewhat more even fracture than that of the first type. As in the first type, the coal is composed of strongly lustrous bands of vitrite, less lustrous bands of clarito-durite, and dull bands of durite coal. But whereas in coal of the first type the lustrous bands of clarito-durite coal play the dominant role, in the present type the most essential role belongs to the dull bands of durite. The vitrite content is sharply reduced. This coal, as in the Gigant seam, may be called durito-claritic.

It is developed in the seam in the form of interbeds from 0.2 to 5.5 cm thick and is confined mainly to the II and III benches (Fig. 29).

Group of dull coals.

This group includes three types of coal that differ in luster, composition, fracture, and degree of mineralization. In the composition of the seam the group takes a somewhat smaller part than the group of lustrous coals and accounts in all for 47.0% of its total thickness. By individual benches the dull coals are distributed as follows: in the first bench they compose 44.0% of its thickness, in the second—45%, and in the third—56.0%. The content, by benches, of the individual types of these coals fluctuates very sharply. Thus, for example, dull coal of the III type, composing 1.0% of the thickness of the first bench and 2.0% of the second, is entirely absent in the third bench. Meanwhile, dull coal of the II type gives, in the first and second benches, respectively, 17.0 and 20.0%, and in the third bench—10.0%. Dull coal of the I type composes 25.5% of the first and 23% of the second bench, while in the third it gives almost half of its thickness—45.0%. Thus, the duller types (II and III) chiefly enrich the upper benches of the seam; dull coal of the I type, on the contrary, is most strongly distributed in the lower part of the seam.

All three types of dull coal form interbeds of small thickness in the seam (0.5–2, maximum 2.8–6.4 cm), alternating with one another, as well as with interbeds of lustrous coals and barren rocks. In thinner interbeds the dull coals are observed chiefly in the upper bench, where their thickness usually varies within limits up to 1.0 cm.

Dull coal of the I type has a very weak, uneven luster and a banded texture, expressed by the alternation of coarser dull bands of durite with very fine and sparse lustrous bands of clarite and vitrite. The color of the coal is dark gray. The fracture is uneven, splintery, from medium to coarse. The coal is strong and almost bears no cleavage cracks. The decisive predominance in it of gray dull bands of durite accounts for its gray color and uneven weak luster, and also permits this coal to be called banded durite.

The second type of dull coal is characterized by homogeneous composition, a dull greasy luster, and a fairly even coarse fracture. The coal is dark gray in color, very strong, contains no cleavage cracks, and is a typical durite coal.

The third type. The coal is massive, durite, of fine-grained texture; it has a dark gray color with a slight brownish tint and a very weak, uneven, granular-looking luster. Such luster is probably the result of the presence in the coal of barely macroscopically visible lustrous lenses of vitrite. The coal is strong, not broken by cleavage cracks, and has an uneven, slightly splintery fracture. Some of its interbeds in the seam are strongly enriched with films of pyrite, which are especially readily arranged in the coal along bedding surfaces.

Both groups of coals together constitute 98.0% of the total thickness of the seam; the remaining 2.0% consists of thin interbeds of barren rocks.

Vitrain and fusain could not be counted separately macroscopically, owing to the extremely small size of their lenses and bands, which very often have a thickness of less than 0.2 mm. In addition, the small lenses of fusain here are very difficult to distinguish macroscopically from the dull durite mass enclosing them. The latter is explained by the fact that fusain in this seam is usually hard and has the gray color and almost dull luster characteristic of hard fusain. Both of these features make the small lenses of fusain difficult to distinguish from bands of dull durite coal.

Fusain in the coals of the Sbrosovyi seam is more readily distinguished on bedding surfaces, where it appears as usually small films with a slightly noticeable silky luster. Sometimes these almost dull films have a brownish color and in such cases correspond to inclusions of mineralized fusain.

Interlayers and small lenses of mineral formations in most cases consist of grayish fine-grained sandstone, often in a fine mixture with coal matter. They are few in number, mostly have a small thickness (from 0.2 to 1.4 cm), and are distributed in the seam more or less uniformly through its entire thickness (Fig. 29). Among mineral inclusions of secondary origin, only pyrite and calcite are observed in the seam.

Pyrite is developed as small films of oval form, predominantly along bedding surfaces. It is most often encountered in dull coals of groups III and somewhat more rarely of group II. The macroscopic content of this mineral is approximately the same as in the Gigant seam.

Calcite is observed almost exclusively in the second variety of bright coal, in the form of small isolated films.

The data on the macrocomposition of the coals of the Sbrosovyi seam are summarized in Table 16. It should also be noted that the coal in the upper part of the seam bears clear signs of strong weathering: it is broken into separate small fragments, covered with brownish coatings, and has very low strength. The thickness of this strongly weathered part of the seam is 9 cm, or 16.0% of the thickness of the first bench and 5.0% of the thickness of the entire seam. Below, approximately to a depth of 26 cm from the roof of the seam, weathering is less pronounced. However—

Table No. 16

Macroscopic composition of the coal of the Sbrosovyi seam

Basic groups of coals	Coal varieties	Probable nature of the coals	I bench: test-pit No.	I bench: thickness of coal variety in individual test pits, cm	I bench: total, cm	I bench: % by bench	II bench: test-pit No.	II bench: thickness of coal variety in individual test pits, cm	II bench: total, cm	II bench: % by bench	III bench: test-pit No.	III bench: thickness of coal variety in individual test pits, cm	III bench: total, cm	III bench: % by bench	Total in seam, cm	Average % by seam
Bright coals	I variety	Clarito-durite coal	2	1.6	22.0	40.0	8	2.7	16.9	19.0	17	—	1.2	4.0	4.0	23.0
Bright coals	I variety	Clarito-durite coal	3	2.2	22.0	40.0	9	1.0	16.9	19.0	18	—	1.2	4.0	4.0	23.0
Bright coals	I variety	Clarito-durite coal	4	7.0	22.0	40.0	10	3.1	16.9	19.0	19	—	1.2	4.0	4.0	23.0
Bright coals	I variety	Clarito-durite coal	5	8.6	22.0	40.0	11	2.0	16.9	19.0	20	0.3	1.2	4.0	4.0	23.0
Bright coals	I variety	Clarito-durite coal	6	2.5	22.0	40.0	12	0.4	16.9	19.0	21	0.9	1.2	4.0	4.0	23.0
Bright coals	I variety	Clarito-durite coal			22.0	40.0	13	1.0	16.9	19.0			1.2	4.0	4.0	23.0
Bright coals	I variety	Clarito-durite coal			22.0	40.0	14	1.4	16.9	19.0			1.2	4.0	4.0	23.0
Bright coals	I variety	Clarito-durite coal			22.0	40.0	15	2.3	16.9	19.0			1.2	4.0	4.0	23.0
Bright coals	I variety	Clarito-durite coal			22.0	40.0	16	3.0	16.9	19.0			1.2	4.0	4.0	23.0

Continuation of the table on the following page.

Main group of coals	Coal types	Probable nature of the rock	I pack: seam no.	I pack: thickness of coal in individual seams, cm	I pack: sum, cm	I pack: %	II pack: seam no.	II pack: thickness of coal in individual seams, cm	II pack: sum, cm	II pack: %	III pack: seam no.	III pack: thickness of coal in individual seams, cm	III pack: sum, cm	III pack: % by pack	Total thickness, cm	Average % by seam
Shiny coals	II type	Durito-clarite coal	2	4.2	7.7	14.0	8	2.2	30.0	34.0	17	1.8	12.7	38.0	50.4	29.0
Shiny coals	II type	Durito-clarite coal	3	1.5	7.7	14.0	9	3.4	30.0	34.0	18	2.6	12.7	38.0	50.4	29.0
Shiny coals	II type	Durito-clarite coal	4	—	7.7	14.0	10	—	30.0	34.0	19	2.3	12.7	38.0	50.4	29.0
Shiny coals	II type	Durito-clarite coal	5	0.4	7.7	14.0	11	6.4	30.0	34.0	20	3.5	12.7	38.0	50.4	29.0
Shiny coals	II type	Durito-clarite coal	6	0.6	7.7	14.0	12	8.2	30.0	34.0	21	2.5	12.7	38.0	50.4	29.0
Shiny coals	II type	Durito-clarite coal					13	0.8	30.0	34.0
Shiny coals	II type	Durito-clarite coal					14	7.4	30.0	34.0
Shiny coals	II type	Durito-clarite coal					15	1.0	30.0	34.0
Shiny coals	II type	Durito-clarite coal					16	1.0	30.0	34.0
Clayey	I type	Durite coal	2	2.7	14.0	25.0	8	3.6	20.5	24.0	17	1.8	15.0	45.0	49.5	28.0
Clayey	I type	Durite coal	3	0.9	14.0	25.0	9	5.2	20.5	24.0	18	6.1	15.0	45.0	49.5	28.0
Clayey	I type	Durite coal	4	2.7	14.0	25.0	10	3.3	20.5	24.0	19	4.8	15.0	45.0	49.5	28.0
Clayey	I type	Durite coal	5	3.0	14.0	25.0	11	1.7	20.5	24.0	20	1.4	15.0	45.0	49.5	28.0
Clayey	I type	Durite coal	6	4.7	14.0	25.0	12	1.5	20.5	24.0	21	0.9	15.0	45.0	49.5	28.0
Clayey	I type	Durite coal					13	1.4	20.5	24.0
Clayey	I type	Durite coal					14	3.0	20.5	24.0
Clayey	I type	Durite coal					15	0.8	20.5	24.0
Clayey	I type	Durite coal					16	—	20.5	24.0
Matte coals	II type	Durite coal	2	—	9.4	17.0	8	4.3	17.2	20.0	17	—	3.5	10.0	30.1	17.0
Matte coals	II type	Durite coal	3	1.3	9.4	17.0	9	2.9	17.2	20.0	18	2.5	3.5	10.0	30.1	17.0
Matte coals	II type	Durite coal	4	2.3	9.4	17.0	10	—	17.2	20.0	19	—	3.5	10.0	30.1	17.0
Matte coals	II type	Durite coal	5	3.8	9.4	17.0	11	3.0	17.2	20.0	20	—	3.5	10.0	30.1	17.0
Matte coals	II type	Durite coal	6	2.0	9.4	17.0	12	6.4	17.2	20.0	21	1.0	3.5	10.0	30.1	17.0
Matte coals	II type	Durite coal					13	—	17.2	20.0
Matte coals	II type	Durite coal					14	—	17.2	20.0
Matte coals	II type	Durite coal					15	0.6	17.2	20.0
Matte coals	II type	Durite coal					16	—	17.2	20.0
Matte coals	III type	Durite coal	2	0.6	0.6	1.0	8	—	1.6	2.0	17	—	—	—	2.2	1.0
Matte coals	III type	Durite coal	3	—	0.6	1.0	9	—	1.6	2.0	18	—	—	—	2.2	1.0
Matte coals	III type	Durite coal	4	—	0.6	1.0	10	—	1.6	2.0	19	—	—	—	2.2	1.0
Matte coals	III type	Durite coal	5	—	0.6	1.0	11	—	1.6	2.0	20	—	—	—	2.2	1.0
Matte coals	III type	Durite coal	6	—	0.6	1.0	12	1.6	1.6	2.0	21	—	—	—	2.2	1.0
Matte coals	III type	Durite coal					13	—	1.6	2.0
Matte coals	III type	Durite coal					14	—	1.6	2.0
Matte coals	III type	Durite coal					15	—	1.6	2.0
Matte coals	III type	Durite coal					16	—	1.6	2.0
Barren rock	Barren rock	Sandy argillite	1	roof	1.4	3.0	7	Interbeds, 11 cm, separating packs 1 and 2	31.2	1.0	17	2.5-cm interbed separating seams 2 and 3	0.7	2.0	3.3	2.0
Barren rock	Barren rock	Sandy argillite	2	—	1.4	3.0	8	Interbeds, 11 cm, separating packs 1 and 2	31.2	1.0	18	—	0.7	2.0	3.3	2.0
Barren rock	Barren rock	Sandy argillite	3	—	1.4	3.0	9	Interbeds, 11 cm, separating packs 1 and 2	31.2	1.0	19	—	0.7	2.0	3.3	2.0
Barren rock	Barren rock	Sandy argillite	4	1.4	1.4	3.0	10	1.0	31.2	1.0	20	0.7	0.7	2.0	3.3	2.0
Barren rock	Barren rock	Sandy argillite	5	—	1.4	3.0	11	—	31.2	1.0	21	—	0.7	2.0	3.3	2.0
Barren rock	Barren rock	Sandy argillite	6	—	1.4	3.0	12	—	31.2	1.0	22	soil	0.7	2.0	3.3	2.0
Barren rock	Barren rock	Sandy argillite					13	0.2	31.2	1.0
Barren rock	Barren rock	Sandy argillite					14	—	31.2	1.0
Barren rock	Barren rock	Sandy argillite					15	—	31.2	1.0
Barren rock	Barren rock	Sandy argillite					16	—	31.2	1.0
									87.4				33.1		175.5

and here it is evident. This is indicated by the numerous and sharply expressed cleavage cracks cutting the coal in two directions, perpendicular and at an angle (50–60°) to the bedding, by dull tarnish colors along the cleavage planes, and by the relatively low strength of the coal. The thickness of this part of the seam reaches 17 cm and constitutes 31.0% of the total thickness of the first band.

No signs of tectonic disturbances are observed in the seam, apart from rare slickenside surfaces.

2. MICROSCOPIC DESCRIPTION.

Group of bright coals.

Bright coal of the 1st type under the microscope gives 75% durite, 14.0% clarite, 10.0% vitrite, and only 1.0% of other ingredients occupying an independent position in the coal.

Durite is distinguished by a very small content of formed inclusions. The main structureless mass accounts for 66.0% out of 75.0%, and only 9.0% for various formed structures. The main mass of the durite is of the ordinary type, structureless, light gray in color, and not fissured. The formed inclusions are rather varied. The most numerous among them are small fragments of cuticle and small grayish-brown fragments, partly remaining indeterminate, partly assigned to spores¹.

The next place, by percentage content in the durite, is occupied by grayish-brown formations of irregular shape, distinguished by considerable size. As in the Gigant seam, we assign them to algae. After them come more or less considerable accumulations of light-gray oval, possibly resinous, bodies. Less developed in the durite are yellowish-white spores and their fragments, as well as cuticles preserved unruptured and small fragments of xylitic and fusitic tissues.

Many areas in the durite, and even entire bands rich in structureless mass, are characterized by a considerable content of resinous bodies, large fragments of cuticle, and a comparatively very low content of other formed elements. Such areas and bands in the durite, as in the Gigant seam, we distinguish under the name clarito-duritic. The presence of such areas in the durite indicates its complex composition and close connection with clarite.

The quantitative ratio of the structureless mass and formed elements in the durite, as well as the qualitative composition of the latter in the Sbrosovyi seam, bring it close to the durite of the bright coal of the 1st type of the Gigant seam.

Clarite is typical for Minusinsk coals. It consists of a main light-gray structureless mass and of thin and medium-thickness cuticles immersed in it, accumulations of light-gray oval bodies, and very few (almost isolated) inclusions of formed elements of durite. Clarite occurs predominantly in the form of narrow lenses and interlayers alternating with bands of durite and clarito-durite.

Vitrite is also typical: structureless in appearance, light gray in color, contains no inclusions, and is characterized by considerable fissuring. It is observed in polished sections as lenses and interlayers, sometimes having an irregular curved form and an orientation not parallel to the bedding. Their thickness is usually small and only in individual cases reaches up to 0.9 mm.

Among the other independent ingredients, which together constitute

1.00% of the total thickness of coal of this variety were assigned: xylite formations of type I and mineral inclusions of indeterminate origin.

The inclusions of xylite of type I, as in the Gigant seam, have a yellowish-white and, more rarely, gray color, and a coarse-, medium-, and fine-cellular structure. From the fragments of xylite of type I recorded in the composition of durite, they differ only in their larger dimensions.

The mineral inclusions are characterized in the polished section by very strong relief, indicating their considerable hardness. They have an oval, more rarely angular form and a dark-gray or yellowish-white coloration. The yellowish-white inclusions, moreover, display a rather strong luster.

The described composition of coal of variety I gives grounds for assigning it, as in the Gigant seam, to the category of clarito-duritic coals.

Bright coal of variety II differs from coal of variety I by a higher content of durite, xylite, and fusite, and at the same time by a sharply reduced content of vitrite and clarite. The content of mineral inclusions remains almost unchanged.

Durite is somewhat more saturated with structured elements (12.0% as against 9.0% in variety I). The main mass and the structural formations in the durite remain the same as in the durite of the preceding coal. Here only the quantitative ratio in the composition of the structured formations changes, namely: the content of small fragments of fusitic and especially xylitic cells, spores and their coats, fragments of cuticle, and lilac-gray fragments rises sharply; at the same time the content of the lilac-gray alga, light-gray oval bodies, and preserved cuticles noticeably decreases. Areas of clarito-durite are few in number.

The clarite of this variety under the microscope remains completely identical with the clarite of bright coal of variety I and differs only in occupying here a substantially smaller volume. It is observed as lenticular areas, more rarely as narrow interlayers, amid the duritic field. Vitrite is developed as small and narrow lenses, sometimes as broader interlayers. Xylite of types I and II is observed in the form of small and narrow lenses and fragments of yellowish-white, partly grayish, coloration. Inclusions of xylite of type I decidedly predominate.

Fusite is distributed in the coal as small lenses, more often as fragments of coarse- and medium-cellular structure. Fine-cellular and thin-walled tissue was encountered here very little. The coloration of the fusitic formations, like that of the xylitic ones, is yellowish-white, more rarely grayish. The tissue is more or less preserved and is not filled with mineral matter. In view of the fact that, in the composition of this coal, after durite the most substantial part is taken by clarite, this coal should be called durito-claritic.

The data on the microcomposition of the coals of the Sbrosovyi seam are summarized in Table 17.

Group of dull coals

Dull coal of variety I is composed essentially of durite, considerably richer in structured elements than in the group of bright coals (Table 17). Along with this, in it the content of mineral inclusions and of larger areas of fusitic and xylitic tissue noticeably increases. At the same time, the content of clarite and of the basic structureless mass of durite is substantially reduced in the coal, with a more or less stable content of vitrite. Such a change in the quantitative ratios of the ingredients naturally affects, above all, the weakening of the luster of the coal.

Durite, saturated with structured elements, displays a still somewhat greater variety in spores and small indeterminate inclusions. Whereas in the durites of bright coals the most substantial

Table No. 17

Microscopic composition of coal from the Sbrosovy seam, %

Main groups and coal ranks by macroanalysis	By class	By nature	Coal type designation	Main structureless mass	Spores	Cuticles	Algae	Algae and their fragments	Fine cuticle fragments, spores, fine fusite and xylite fragments, cellular and resinous organic formations, pyroxylitic formations	Total shaped constituents in durite	Total durite	Spores	Cuticles	Total clarite	Vitrite	Xylite, type II	Xylite, type I	Total xylite	Fusite	Concretions of iron oxides	Sulfides	Other mineral inclusions	Total mineral inclusions	Total of enumerated components
Bright coals	Clarito-durites	Clarito-duritic	I type	66.0	traces %	1.0	1.0	6.0	9.0	75.0	10.0	4.0	traces %	14.0	2.0	—	6.0	traces %	—	traces %	—	—	traces %	100
Bright coals	Clarito-durites	Clarito-duritic	II type	71.0	1.0	traces %	traces %	10.6	12.0	83.0	4.0	2.0	traces %	6.0	2.0	1.0	6.0	7.0	2.0	—	—	traces %	traces %	100
Matte coals	Durites	Duritic	I type	67.0	1.0	1.0	traces %	16.0	18.0	85.0	1.0	traces %	—	1.0	2.0	—	6.0	7.0	3.0	—	—	1.0	1.0	100
Matte coals	Durites	Duritic	II type	55.0	2.0	traces %	—	28.0	32.0	87.0	—	—	—	—	1.0	1.0	8.0	9.0	2.0	—	—	traces %	traces %	100
Matte coals	Durites	Duritic	III type	43.0	1.0	traces %	—	42.0	46.0	89.0	—	—	—	—	2.0	2.0	5.0	7.0	1.0	—	0.3	1.3	1.0	100

role among the formed elements belongs to small fragments of cuticles, lilac-gray formations, and algae, while only a very insignificant role is played by spores and small fragments of fusite and xylite cellular tissue; in the durite of this coal, on the contrary, the primary role among the formed elements belongs to spores and small fragments of fusite and xylite; fragments of cuticles and lilac-gray formations play a subordinate role in it. Algae, preserved cuticles, and especially light-gray oval bodies are rarely observed here.

Such a petrographic composition of the durite distinguishes it from the durites of lustrous coals and brings it closer to the type of spore durites.

Clarite and vitrite take only a very small part in the composition of this coal (1 and 2%). Both are observed as small lenses and bands, as well as irregularly shaped areas within the durite.

Xylite of types I and II, in contrast to clarite and vitrite, plays a more substantial role (up to 7%). It usually occurs as small fragments and lenses of yellowish and, more rarely, grayish coloration. Sometimes xylite lenses reach a considerable thickness—up to 0.2 mm. More often, however, their thickness ranges from 0.07 to 0.03 mm. Type I xylite is the most widespread in the coal.

Fusite is represented in the coal by rather numerous lenses and fragments, in most cases of insignificant thickness (0.02–0.05 mm). Their color is yellowish or yellowish-gray; the structure is fine-, medium-, and coarse-cellular. The cellular tissue is predominantly thin-walled and usually free of mineral-mass infilling. Fusite of coarse-cellular structure, and also of grayish coloration, was encountered in very limited quantity.

Among the mineral inclusions in the coal there are very small and few grains of pyrite (less than 0.1%) and larger and more numerous dark-gray, probably quartz grains. The latter have an oval or irregularly angular form and high relief.

Dull coal, variety II differs microscopically from dull coal of variety I by: 1) a higher content of durite, and one considerably more saturated with formed particles; 2) a higher content of xylite; 3) a somewhat reduced content of vitrite, fusite, and mineral inclusions; and 4) the complete absence of clarite.

The sharply increased content of formed elements in the durite, up to 32% (Table 17), as well as the increased percentage of xylite (9.0%), explain the marked weakening of luster in this coal.

Durite, unlike the durite of dull coal of variety I, increases its structural part both at the expense of spores and small fragments of xylite and fusite, and at the expense of small lilac-gray fragments, algal remains, and small fragments of cuticles. Cuticles are very few here; light-gray oval bodies are completely absent.

Vitrite under the microscope gives a very small percentage (about 1.0%) and is observed in the form of small lenses of the appearance usual for this ingredient.

Xylite of types I and II is developed predominantly as short and thin (0.03–0.1 mm) lenses and fragments. The coloration of both is yellowish, more rarely yellowish-gray. Inclusions of type II xylite predominate.

Fusite, like xylite, is represented by small lenses and especially often by fragments of the same yellowish and yellowish-gray coloration. Their structure, with rare exceptions, is fine- and medium-cellular. The cellular tissue is for the most part thick-walled, more or less well preserved and usually not mineralized. The mineral mass filling some of the fusite formations has a dark-gray color, such as is observed in the mineral inclusions in the structureless mass of the durite.

Dull coal, variety III is characterized by a further increase—

Fig. 4.

Fig. 5.

Fig. 6.

Fig. 7.

differ considerably. While their physical properties are, in general, similar, they differ in the two seams in the character and degree of mineralization and, in connection with this, also in specific gravities. The latter, for the group of dull coals, which are distinguished by increasing mineralization—moreover of not only primary but also secondary character—is entirely natural.

Table No. 18.

Specific gravities of the macroscopic ingredients of coal from the Sbrosovyi seam.

No.	Name of ingredients	Quantity determined	Extreme values of specific gravities	Mean value of sp. gravities	Note
1	Bright coal, type I	25	1.18–1.26	1.21	—
2	Bright coal, type II	35	1.19–1.26	1.22	—
3	Dull coal, type I	40	1.17–1.34	1.25	—
4	Dull coal, type II	25	1.21–1.40	1.32	—
5	Dull coal, type III	10	1.38–1.49	1.43	—

Table 19 gives the data of the proximate analysis of coals from the Sbrosovyi seam. Along with the technological properties common to the coals of the Minusinsk Basin, this table shows a rather high caking capacity of the coal of the Sbrosovyi seam, compared with the Chernogorsk coals. It is evident from the table that the caking capacity of all types, both bright and dull coals of the Sbrosovyi seam of the Izykh deposit, is higher than the caking capacity of the same coals from the seams of the Chernogorsk deposit. In the Sbrosovyi seam a weak caking capacity is retained even in the group of dull coals. But the best caking is given by bright coal of type I. The coke buttons of this coal, according to the conclusion of Prof. I. V. Gebler, are very close to the coke buttons of normal coking coals. In bright coals of type II the caking capacity already weakens sharply. But a mixture of bright coals of types I and II in a ratio of 1:1 gives a button that is sufficiently strong, with a reduced degree of fusion. Average coal samples, both for individual benches and for the entire Sbrosovyi seam, showed weak caking.

On the question of the reasons for the increased caking capacity of the coal of the Sbrosovyi seam, the following observations may be made. The petrographic composition of this seam is, in general, very close to the composition of the coals of the Chernogorsk deposit. In the composition of the bright coals of types I and II of the Sbrosovyi seam, only a few elements can be indicated that are more favorable for caking than in the corresponding coals of the Chernogorsk deposit—for example, in the Gigant seam. Such are the reduced content of fusite to 0%–2% (in the Gigant, 1%–5%–7%) and an equally reduced content of xylite to 0%–7% (in the Gigant, 1%–10%–11%). One may also point to a somewhat more favorable composition of durite: in the Sbrosovyi seam the structureless mass of durite in bright coal of type I amounts to 66%, in the Gigant seam to 60%. But in the Gigant seam bright coal of type I has a higher percentage of clarite. The amount of vitrite in both is the same. In the bright coals of the Sbrosovyi seam, attention is also deserved by the higher content, in the clarite and in the structureless mass of durite, of vitrinitized cellular areas, although the latter, unfortunately, were not accurately accounted for volumetrically. All this compels us to suggest that the increased caking capacity of the coals of the Sbrosovyi seam is due not so much to its more favorable petrographic composition as to the general increase, in the Izykh deposit, in the degree of coalification.

Table 19

Technical analyses of coals from the Sbrodovo-Izykh deposit

No.	Sample description	\(W^a\)	\(A^a\)	\(V^\Gamma\)	\(K^\Gamma\)	\(V^{?}\)	\(K^{?}\)	Characteristics of the coke button	By whom the analyses were made
1	Lustrous coal, type I	5.04	7.06	44.96	55.04	39.52	55.44	Fused, with cracks, silvery.	Chemical laboratory of S.F.I.M. (Siberian branch of the Institute of Fossil Materials, NKTP S.).
2	Lustrous coal, type I	4.06	2.70	43.81	56.19	40.85	55.09	Fused, with cracks, silvery.	Chemical laboratory of S.F.I.M. (Siberian branch of the Institute of Fossil Materials, NKTP S.).
3	Lustrous coal, type I	4.14	7.02	47.06	52.94	41.81	54.05	Fused, with cracks, silvery.	Chemical laboratory of S.F.I.M. (Siberian branch of the Institute of Fossil Materials, NKTP S.).
4	Lustrous coal, type I, from bench 1	—	—	—	—	—	—	Caking, fused, dense, almost not swollen, fairly strong.	Chemical laboratory of S.Kh.T.I. (Siberian Chemical-Technological Institute).
5	Lustrous coal, type I, from bench 2	—	—	—	—	—	—	Caking, fused, dense, almost not swollen, fairly strong.	Chemical laboratory of S.Kh.T.I. (Siberian Chemical-Technological Institute).
6	Lustrous coal, type I, from bench 3	—	—	—	—	—	—	Parts fused, not swollen, dense, sufficiently strong crust.	Chemical laboratory of S.Kh.T.I. (Siberian Chemical-Technological Institute).
7	Lustrous coal, type II	3.16	4.41	44.97	55.03	41.57	55.27	Caking, with cracks.	Chemical laboratory of S.F.I.M. NKGS.
8	Lustrous coal, type II	6.96	14.26	43.67	56.33	34.41	58.63	Caking, with cracks.	Chemical laboratory of S.F.I.M. NKGS.
9	Lustrous coal, type II	4.72	6.08	45.35	54.65	40.46	44.82	Button fused, silvery.	Chemical laboratory of S.F.I.M. NKGS.
10	Matte coal, type I	5.16	2.77	40.76	59.24	37.52	57.32	Caking, very weakly fused, at the edges; black, not swollen.	Chemical laboratory of TsKhTI.
11	Matte coal, type I	3.86	12.35	45.13	54.87	37.82	58.92	Caking, with cracks.	Chemical laboratory of SFiMKa.

Technical analysis was not performed for coal from benches 1, 2, and 3; only the caking capacity of the coal was determined.

No.	Sample / horizon	1	2	3	4	5	6	Macroscopic description	Laboratory
12	Dull coal, angle of the 1st order	4.00	14.04	45.02	54.98	36.70	59.10	Sintered, with cracks.	Chemical Laboratory, SFIM
13	Dull coal, angle of the 1st order	4.45	4.67	40.15	59.85	36.49	59.06	Sintered, black, very weakly swollen.	SKhTI
14	Dull coal, angle of the 2nd order	4.30	21.43	48.67	51.33	36.15	59.55	Sintered, with cracks.	Chemical Laboratory, SFIM
15	Dull coal, angle of the 2nd order	3.80	18.13	44.60	55.40	34.82	61.38	Sintered, with cracks.	NKTP
16	Dull coal, angle of the 3rd order	3.54	34.04	49.85	50.15	31.12	65.34	Not sintered.	SFIM
17	Dull coal, angle of the 3rd order	4.71	9.83	45.33	54.64	38.76	56.53	Sintered; at the edges slightly fused, almost not swollen.	SKhTI
18	Mixture of bright coal of the 1st and 2nd orders in a ratio of 1:1	—	—	—	—	—	—	Only caking capacity was determined: partly fused, entirely not swollen, sufficiently strong.	SKhTI
19	Same	—	—	—	—	—	—	Only caking capacity was determined: sintered, weakly fused at the edges, dense, entirely not swollen, sufficiently strong.	SKhTI
20	Middle coal sample, by seam 1	—	—	—	—	40.70	59.30	Weakly sintered, black, almost not swollen.	SKhTI
21	Middle coal sample, by seam 2	—	—	—	—	42.04	57.96	Weakly sintered, black.	SKhTI
22	Middle coal sample, by seam 3	—	—	—	—	26.48	73.52	Caked together, black.	SKhTI
23	Average corner sample	3.96	11.57	45.33	54.67	38.29	57.75	Weakly sintered, black.	SKhTI
24	Mixture of coal from the 2nd and 3rd benches, in a proportion corresponding to the thickness of these benches	—	—	—	—	—	—	Only caking capacity was determined: caked together, black.	SKhTI

Note. Determination of coke buttons in the SFIM laboratory was carried out by the head of the laboratory, Maksimova. Determination of coke buttons obtained in the chemical laboratory of SKhTI was carried out by Prof. Geller.

It is very important to take into account, finally, the circumstance that the sample of the Sbrosovyi seam, as was already indicated above, was taken from a distinctly oxidized zone. Outside the zone of oxidation, i.e., at a depth of about 70 m and more, the coals of this seam, one should expect, will give still higher caking.

VI. Nikolsky Seam.

1. MACROSCOPIC DESCRIPTION.

The Nikolsky seam is stratigraphically the lowest of the four seams exposed in the area of the Izykh hard-coal deposit by an exploratory prospecting pit of the Kuzbassugol Coal Prospecting Administration in 1932.

Sampling of the coal for its petrographic study was carried out by the mining foreman of the Coal Prospecting Administration, Iovikov. According to the coal hand specimens submitted and the section of the seam appended to them, its total thickness at the sampling site is 2.45 m. At this place the seam consists of three benches (Fig. 30), separated by two interbeds of light-gray sandy argillite, which also forms the floor and roof of the seam.

The first (upper) bench is separated from the second by four interbeds of argillite and argillaceous sandstone, alternating with thin coal layers, and is the thickest in the seam (1.03 m). The second bench is separated from the third by an argillite layer 0.35 m thick and has a thickness equal to 0.55 m. The third bench is the smallest in the seam (0.30 m). In all benches, mineral clayey interbeds play a noticeable role. In benches I and II the content of these interbeds amounts to 6% of the corresponding bench thicknesses. In the third it decreases to 5%. Their thickness usually ranges from 0.5 to 2.5 cm.

In the macroscopic study, the coal of the seam was divided into four varieties: two bright and two dull. In addition, within the composition of the seam, mineralized coal with a total thickness of 0.08 m was also recorded separately.

Group of bright coals.

The total content of the group in the seam reaches 69% of its entire thickness. By benches it changes as follows: 66.0% in the first bench, 75% in the second, and 76% in the third. Sharper fluctuations by benches are observed in the content of each of the coal varieties separately. Thus, for example, bright coal of variety I in the first bench amounts to 29%, while in the second it gives 72% and in the third 66%. Bright coal of variety II, on the contrary, takes the greatest part in the composition of the first bench (37%). In the other benches its content decreases to 3% in the second and 10% in the third (see Table No. 20).

Bright coal of variety I plays the most substantial role in the seam: it gives, overall for the seam, up to 44% of its entire thickness (see Table No. 20). Its luster is resinous, rather strong. The color is black. On careful examination the coal proves to be heterogeneous in composition and consists of alternating rather broad bands of weakly bright coal, narrow bands of strongly bright vitrain, and a few, likewise very narrow (less than 0.3 cm), bands of dull coal. The coal cleaves comparatively easily along the bedding; on the surfaces thus obtained, numerous, though in most cases small, films of dull coal are sometimes clearly visible. The fracture perpendicular to the bedding is irregular, from medium to coarse. The coal has considerable strength and a very small number of cleavage cracks. These macroscopic features bring the coal close to bright coal of variety I from

Table No. 20

Macroscopic composition of coal from the Nikolsky seam

Main coal groups	Coal types	Probable nature of the coal	I bench: coal thickness in the bench, cm	I bench: % of bench thickness	II bench: coal thickness in the bench, cm	II bench: % of bench thickness	III bench: coal thickness in the bench, cm	III bench: % of bench thickness	Rock thickness in the seam, cm	% of seam thickness
Bright coals	Bright coal, type I	Clarito-duritic coal	37.0	29.0	35.8	72.0	18.3	67.0	91.0	45.0
Bright coals	Bright coal, type II	Durito-claritic coal	45.0	37.0	1.5	3.0	2.7	10.0	50.0	24.0
Dull coals	Dull coal, type I	Duritic coal	34.5	26.0	3.4	7.0	2.8	10.0	40.7	20.0
Dull coals	Dull coal, type II	Duritic coal	—	—	2.9	6.0	—	—	2.9	1.0
Mineralized coal	Mineralized coal	Coal in a fine mixture with sandy-clayey material	29.0	2.0	2.9	6.0	2.3	8.0	8.1	4.0
Waste rock	Waste rock	Predominantly gray sandy argillite	7.2	6.0	3.0	6.0	1.4	5.0	11.6	6.0
Total	Total	Total	127.1	100	49.5	100	27.5	100	204.1	100

of the Sbrosovyi seam and permit it to be classified as clarito-duritic coals. This coal is observed in the seam as interbeds predominantly 0.5–2 cm thick and, at most, 5.9–8.6 cm thick, with the thicker interbeds developed mainly in the second bench (see the petrographic section of the seam, Fig. 31).

Section of the Nikolsky seam of the Izikhsky deposit (according to Akademugol).

Conventional symbols

Symbol	Meaning
■	Coal
▥	Argillite
▦	Sandy argillite

Scale: 1 centimeter = 20 centimeters.

Fig. 30.

Lustrous coal of type II differs from coal of type I by a greater content of dull bands, which in this case also have somewhat larger dimensions (up to 0.5 mm in thickness). This circumstance has a substantial effect on the macroscopic properties of the coal: it appears less lustrous, less black, and less homogeneous in composition, with more clearly expressed banding. The coal is sufficiently strong, has almost no cleavage cracks, and, like the preceding type, splits easily along the bedding. The resulting surfaces are covered with numerous, often large films of dull coal, as well as with small films of fusite (more often hard). The fracture of the coal, perpendicular to the bedding, is uneven, irregular, from medium to coarse.

The coal occurs in the seam as interbeds from 0.1 to 3.9 cm thick. The most widespread are interbeds 0.5–1.5 cm thick (see the petrographic section of the seam, Fig. 31).

Group of dull coals.

This group includes two types of dull coal, differing from one another mainly in the character of their luster and in color. Their total content in the seam is considerably lower than that of the lustrous coals and amounts to only 21% of the seam thickness. The content of coals of this group by benches is very variable: in the first bench it equals 26.0%, in the second—13.0%, and in the third only—10.0% of their thickness. Thus we have a successive decrease in the role of dull coals from the upper bench to the lower. But the content of the individual types of dull coals by benches changes sharply and is devoid of any regularity (see Table No. 20). It can only be said that the most substantial role in the seam belongs to dull coal of type I.

Petrographic section of the Nikolsk seam

Legend:

• Bright coal, type I
• Bright coal, type II
• Dull coal, type I
• Dull coal, type II
• Clayey argillite
• Argillite

Scale: 1 cm = 2 centimeters

Fig. 31.

Matte coal of the first variety has a more or less massive texture, a dark-gray color, and an insufficiently uniform matte-resinous luster. Some heterogeneity in the luster is a consequence of the presence in the coal of small and not very numerous inclusions of brightly lustrous coal (probably vitrite). The coal is very hard, contains almost no parting cracks, has an irregular coarse fracture and, unlike the lustrous coals of group I, splits with difficulty along the bedding. The coal may be assigned to the type of durite coals. It occurs in the seam usually as narrow bands 0.3–0.5 cm thick. Very rarely their thickness reaches 8.1 cm.

Matte coal of the second variety has a brownish-black color and a coarse, fairly even fracture. The coal is hard, contains no parting cracks at all, but splits comparatively easily along the bedding, forming matte fracture surfaces with few and small films of lustrous (vitrite) coal on them.

At first glance this coal appears to be of homogeneous composition, but on more detailed study small lenses of vitrite, barely perceptible to the naked eye, are noticeable in it; although generally not numerous, they nevertheless somewhat disturb the uniformity of the coal’s luster. It should also be noted that when the coal is split along the bedding, thin leaves can be obtained which ignite without particular difficulty from the flame of a match, giving off a characteristic odor. This latter property compels one to regard this coal as close to combustible shale. It is observed in the middle part of the seam (in the second bench) in the form of one interlayer of small thickness (2.9 cm).

Mineralized coal is distinguished by its dark-gray color, matte luster, and almost massive texture (only with difficulty can extremely small lenses of lustrous coal be noticed). The fracture is uneven. The coal is hard, has a high specific gravity, easily perceptible even when weighed in the hand. The coal forms interlayers from 0.3 to 2.3 cm thick, always in direct contact with interlayers of barren rock, and evidently represents a fine mixture of coaly and clayey material.

Among mineral inclusions of secondary origin in the composition of the seam, only pyrite was observed, in the form of a few oval films or accumulations along the planes of parting.

2. MICRODESCRIPTION.

Group of lustrous coals.

Lustrous coal of the first variety consists, under the microscope, essentially of durite—62%, clarite—28%, and partly vitrite—8%; the remaining ingredients take an insignificant part in the composition of the variety. (Table 21).

Durite occurs here in the form of bands, sometimes broader and sometimes narrower, alternating with bands of clarite and, more rarely, vitrite. In most cases they are very weakly saturated with formed bodies, which is very characteristic of the durite of this variety. Of the total volume of durite in the coal, 88% is accounted for by the principal structureless mass, and only 12% by various formed bodies. However, this ratio is not constant for durite: while some bands of durite are rather strongly saturated with formed bodies, others prove to be almost free of them.

Among the formed inclusions in durite, the greatest role is played by fragments of spore coats, whole spores, small fragments of xylitic tissue, fragments of thin cuticle, and small lilac-gray formations of indeterminate origin (probably partly spores, similar to those noted in the Gigant seam and the Sbrosovyi seam). Other formed bodies are represented here in limited quantity. These include

Table No. 21

Microscopic composition of coals from the Nikol’skii seam (in percent).

Main coal groups by maceral composition	By luster	By nature	Coal name	Basic structure mass	Spores	Algae	Structural formations: small fragments, forms, cuticles and epidermis, spores, prosench., parench.	Total formed matter	Total durite	Composition in clarite: basic structure mass	Composition in clarite: small forms, fragments, cuticles, resin bodies	Total clarite	Vitrite	Xylite II type	Xylite I type	Total xylite	Fusite	Mineral inclusions: sulfides	Mineral inclusions: other mineral inclusions	Total	Inorganic content in the seam	Total	Simple content of the type in the seam
Lustrous coals	By luster	Claritic	Lustrous coal, type I	56.0	1.0	fractions of a %	5.0	6.0	62.2	25.0	3.0	28.0	8.0	fractions of a %	1.0	1.0	fractions of a %	—	fractions of a %	fractions of a %	fractions of a %	100	45.0
Lustrous coals	By luster	Durite-claritic	Lustrous coal, type II	75.0	2.0	fractions of a %	7.0	10.0	83.0	2.0	—	2.0	4.0	2.0	8.0	10.0	fractions of a %	—	fractions of a %	fractions of a %	fractions of a %	100	24.0
Dull coals	By nature	Duritic	Dull coal, type I	40.0	4.0	1.0	43.0	48.0	88.0	—	—	—	1.0	2.0	8.0	10.0	fractions of a %	—	fractions of a %	fractions of a %	fractions of a %	100	20.0
Dull coals	By nature	Duritic	Dull coal, type II	37.0	1.0	2.5	42.0	45.0	82.0	—	—	—	12.0	fractions of a %	fractions of a %	fractions of a %	—	fractions of a %	5.0	5.0	5.0	100	1.0

fragments of lilac-gray algae, fragments of large cuticles, fragments of fusite tissue, and very small inclusions of a yellowish-white color and irregular angular form. The latter are possibly fragments of individual thick-walled fusite cells. In addition, in durite bands containing few formed elements, light-gray resinous bodies and relatively well-preserved cuticles are often observed. Such bands represent, as it were, a gradual transition from durite to clarite and may be called clarite-durite. The presence of these bands in durite makes its composition complex and brings this durite close to the durites of the bright coals of type 1 of the Gigant and Sbrosovyi seams.

Clarite consists of a principal light-gray structureless mass and thin cuticles embedded in it, as well as accumulations of light-gray (as the principal mass) oval bodies, which we assign to resins. Sometimes, in clarite bands one can see isolated inclusions from among the formed structures of durite. In clarite, among the formed elements, the main role belongs to resinous bodies, which make up in it no less than \(2/3\) of the total content of the latter.

Vitrite is observed as narrow and predominantly short lenses of light-gray coloration. A feature of the vitrite of this coal is the extremely weakly expressed fissuring in its bands and lenses.

Xylite is represented almost exclusively by one type; it is observed in the form of small fragments with medium- and large-cellular structure. Very little fine-cellular xylite, as well as xylite in large lenses, has been noted. The coloration of xylitic structures is, as a rule, faintly yellowish and only in rare cases light-gray.

Fusite, like xylite, is observed mainly as small fragments with medium- and large-cellular structure, of pale-yellowish coloration; it is free from filling by mineral mass. The tissue is predominantly thick-walled and relatively well preserved. Fusite occurs very rarely as large fragments, and still more rarely as bands or lenses. Like xylite, it is almost always observed in durite bands strongly saturated with formed structures.

Algae, as in the seams described above, have a lilac-gray coloration, rarely a cellular structure, and an irregular elongated form. They are poorly developed here and usually occur as small and not numerous fragments in durite and clarite-durite.

The microscopic picture of the described coal type shows its clarite-durite nature, which confirms the similarity noted above between this coal and the bright coal of type 1 of the Sbrosovyi seam.

The microscope reveals in the coal a comparatively small content of formed structures (including fusite and xylite tissue) and a very high content of the principal structureless mass of durite and clarite. If all formed structures are combined into one group, and the principal mass of durite and clarite together with vitrite into another, it turns out that the first group accounts for approximately 11.0% of the total coal volume, and the second for 89.0%. The decisive predominance of the second group in the coal accounts for its fairly strong luster; and the presence in it of vitrite bands and durite bands rather strongly saturated with formed structures gives it its banded texture.

Bright coal of the second type differs from the first, on the one hand, by a higher content of durite and xylite (83% against 62% and 10% against 1.0%) and, on the other hand, by a reduced content of clarite (2%—28%) and vitrite (4%—8%). Owing to this, the total content of structural elements here increases noticeably (from 11% to 21%),

and the total content of vitrite and of the main mass of durite and clarite correspondingly decreases (from 89% to 81%).

Durite of this kind, in the degree of saturation with formed constituents, differs little from the durite of bright coal of type I. In it there is only a somewhat increased content of spores, fragments of spores, and small fragments of xylite tissue. As for the other formed elements, they remain here in approximately the same quantities and have the same petrographic composition as in the durite of bright coal of type I.

The distribution of formed constituents in the main mass of durite is uneven. Bands or areas of durite poor in them always contain more structureless mass, resin bodies, and preserved cuticles, which brings them very close to clarite. Such bands and areas in durite, by analogy with those encountered earlier in coals of type I, may be called clarite-duritic. They constitute a considerable part of the durite and probably provide the more or less satisfactory caking capacity observed in coal of this kind. The caking capacity need not be attributed to isolated bands of vitrite or clarite, since both have been ascertained here in limited quantity.

Under the microscope, clarite gives an ordinary-looking light-gray groundmass, in which numerous thin cuticles, resin bodies, and, as a rare exception, separate fragments of spores and pieces of xylite and fusite tissues are embedded.

Cuticles in thin sections are observed as more or less well preserved. They are almost always elongated along the bedding and usually have a mutually parallel orientation. Sometimes the cuticles are tightly compressed, as if intertwined with one another.

Resin bodies usually occur in accumulations elongated along the bedding. They are predominantly small in size, light gray in color, and oval, rarely cylindrical, in shape. Each of these bodies is bordered around the periphery by a thin brown rim, very similar to a cuticle.

Vitrite is light gray in color and structureless in appearance; it is observed as few and usually small lenses 0.04–0.07 mm thick. A distinctive feature of the vitrite of this coal is the extremely weak development of fissuring in it.

Xylite is predominantly of type I, with a pale yellowish and, as an exception, light-gray coloration. This ingredient occurs in the coal mainly as small but numerous fragments with a medium- and large-cellular structure. Xylite in large fragments, as well as with a fine-cellular structure, was observed in comparatively small amount.

Fusite, in terms of the volume it occupies in the coal, is far inferior to xylite. It is observed in most cases as small fragments of pale yellowish coloration, with a fairly well preserved medium- and large-cellular structure.

Algae are lilac-gray, as in bright coal of type I. They are noted here in small number and chiefly in the form of small fragments in the main mass of durite and clarite-durite.

Of the mineral inclusions, only pyrite could be established with certainty. Its very fine grains are visible, sparsely scattered in the main mass of durite and clarite-durite. The pyrite content here is so small that, in the counts, it did not find expression even in fractions of a percent.

The considerable content of xylite and the comparatively very small amount of fusite indicate that the numerous bands of hard fusite visible to the naked eye are in reality bands of xylite, since the quantity

their quantity, noted macroscopically, in no way corresponds to the quantity of fusite formations established under the microscope. The macroscopically observed weak silky luster (somewhat less intense than that of fusite) and the considerable hardness of these bands are fully consistent with their xylitic nature. The silky luster is explained by the fact that the tissue in them is not yet completely filled and therefore retains certain physical properties characteristic of fusite, in particular a luster similar to it. The rather high hardness of these bands is explained by the cementing action of the colloidal organic mass, which here already fills a considerable part of the tissue. All this gives grounds for considering the macroscopically visible lenses of hard fusite to be xylitic.

Dwelling briefly on the microscopic features of both kinds of bright coal, it is necessary first of all to note the high content, in both, of clarito-durite. This fact deserves serious attention because clarito-durite in our coals belongs among the sintering ingredients. A second feature of this group of coals is the comparatively high content in them of vitrite, clarite, and the principal structureless mass of durite, with a very small content of various fusainized formations. The percentage ratio in the group between vitrite, the principal mass of durite, clarite, and clarito-durite, on the one hand, and all fusainized elements, on the other, is expressed approximately as follows: for the former—84.0%, and for the latter—16.0%. Finally, the third feature of the group under consideration is the insignificant content of mineral impurities in the coals. Of the latter, microscopically it was possible to note only a small number of pyrite inclusions, represented in both kinds of coal by separate small grains, chiefly in the principal structureless mass.

Group of dull coals

Dull coal of kind I, under the microscope, proves to be mainly complex durite (88%) and partly xylite (10%); the remaining ingredients take an insignificant part in the composition of the coal, and their total content barely reaches 2 percent.

An essential feature of this kind of coal is the complete absence in it of clarite and a stronger saturation with fusainized formations of the principal mass of durite. Owing to the latter circumstance, the quantitative ratio in the coal of vitrite and the principal mass of durite, on the one hand, and of fusainized formations, on the other, changes substantially in favor of the latter: fusainized formations account for 59% of the coal thickness, while the structureless mass of durite and vitrite account for only 41%. Such a ratio of the constituent parts determines the dull luster of the coal.

The content of fusainized formations and of the principal mass in the durite is, respectively, 48 and 40%. The principal mass in the durite is light gray, structureless, and not fissured. Among the fusainized formations the most widely distributed are small lilac-gray fragments of irregular elongated form, spores, fragments of spores, small fragments of xylitic tissue, etc. All these formations are distributed in the principal mass of the durite more or less uniformly. The bands and areas of clarito-durite observed in the coals of the bright group are absent here.

Vitrite has a light-gray color, is very little fissured, and is observed as few and small lenses of structureless appearance. The most common thickness of the lenses is 0.02–0.03 mm. Bands of vitrite with a thickness up to 0.1 mm are rarely encountered.

Xylite is predominantly of type I and is observed in the coal in the form of small

fragments, fairly evenly scattered among the other formed constituents. These fragments, despite their small size, gave, in micro-counts, an overall high percentage content (up to 10%). The coloration of the xylite fragments, as in the preceding coals, is faintly yellowish, sometimes light gray. The structure is coarse- and medium-cellular, very rarely fine-cellular.

Fusite, like xylite, occurs as small fragments and in most cases with a more or less well-preserved cellular structure. The cellulose in them is fairly thick-walled, not mineralized, has a fine- and medium-cellular structure and a faint yellowish coloration. Coarse-cellular, and also light-gray fusite, is a comparatively rare exception. Remains of algae of a lilac-gray color are distributed here in somewhat greater quantity than in the coals of the preceding group. They are strongly destroyed and are observed as small irregularly shaped fragments, more or less uniformly scattered in the durite.

Among the mineral formations, inclusions of pyrite deserve attention; these, as in the bright coals, are few in number, small in size, and occur chiefly in the main structureless mass of the durite. Sometimes individual grains of pyrite are observed in fragments of plant cellulose, in spores, and even in fragments of lilac-gray algae. The total pyrite content is somewhat higher than in the coals of the first group, but nevertheless even here it does not amount to fractions of a percent.

In addition to pyrite inclusions, dark-gray mineral inclusions were distinguished in the described variety, which, as in the Gigant and Sbrosovyi seams, we assigned to sandy-clayey formations. These inclusions are incomparably larger and more numerous than pyrite grains. They amounted to more than 1% of the entire coal thickness studied in thin sections.

Dull coal of type II, macroscopically characterized as a coal approaching combustible shale, differs very substantially not only from dull coal of type I in the given seam, but in general from all the dull coals of the seams described above. Microscopically it presents a rather distinctive picture both in the quantitative and qualitative composition of the ingredients composing it. Its principal ingredients are durite (82%) and vitrite (12%). Of the other ingredients, xylite is observed in a very limited quantity (fractions of a percent), and fusite, quantitatively, at the scale of our work, could not be accounted for. Clarite and clarite-durite are completely absent. Instead of them, a rather significant content of clayey material appears in the coal—up to 5%. Thus, the features of this coal variety are: a high content of durite and vitrite, a very low content of xylite and fusite, and a significant content of clayey material. In addition, a very essential feature of the coal is the distinctive composition of the durite. The latter is characterized here by a very great saturation with formed elements, represented by extremely small lilac-gray algal fragments. Such fragments are probably the remains of a strongly destroyed filamentous alga and, being very numerous in the coal, account for the considerable yield of volatiles in it (up to 55% on the combustible mass). In addition, fragments of lilac-gray algae, spores, spore fragments, fragments of thick and thin cuticles, and finally very small and numerous fragments of xylitic, less often fusitic, tissue take part in the composition of the structural part of the durite. All these fragments are fairly uniformly distributed in the main mass of the durite and are usually distinguished by their small size.

Vitrite, as already noted above, plays a very substantial role in this coal.

plays a substantial role, making up to 12% of its thickness. Microscopically it appears as narrow, but comparatively long bands, arranged strictly according to the bedding. Their thickness on average varies within the limits of 0.05–0.1 mm and only in rare cases reaches 0.3–0.4 mm. They are completely unfractured, have a light-gray coloration, and do not bear any structure. Sometimes along the margins of such lenticles one can observe a poorly preserved cuticle.

Xylite occurs in very sparse and usually very small fragments of yellowish coloration, with a medium- and fine-cellular structure. The overwhelming majority of fragments belong to type-I xylite. Because of their small size (less than 0.007 mm), xylitic inclusions in microscopic counts were assigned chiefly to the number of shaped elements of durite, owing to which the content of xylite as an independent ingredient, being in general very small, was reduced still further.

Fusite occurs in vanishingly small quantity, in the form of very small fragments, often consisting of only two or three half-destroyed cells. The small size of these fragments, as also in the case of xylite, prevented their being counted separately from the shaped formations of durite.

Mineral inclusions in the coal described, besides pyrite and dark-gray grains of quartz, are also represented by clayey interlayers. Pyrite is observed mainly as separate small grains in the main mass of durite, and rarely as a filling substance in structural formations. In several cases pyrite grains were noted as grouped into small patches, which was not observed in other cases. In general, pyrite in this variety of coal plays a more substantial role than in all the preceding cases. Clayey interlayers are also developed in a rather significant quantity. Under the microscope they appear as narrow gray-black bands, sometimes containing separate shaped inclusions and, in particular, spores. It is not without interest to note that in some of these clayey bands macrospores—generally rare for the seam—and even tetrads of them were encountered.

The distribution of macrospores in the clayey interlayers of the coal is interesting from the genetic standpoint, indicating a substantial role of drift phenomena in the accumulation of the primary plant matter of this coal. (The microflora of clayey deposits has recently been elucidated by the works of Prof. P. A. Nikitin.)

Thus, the principal features of the group of dull coals are: an increased content of various shaped formations and a decreased content of vitrite in the main structureless mass of durite (for the group as a whole this is expressed, respectively, as 56% and 44%); the substantial role, among the shaped formations, of spores and algae; and the comparatively high content of mineral impurities, which worsen the caking capacity and increase the ash content of these coals.

On the basis of microscopic study, the dull coals of the seam may be classified as duritic.

The most important data on the microcomposition of the coals are brought together in Table 21.

Specific gravities of the coals and technical composition

The results of determinations of the specific gravities of the coals are given in Table 22. As is evident from the table, the lowest specific gravity is characteristic of bright coal of variety II, although by analogy with the seams studied earlier it would seem that bright coal of variety I should have the lowest specific gravity. This discrepancy in the present case should probably be attributed to the somewhat higher content in bright coal of variety I of mineral—

Table No. 22.

Specific gravities of the ingredients of the Nikolsky seam.

No.	Name of ingredients	Number of determinations	Extreme values of specific gravities	Mean values of specific gravities	Note
1.	Lustrous coal of the 1st kind . . .	103	1.16–1.22	1.19	A large number of pieces have a weight of 1.16 (40 pieces) and 1.17 (37 pieces).
2.	Lustrous coal of the 2nd kind . . .	121	1.16–1.18	1.17	The majority of pieces have a specific gravity of 1.16 (72 pcs.).
3.	Dull coal of the 1st kind . . .	67	1.24–1.39	1.28
4.	Dull coal of the 2nd kind . . .	15	1.30	1.30	All pieces showed a specific gravity of 1.30.

mineral impurities in the form of the finest grains of pyrite and, in part, small films of calcite, which here it was possible to detect by means of roentgenoscopic investigation carried out by Prof. I. A. Sokolov.

Dull coals, as being more mineralized, are distinguished by a higher specific gravity. This circumstance opens up the possibility of separating lustrous coals from poorly or almost non-caking dull ones. However, it must be noted that the success of beneficiation here will be hindered by the comparatively small difference in the specific gravities of lustrous and dull coals, the insignificant thickness of many interbeds of dull coal of the 1st and 2nd kinds (0.5–1 mm), and, finally, the probably low specific gravity of the dull coal that enters, in the form of narrow bands, into the composition of lustrous coal of the 1st and 2nd kinds. For technical reasons we were unable to determine precisely the specific gravity of the dull coal included in the composition of the lustrous coals. But, in any case, it will be small; otherwise, the lustrous coal of the 2nd kind, strongly enriched with bands of this coal, would not have such a low specific gravity (1.17).

The data of the technical analysis, summarized in Table 23, show that the coal of the Nikolsky seam is a typical coal of the Minusinsk basin. The only exception is the dull coals of the 2nd kind from the second band (analyses Nos. 13 and 14), which give almost 56% volatile matter in the combustible mass, whereas their average content in the other coals is about 42%. This fully corresponds to the nature of these coals, which are close to combustible shales.

Of considerable interest, further, is the fairly good caking capacity of the lustrous coals, especially of the first kind, which give a caked, fused, though weakly swollen bead. The caking capacity is lower in lustrous coals of the second kind and weak in the dull coals, as also in the average sample for the seam. It also deserves attention that a mixture of lustrous coals in a ratio of 1:1 gives a coke bead of the same properties as the lustrous coal of the first kind.

As in the case of the Sbrosovy seam, the increased caking capacity of the coal of the Nikolsky seam, compared with the Chernogorsk coals, can hardly be …

Table No. 23.

Proximate analysis of coal from the Nikolsky seam.

No.	Sample characterization	\(W^a\)	\(A^a\)	\(V^a\)	\(V^r\)	\(K^a\)	\(K^r\)	Characterization of the coke button
1.	Bright coal, variety I, from bench 1	5.69	3.33	37.57	41.29	56.71	58.71	Caked, fused, very slightly swollen.
2.	Bright coal, variety I, from bench 1	4.89	3.34	38.88	42.58	56.23	57.42	Caked, fused, very slightly swollen.
3.	Bright coal, variety I, from bench 2	5.37	4.04	39.17	43.24	55.46	50.76	Caked, fused, almost not swollen.
4.	Bright coal, variety I, from bench 2	3.96	6.49	39.66	44.74	55.38	55.26	Caked, fused, very slightly swollen, dense.
5.	Bright coal, variety I, from bench 3	3.26	5.32	40.23	44.01	56.51	55.99	Caked, fused, very slightly swollen.
6.	Bright coal, variety I, from bench 3	2.99	2.93	40.26	42.79	56.75	57.21	Caked, fused, very slightly swollen.
7.	Bright coal, variety II, from bench 1	3.95	3.81	40.33	43.72	55.72	56.28	Caked, fused, almost not swollen.
8.	Bright coal, variety II, from bench 1	5.74	3.44	37.23	40.99	57.03	59.01	Weakly fused, very slightly swollen.
9.	Bright coal, variety II, from bench 1	4.87	3.33	38.51	41.95	56.62	58.05	Caked, partly fused, very slightly swollen.
10.	Bright coal, variety II, from bench 2	3.10	5.74	39.86	43.73	57.01	56.27	Caked, fused, almost not swollen.
11.	Dull coal, variety I, from bench 1	4.74	14.18	25.90	31.94	69.36	68.06	Sintered, steel-gray in color.
12.	Dull coal, variety I, from bench 1	3.39	31.25	29.15	44.60	67.46	55.40	Sintered, coal-black.
13.	Dull coal, variety II, from bench 2	3.11	26.61	37.37	53.18	59.52	46.82	Sintered, steel-gray in color.
14.	Dull coal, variety II, from bench 2	1.64	37.65	33.89	55.82	64.97	44.18	Sintered, coal-black.
15.	Average sample over the entire seam	7.93	12.10	30.98	38.74	61.09	61.26	Sintered, coal-black.
16.	Mixture of bright coal of varieties I and II in the ratio 1:1.	Determination was made only of the caking capacity	Determination was made only of the caking capacity	Determination was made only of the caking capacity	Determination was made only of the caking capacity	Determination was made only of the caking capacity	Determination was made only of the caking capacity	Fused, dense, steel-gray in color, completely unswollen.
17.	Same	Determination was made only of the caking capacity	Determination was made only of the caking capacity	Determination was made only of the caking capacity	Determination was made only of the caking capacity	Determination was made only of the caking capacity	Determination was made only of the caking capacity	Very slightly swollen, caked, fused.
18.	Same	Determination was made only of the caking capacity	Determination was made only of the caking capacity	Determination was made only of the caking capacity	Determination was made only of the caking capacity	Determination was made only of the caking capacity	Determination was made only of the caking capacity	Caked, fused, almost not swollen.

can be explained only by one difference in the petrographic composition of the coals. In general, the composition of the Chernogorsk and Izykh coals is very similar. In the coal of the Nikolsky seam, as in that of the Sbrosovy seam, only the reduced content of xylite and fusite deserves attention.

The increase in the caking capacity of the coal of the Nikolsky seam should be attributed to its higher degree of coalification.

DEPOSIT OF THE KALYAGIN EXPLORATION. (NARYLKOVSKOE).

VII. The Dvenadtsatiarshinny Seam.

MACRODESCRIPTION.

Sampling of the seam was carried out in exploration shaft No. 1 of the coal exploration section of Kuzbassugol. Samples could be taken only from the second band of the seam, located at a depth of 40 m. It was not possible to sample the lower bands, lying at deeper levels (45–54 m), for technical reasons. The second band has a total thickness of 1.61 m. Coal accounts for 1.51 m and barren rock for 0.09 m. The latter is usually represented by light-gray fine-grained sandstone, forming interbeds from 0.05 to 2.25 cm.

In the macroscopic study it was possible to divide the coal of the band into three kinds: two dull kinds and one kind of bright coal. In addition, vitrite and fibrous coal were separately distinguished. The content of all macrocomponents is given in Table No. 24.

Bright coal of kind I, after vitrite, is the brightest in the band. Its luster approaches resinous. The color is black. The fracture is comparatively even. The texture is banded. The banding is expressed indistinctly by alternation of the main, comparatively weakly lustrous mass with thin bands of brightly lustrous vitrite and still thinner (fiber-like) bands of dull coal. The coal is rather firm, little broken by cleavage cracks. However, the latter are more numerous in it and appear much more strongly than in dull coals. They cut the coal at right angles to the bedding and give very even surfaces.

Table No. 24.
Macroscopic composition of coal.

Kinds of coal	Probable nature of the coal	Thickness of the kind in the band, cm	% of band thickness
Bright coal of kind I	Clarite coal	9.5	6.0
Dull coal of kind I	Durito-clarite coal	71.6	45.0
Dull coal of kind II	Durite coal	36.7	23.0
Vitrite coal	Vitrite	19.5	12.0
Fibrous coal	Fusite	13.7	8.0
Mineralized fibrous coal	Fusite	1.6	1.0
Barren rock (gray fine-grained sandstone)		8.3	5.0
Total		161.0	100

Coal of this kind usually forms narrow bands in the band, most often 0.2–0.4 cm thick, and almost always in direct association with vitrite (see the petrographic section of the seam, Fig. 32).

Dull coal of kind I is characterized by a heterogeneous luster approaching dull-greasy. The texture of the coal is clearly banded; coal

Petrographic section of the “Twenty-Arshin” seam of the Narylkovo Mine.

Fig. 32.

Legend:

• Vitrite
• Bright coal, type I
• Dull coal, type I
• Dull coal, transitional type
• Fusain
• Coaly argillite
• Argillite
• Sandstone

Scale: 1 cm = 2 centimeters.

consists of alternating basic matte-greasy bands, thin bands of resinously lustrous coal, and less numerous vitrite and fusite lenses. The fracture of the coal is uneven, of medium coarseness. The color is from dark gray to gray-black. Cleat cracks are rather few; they run in a direction perpendicular to the bedding and in most cases are weakly expressed. The cleat surfaces here are less even than in lustrous coal of variety I; the fracture is longitudinally streaky, that is, slightly splintery.

The coal is developed mainly in the middle part of the bench, in the form of interbeds of small thickness. The latter sometimes increases somewhat, reaching 1–2.5 cm and even more.

Matte coal of variety II has a matte-greasy luster, a dark-gray color, and a banded texture. The banding is expressed comparatively weakly and is due to the presence, in the main matte mass of the coal, of very thin lenses of vitrite and fusite. The coal is distinguished within the seam by its greatest toughness and the smallest content of cleat cracks. The latter are rare in it and weakly expressed; they cut the coal perpendicular to the bedding. The fracture of the coal is uneven, of medium coarseness. The coal is developed predominantly in the upper part of the bench, as interbeds from 0.2 to 2.0 cm and more in thickness.

Vitrite coal possesses a massive structure, a glassy-resinous luster, and comparatively very low toughness. It is observed in the bench in the form of small and narrow lenses, the thickness of which in most cases does not exceed 0.1 cm and only rarely reaches 0.3–0.4 cm.

Fusite occurs as both hard and soft varieties, the latter predominating. Inclusions of soft fusite have a rather strong silky luster, a black color, and strongly soil the hands. Inclusions of hard fusite (microscopically usually xylite and fine-cellular fusite) are characterized by a less intense silky luster and a less pronounced soiling property.

Inclusions of mineralized fusite are also encountered. On surfaces perpendicular to the bedding they appear as small light-gray lenses, and on bedding surfaces—as small films with a faintly discernible fibrous structure. This latter circumstance alone makes it possible to assign these inclusions macroscopically to fusite.

Soft and hard fusite is observed on bedding surfaces in the form of small, not very numerous films with a more or less intense silky luster. These films, being of very small thickness, remain almost unnoticeable on planes perpendicular to the bedding, as a result of which only the largest of them are recorded in the petrographic section (Fig. 32).

From the section it is evident that fusite bands are observed chiefly in the middle part of the bench and, mainly, in matte coal of variety I. Mineralized fusite enriches the lower part of the bench and is here associated with matte coal of variety II. Among mineral inclusions it was possible to note only a few, but comparatively large, films of pyrite, situated on certain cleat surfaces. Fig. 32 and Table 24 show the distribution in the seam of the described varieties of coal.

MICRODESCRIPTION

Lustrous coal of variety I under the microscope proves to be composed mainly of clarite (up to 85%), partly of durite (not more than 10%) and vitrite (up to 5%) (see Table No. 25).

Clarite presents a typical picture: it consists chiefly of a principal light-gray mass and of thin and thicker cuticles immersed in it. Thin cuticles are fairly numerous and are arranged irregularly—

Table No. 25.
Micropetrographic composition of the Dvadtsatimarshinnyi coal seam
in percent

Coal type	Durite composition: main structureless mass	Durite composition: spores	Durite composition: small fragments of cuticles, fusite and xylite cellular tissue, and other structural formations of organic origin	Formed inclusions: total structural formations	Formed inclusions: total durite	Clarite composition: main structureless mass	Clarite composition: cuticles and resin bodies	Clarite composition: total	Vitrite	Xylite: type I xylite	Xylite: type II xylite	Xylite: total	Fusite: fusite	Fusite: mineralized fusite	Fusite: total	Mineral inclusions: concretions of iron oxides	Mineral inclusions: other mineral inclusions	Mineral inclusions: total	Total	Percentage content of the coal type in the bench	Notes
Shiny coal, grade I	9.0	—	1.0	1.0	1.0	10.0	82.0	—	3.0	85.0	5.0	—	—	—	—	—	—	—	—	100	6.0
Dull coal, grade I	49.0	1.0	17.0	18.0	67.0	2.5	—	2.5	2.5	18.0	10.0	—	2.0	12.0	9.5	0.5	10.0	—	0.5	100	45.0
Dull coal, grade II	46.0	1.0	19.0	20.0	66.0	—	—	—	3.0	—	18.0	—	12.0	—	12.0	traces %	traces %	1.0	1.0	100	23.0

uniformly, in separate layers and, in most cases, are closely brought together with one another. The thicker cuticles are distributed more evenly, are less closely spaced, and are observed in smaller numbers. The maximally thick cuticles, encountered in the clarite and durite of the beds described above, have not been noted here.

In addition to cuticles, the clarite contains, in very limited quantity, inclusions of light-gray bodies (above, we recorded them partly as resin bodies, partly as spores). No other inclusions were found in the clarite, which indicates its fairly high purity.

Under the microscope, durite is characterized by a very small content of formed elements and in its composition approaches durito-clarite. Among the formed structures in it, the greatest volume is occupied by small fragments of fusite and xylite tissue. These are followed by small fragments of cuticles, lilac-gray fibrous inclusions, spores, fragments of individual cells, and other small inclusions.

The high content of clarite and the claritic character of the durite in the coal make it possible to call it a claritic coal. The decisive predominance of the main mass in it accounts for its strong macroscopic luster.

Vitrinite of the usual type is developed in the coal as sparse, but sometimes rather large, lenses alternating with clarite.

Mat coal of the I seam is essentially a duritic coal: in it, durite accounts for as much as 67%, and all other ingredients together for only 33%. The other ingredients are represented here as follows: vitrinite—8%, xylite—12%, fusite—10%, and finally clarite—2%, and mineral inclusions—fractions of a percent (see Table No. 25). Durite is distinguished by a comparatively high content of formed elements, amounting in total to about 30% of its volume in thin sections (the remaining 70% in it belongs to the basic structureless mass).

Among the formed structures, the most widespread in the durite are small fragments of xylite and fusite tissue, fragments of cuticles, and small lilac-gray formations, usual for Minusinsk coals. Next in volume come fragments of spores, whole spores, fragments of individual cells, and other small inclusions.

Clarite of the same type as in the preceding seam occurs as thin and sparse bands among the durite.

Vitrinite is light gray, strongly fissured, and of structureless appearance. It is observed as rather numerous and not infrequently comparatively large lenticules.

Xylite of type I predominates; it occurs chiefly as small fragments of light-yellowish color, with fine- and medium-cellular structure. Coarse-cellular xylite, as well as xylite of light-gray color, occurs comparatively rarely.

Fusite, like xylite, is developed in most cases as small fragments and lenses of light-yellowish, sometimes light-gray color. Their tissue is fine-, medium-, more rarely coarse-cellular, often strongly destroyed, so that many fusite lenticules appear as if completely knocked out. Such lenses correspond to the soft variety of fibrous coal in its macroscopic sense. Often the fusite tissue can be observed to be mineralized.

Of the individual mineral inclusions, only pyrite could be firmly recorded, usually in the form of small inclusions in the main mass of the durite. In addition, a few clayey bands of insignificant size were also noted; in the counts they amounted to less than fractions of a percent.

The presence of clarite and durito-clarite places this coal variety among the durito-clarites.

Dull coal of the II variety differs from dull coal of the I variety chiefly in a higher content of formed constituents and a lower content of the principal structureless mass and vitrite.

The following ingredients take part in the composition of the variety described: durite—66%, xylite—18%, fusite—12%, vitrite—3%, and mineral inclusions—1% (see Table No. 25). Durite thus remains the principal ingredient here as well. It has the same composition as the durite of dull coal of the I variety, but differs in another quantitative ratio of ingredients. Above all, it gives a somewhat higher content of formed elements (30%) and, correspondingly, a lower content of the principal mass (70%, instead of the 76% present in the durite of dull coal of the I variety)¹. Further, in the durite of this coal variety fewer cuticles and their fragments are observed, but on the other hand there are many times more fragments of fusite and xylite tissue, and partly fragments of spores.

Xylite, fusite, and vitrite, not included in the composition of the durite but counted as independent ingredients, remain, in their appearance, size, and character of distribution, approximately identical with these same ingredients in dull coal of the I variety. They differ from the latter only quantitatively, showing here a somewhat higher content.

The mineral inclusions are the same as in the preceding variety, but occur here in greater quantity.

Specific gravities

The results of determinations of specific gravities are brought together in Table No. 26 and give the same sufficiently regular picture of a gradual increase in specific gravity from the more lustrous to the duller coals as in other deposits.

Table No. 26.

Specific gravities of coals of the Dvenadtsatiarshinnnyi seam.

No.	Name of coal varieties	Number of determinations	Extreme values of specific gravities	Mean values of specific gravities
1	Vitrite	10	1.17–1.18	1.17
2	Lustrous coal of the I variety	10	1.16–1.22	1.18
3	Dull coal of the I variety	10	1.23–1.30	1.26
4	Dull coal of the II variety	10	1.26–1.34	1.30

Note. The specific gravities were determined, for technical reasons, with approximate accuracy.

Table 27 shows the data of the proximate analysis of the coals of the Dvenadtsatiarshinnnyi seam. The coals are characterized by the same technical properties—

than those described above. But the seam as a whole shows no caking capacity either for the individual coal varieties or in the average sample. In this respect the coal of the deposit of the Kalyagino prospecting area occupies the last place among all those described above.

Table No. 27

Results of technical analyses of coal from the Dvenadtsatiarshinny seam.

No.	Sample description	\(W^a\)	\(A^a\)	\(K^r\)	\(V^r\)	\(V^a\)	\(K^a\)	Coke button characteristic
1	Vitrite coal	6.51	1.52	59.55	40.45	37.20	56.29	Slightly caked
2	Bright coal, variety I	7.66	2.76	58.41	41.59	37.50	54.84	Does not cake
3	" " "	6.53	5.54	58.09	41.91	36.85	56.62	Does not cake
4	Dull coal, variety I	6.99	6.19	62.12	37.88	32.89	60.12	Does not cake
5	" " "	4.94	10.80	59.76	40.24	33.71	61.35	Does not cake
6	" " "	7.15	9.92	60.15	39.85	33.05	59.80	Does not cake
7	" " "	4.41	9.86	62.16	37.84	32.44	63.15	Does not cake
8	" " "	6.32	8.24	69.74	30.26	25.85	67.83	Does not cake
9	Dull coal, variety II	5.01	16.37	68.46	31.54	24.80	70.19	Does not cake
10	" " "	6.02	18.77	64.23	35.77	26.90	67.08	Does not cake
11	" " "	5.81	14.71	69.96	30.02	23.85	70.31	Does not cake
12	Soft fusite	3.02	13.97	82.47	17.53	14.55	82.43	Does not cake
13	Hard fusite	3.80	25.55	73.07	26.93	19.03	77.17	Does not cake
14	Average seam sample	5.89	13.08	63.28	36.72	29.75	64.36	Does not cake

NOTE: The analyses were carried out in the chemical laboratory of the SKhGI.

The coals of the Kalyagino prospecting area have a distinctive petrographic composition. True, they retain, like the coals of the other deposits, a general clarite-durite character. But what is essentially new in this seam is the sharply increased content of clarite. Thus, in the bright coal of variety I the clarite content rises to 85%, with the durite content decreasing to 10%. The same ingredients in the bright coal of variety I of the Gigant seam of the Chernogorsk deposit amount to: clarite—21% and durite—66%. In addition, the durite of the coal of the Dvenadtsatiarshinny seam is characterized by a low content of formed elements and likewise acquires a claritic character. Clarite is also present in dull coals of variety I, whereas it is completely absent in the same coal of the Gigant seam.

In general, the petrographic composition of the coal of the Kalyagino prospecting area is close to the composition of the Jurassic hard coals of the Irkutsk coal basin and of some districts of the Kansk basin (the Sayano-Partizansky district). Hence it is still premature to draw a conclusion about the Jurassic age of the coals of the Kalyagino prospecting area¹. But stratigraphically the deposit occupies the highest position in the Minusinsk basin. The low degree of coalification of the coals of this deposit, in connection with this, makes understandable the absence of caking capacity.

VIII. Conclusion.

The petrographic study of the Minusinsk coals, carried out by the authors for the seams—Gigant, Moshchny, Velikan, and Dvukharshinny of the Chernogorsk deposit; for the Sbrosovy and Nikolsky seams of the Izykh deposit; and for the Dvenadtsatiarshinny seam of the Kalyagino prospecting area (Narylkovo)—was based on sampling each of the named seams only at one

¹ The latter, however, is possible—as Academician Arkhangelsky has already indicated.

at this point and therefore is still far from complete. But it gives a concrete idea of the petrographic composition and nature of the Minusinsk coals, outlines the conditions of accumulation of the primary plant substance, and to a certain extent clarifies the question of their caking capacity.

The Minusinsk coals have a rather complex petrographic composition. The entire variety of coals composing the seams, macroscopically, fits rather well into two large groups—bright and dull coals—which, in the studied samples of the seams, are distributed more or less evenly. Thus, in the Gigant seam, bright coals make up almost 45% of the thickness of the seam (49% in the second bench and 40% in the third). In the Sbrosovyi seam they amount to 52% (54% in the first bench, 53% in the second, and 42% in the third). In the Nikol’skii seam they reach 69% (66% in the first bench, 75% in the second, and 77% in the third). Both bright and dull coals most often alternate with one another in thin interlayers, the thickness of which only in rare cases reaches 20 cm, and usually does not exceed 3–5 cm (dull coals sometimes form layers more than 20 cm thick). This determines the banded texture characteristic of Minusinsk coals.

According to the degree of luster and dullness of the coals, and also according to other physical properties, such as fracture, texture, fissuring, and color, the two large groups named above are macroscopically easily subdivided into smaller ones, which we have distinguished under the name of varieties with ordinal numbers increasing as the luster weakens. The varieties of coal are distributed unevenly in the seams. Thus, the most interesting among them, the bright coals of varieties I and II, which are distinguished by the highest degree of caking, while playing an essential role in the composition of some benches, are poorly developed in others. For example, in the Sbrosovyi seam, variety I of bright coal constitutes 40% in the first bench, 19% in the second, and 4% in the third. In the same seam, variety III gives, by benches: 1—14%, 2—34%, and 3—38%. The same coals in the Nikol’skii seam give: variety I, in bench 1—29%, 2—72%, 3—67%; variety II, in bench 1—37%, 2—3%, 3—10%. Bright coals form interlayers only 0.5–2 cm thick, more rarely 6–8 cm. But in the Gigant seam, varieties I and II of bright coals together form, near the floor of the seam, an interlayer 17.5 cm thick.

The varieties of coal that we have distinguished, with the exception of the particularly distinctive coals of the Narylkovo field (the Dvenadtsatiarshinnyi seam), and also mineralized coals (for example, variety III of bright coal and variety II of dull coal of the Gigant seam), represent more or less persistent types, preserving in the better-studied seams both physical properties and general petrographic composition. This must especially be said of variety I of bright coals, which in the Gigant, Sbrosovyi, and Nikol’skii seams reveals a clarite-durite composition. In addition to a rather high content of clarite (usually, however, less than 30%), in the named seams, especially in the Sbrosovyi seam, clarite-durite plays a significant role in bright coal of variety I; it is observed in the form of the main structureless mass of durite with vitrinitized cellular tissue of clarite. All the other varieties of bright coals, by composition, are durite-clarite types, while all dull coals are durite types of coal.

Thus, for example, in the Gigant seam we distinguished, in the group of bright coals: variety I—clarite-durite coal; variety II—durite-clarite coal; and variety III—mineralized durite-clarite coal. In the subdivision of dull coals, besides composition, the texture of the coals was also reflected. Here we distinguished: variety I—banded durite coal; variety II—mineralized durite coal; variety III—massive durite coal; variety IV—durite-fusite coal.

Of these varieties, the most persistent in other seams proved to be: varieties I and II of bright coals and variety I of dull coals. This can be judged, for example, from the specific gravities of the coals. Thus, varieties I and II of bright coals in

in the Gigant seam have specific gravities of 1.21 and 1.22, respectively. The same two types of coal in the Sbrosovyi seam also have specific gravities of 1.21 and 1.22. Dull coal of the first type from the Gigant seam gives a specific gravity of 1.24; the same coal of the Sbrosovyi seam has a specific gravity of 1.26. In the Nikol’skii seam the specific gravities of these coals already show more noticeable, although still small, deviations. But in the other distinguished types of coal the physical properties, as well as the specific gravities, already show considerable discrepancies, which, for mineralized coals—especially dull coals, in which rather high and often secondary mineralization always plays a large role—must be considered quite natural.

The special position of the coals of the Dvenadtsatiarshinnyi seam of the Narylkovo deposit, mentioned above, consists in the fact that clarite plays an essential role in their composition. In the Gigant seam, for example, the content of durite coal and clarite by coal type is distributed, respectively, as follows: first type of bright coal—66% and 21%; second type—78% and 1%; third type—67% and 2%; first type of dull coal—72% and 0%. Meanwhile, in the Dvenadtsatiarshinnyi seam the same components are distributed as follows: first type of bright coal—10% and 85%; first type of dull coal—67% and 2.5%. If, by the percentage content of clarite and durite, the coals of the Gigant seam, as well as those of other seams, should be called durite-clarite coals, then the coals of the Dvenadtsatiarshinnyi seam are clarite-durite coals. In this petrographic composition the coals of the Narylkovo deposit approach the Jurassic coals of the Irkutsk and Kansk basins. And it is possible that the coal-bearing series of the Narylkovo deposit, which occupies the highest stratigraphic position in the district, is of Mesozoic age.

A more detailed microscopic study of clarite, as an ingredient generally having an active role with respect to caking capacity, revealed that in it there are areas close both to clarite and to durite. These are areas with a main structureless mass, analogous to the main mass of durite, and at the same time saturated with formed bodies characteristic of durite. But after etching, vitrinitized cellular tissue of clarite is revealed in the main structureless mass of these areas. Such areas were distinguished under the name clarite-durite. Unfortunately, it was not possible to take quantitative account of such areas, and in the micropoint counts they entered partly into clarite and partly into durite. It should be thought that in the Minusinsk coals they represent a concrete expression of the coalification process. It is very probable that, as coalification develops, the caking capacity of the coals increases during the vitrification of the cellular areas of clarite-durite. The greatest development of such vitrified cellular areas characterizes the coals of the Izykh deposit (the Sbrosovyi and Nikol’skii seams). It was precisely these seams that yielded coals of the highest caking capacity.

Vitrinite plays a subordinate role in the Minusinsk coals. In bright coals its content sometimes reaches 10%, although more often it is considerably lower. In dull coals it is measured at 1–3%; but often vitrinite is entirely absent in these coals. Very small dimensions of the vitrinite lenses are characteristic, both in length and in thickness, the latter being measured in fractions of millimeters and only in exceptional cases reaching up to 3 mm. This may be connected with the primary maternal nature of vitrinite, which on etching reveals affinity to herbaceous plants. The vitrinite of the Minusinsk coals shows a low caking capacity, which can be explained both by its indicated plant nature and by the low degree of coalification.

Fibrous coal (fusite and xylite) in general also plays a subordinate role, although in individual cases its content reaches rather high—

such figures. In the Gigant seam it gives, for example, in bright coal of type II—16%; in bright coal of type III—19%; in dull coal of type I—20%; in dull coal of type IV—32%. In all these cases, fibrous coal, of course, lowers the caking capacity of the entire mass of coal of the given type.

Next, attention is deserved by mineral formations, which occur either as very thin interlayers (clayey), as crusts and films or, more rarely, as local accumulations (pyrite), or which not infrequently have a finely disseminated character (clays and calcite). The latter type of mineral inclusions may also play the role of a factor reducing caking capacity.

The disseminated character of the mineral inclusions, together with the grassy and leafy parent plant material of the coals and the abundance in some types, especially dull coals, of formed bodies such as spores, fragments of cuticle, etc., may indicate the significant role, in the process of accumulation of the primary parent material of the Minusinsk coals, of drift phenomena and, at the same time, the allochthonous character of these coals in part.

The features indicated above in the primary plant nature, structure, petrographic composition, and degree of coalification of the Minusinsk coals suggest a number of evident factors behind their generally low caking capacity. Among them, the principal one should apparently be considered the comparatively low degree of coalification. In addition, an undoubtedly significant role is played by the great depth of the oxidation zone in the Minusinsk basin, from which not a single one of the coal samples we studied was free. Then, of course, the complex composition of the coals is also of great importance, owing to which each seam in different parts of the vertical section has a nonuniform caking capacity.

Among the coal types we distinguished, the greatest caking capacity is shown by the bright coals, especially type I and partly type II, as is seen from Table 28.

Table No. 28.

No.	Deposit and seam	Coal type	Character of the coke button
1	Chernogorsk deposit. Seam Gigant	Bright type I	Weakly caked
2	Chernogorsk deposit. Seam Gigant	Bright type II	Same
3	Chernogorsk deposit. Seam Gigant	Dull type I	Same
4	Chernogorsk deposit. Seam Gigant	Dull type II	Not caked
5	Chernogorsk deposit. Seam Moshchnyi	Bright type I	Weakly caked
6	Chernogorsk deposit. Seam Moshchnyi	Bright type II	Very weakly caked
7	Chernogorsk deposit. Seam Moshchnyi	Dull type I	Same
8	Chernogorsk deposit. Seam Moshchnyi	Dull type II	Sintered
9	Izykhskoe deposit. Seam Sbrosovyi	Bright type I	Caked, fused, weakly swollen, dense, fairly strong, silvery-lustrous.
10	Izykhskoe deposit. Seam Sbrosovyi	Bright type II	Caked, slightly fused, with cracks, silvery-lustrous.
11	Izykhskoe deposit. Seam Sbrosovyi	Dull type I	Caked, black with cracks.
12	Izykhskoe deposit. Seam Sbrosovyi	Average sample over the seam	Weakly caked, black
13	Izykhskoe deposit. Seam Nikolsky	Bright type I	Caked, fused, weakly swollen.
14	Izykhskoe deposit. Seam Nikolsky	Bright type II	Caked, fused, very weakly swollen.
15	Izykhskoe deposit. Seam Nikolsky	Dull type I	Sintered, gray-black in color.
16	Izykhskoe deposit. Seam Nikolsky	Average sample over the seam	Sintered, coal-black in color.

The table presented shows a rapid decrease in caking capacity from bright to dull coals. The best caking was given by the bright coals of the Izykhskoe deposit, especially of the Sbrosovyi seam, despite the slight

List of References

1. Zalesskii, M. D. Microscopic structure of coal from the lower bench of the “Velikan” seam of the Chernogorsk mines of the Minusinsk Basin.—Materials on General and Applied Geology, issue 92, 1929.

2. Ergol’skaia, Z. V. Description of the microscopic structure of coal from the “Dvukharshinnyi” seam of the Chernogorsk mines of the Minusinsk Basin.—Transactions of the Main Geological Prospecting Administration, issue 4, 1930.

3. Elovskii, V. A. Description of the microscopic structure of coal from the “Moshchnyi” seam of the Chernogorsk mines of the Minusinsk Basin.—Transactions of the GGRU, vol. 4, 1930.

4. Maier, L. M. and Tsukerman, L. E. Macro- and microscopic investigation of Krasnodon coals of the Donbass.—Coke and Chemistry, 1932, No. 7.

5. Luber, A. Types of transformation of plant tissues into coal.—Chemistry of Solid Fuel, 1934, No. 5.

6. Maier, L. M. and Chernyshev, D. M. Influence of individual petrographic components of coal on the reactive capacity of coke.—Coke and Chemistry, No. 8, 1932.

7. Ammosov, I. I. Materials on the petrography of Leninsk coals of Kuzbass.—Novosibirsk, 1933.

8. Ammosov, I. I. New data on the petrography of Kuzbass coals.—Collection on the Geology of Siberia. Tomsk, 1933.

9. Zhemchuzhnikov, Yu. A. and Ginzburg, A. I. Petrographic characterization of coals of the Cheremkhovo deposit.—Chemistry of Solid Fuel, 1935, No. 5.

10. Zhemchuzhnikov, Yu. A. Introduction to the petrography of coals. 1934.

11. Zhemchuzhnikov, Yu. A. General geology of caustobioliths. 1935.

12. Potonié, H. The origin of hard coals and other caustobioliths. 1934.

13. Meffert, B. F. On the weathering of mineral coal.—Transactions of the Geological Committee, new series, issue 60, 1910.

14. Karavaev, N. M., Rapoport, P. B., and Koller, V. A. On the weathering of hard coals.—Chemistry of Solid Fuel, 1933, No. 3; 1934, No. 6.

15. Luber, A. A. On the petrographic characterization of Karaganda coals.—Transactions of the All-Union Geological Prospecting Association, issue 358, 1933.

16. Luber, A. A. Petrographic study of the types of coals of Karaganda.—Transactions of TsNIGRI, 1933.

17. Krishtofovich, A. N. Course in paleobotany, 1933.

18. Arkhangel’skii, A. D. Geological structure of the USSR. Western part. Issue 2, 1934.

19. Edel’shtein, Ya. S. Geological sketch of the Minusinsk depression.—Sketches on the Geology of Siberia. Academy of Sciences of the USSR, 1932.

20. Ivanov, G. A. The Minusinsk coal basin.—Mineral Resources of the West Siberian Territory. Vol. III. Coals. 1935.

21. Korovin, M. K. The Minusinsk coal basin in connection with the industrialization of the Khakass-Minusinsk Territory.—Bulletin of ZSGTTr, 1932, issue 1.

22. Korovin, M. K. Several remarks on the question of the coking base in the Minusinsk Basin.—Energy Atlas of the USSR. Western Siberia, 1934.

23. Nikitin, P. A. Annual report on the state of work on the study of the paleomicroflora of Leninsk coals of Kuzbass.—Manuscript (Tomsk Branch of the KBU Research Institute).

24. Potonié, R. Zur Terminologie der petrographischen Bestandteile der Kohle.—Jahrb. d. Preuss. Geol., 1927.

25. Stach, E. Kohlen-petrographisches Praktikum, 1928.

26. Bode, H. Zur Nomenklatur in der Kohlenpetrographie.—Kohle und Erz, 1928, Nos. 18, 24.

1. In relation to the total content of durite. ↩↩↩↩