P. S. Andreev

Petrographic Study of Seam VI of the Inner Prokopyevsk Deposit of Kuzbass, in Connection with the Question of the Variability of Coal Properties

PREFACE

The Kuznetsk Basin is the largest coal basin in the Union, not only in terms of coal reserves, but also in terms of the qualitative diversity of its coals. Here there are sapropelic, humic-sapropelic, and humic coals. Among the latter are brown coals, long-flame coals—gas, fat, coking, steam-caking coals—semi-anthracites and anthracites. However, despite its richest reserves, estimated at 400 billion tons, and the great qualitative diversity of its coals, Kuzbass still remains far from studied, both geologically and, especially, with regard to the quality of its coals.

Chemical investigations of Kuzbass coals have by now yielded enough facts to show that coal from one and the same seam, sampled at different points of its occurrence, gives different quality indices. Facts concerning the qualitative variability of coal from one and the same seam are found in all districts of Kuzbass, but they have been most fully revealed in the Prokopyevsk district. Here almost all seams change their properties both in the direction from south to north and in the direction from west to east.

However, the question of the causes of this variability remains completely open.

For this purpose, it is necessary first of all to determine the petrographic composition of the seams, which, together with the data of chemical investigations of the coal, will make it possible to establish the factors determining this variability. This is important not only from a scientific point of view, but also from a purely practical point of view, since, knowing the factors determining the variability of coal, it is possible to establish regularities and thereby outline the most correct ways of using it.

In the present work, carried out by commission and with funds from the Main Administration of Educational Institutions of the People’s Commissariat of Heavy Industry and performed by me under the supervision of Prof. M. K. Korovin as a postgraduate dissertation, a detailed description is given of the petrographic composition of seam VI of the Inner Prokopyevsk district, based on three seam samples, and a first attempt is made to approach clarification of the question of coal variability.

The entire experimental part of the subject was carried out in the caustobioliths laboratory of the Department of Historical Geology of the Tomsk Industrial Institute.

In the work, besides the direct guidance of the head of the department—Prof. M. K. Korovin—great assistance was rendered to me by the head of the laboratory, Docent I. I. Ammosov, and by the scientific worker of the laboratory, A. B. Travin, for which I express to them my deep gratitude.

All experimental work relating to the petrography of the coals was carried out personally by the author. The chemical analyses were performed by the Department of Pyrogenic Processes of the Tomsk Industrial Institute under the direction of Assoc. Prof. G. R. Shults.

I. Brief Geological Sketch of the Prokopyevsk Coal-Bearing District

The Prokopyevsk coal-bearing district is located on the SSW margin of the Kuznetsk coal basin, 30 km to the NNW of the Kuznetsk Metallurgical Combine.

It has natural geological boundaries only on the east and west: on the east it is bounded by a belt of a coal-barren series, and on the west by the overthrust of the Salair Ridge. To the north and south, however, its boundaries are conventional, since the coal-bearing deposits continue far beyond it in both directions.

Within the district it is divided into two parts, western and eastern, with the boundary between them along the Aba River and the line of the Tomsk Railway, which runs through the entire district almost in a meridional direction.

The geology of the district, on the basis of the latest data, is briefly outlined as follows (1; 2; 5; 6).

In the stratigraphy of the district the oldest deposits are the sediments of the Middle Devonian \((D_2)\), observed along its western boundary. They are represented chiefly by limestones and greenish-gray calcareous shales with interbeds of sandstones. Upon these deposits, unconformably, lie the deposits of the Lower Carboniferous \((C_1)\), represented by limestones, sandstones, sandy-carbonaceous shales, and marls.

The Lower Carboniferous sediments are overlain by the so-called basal conglomerate, 3 to 5 m thick. This conglomerate begins the sequence of nonproductive deposits assigned to the \(H_0\) suite. In the latest stratigraphic scheme of Kuzbass, adopted at the 1934 conference on the stratigraphy of Kuzbass (2), it is distinguished under the name of the Ostrog suite and, by age, is assigned to the Upper Carboniferous \((C_3)\).

Its lithological composition is characterized as follows. Directly upon the basal conglomerate lies a sequence of sandstones of yellowish-greenish color with rare interbeds and lenses of conglomerate and conglomeratic sandstone; higher up this is replaced by yellowish dirty-greenish sandstone interbedded with sandy banded argillite and argillites, and in the upper part also with interbeds of carbonaceous argillite. In the upper part of this sequence two or three coal stringers 0.20–0.30 m thick are observed, accompanied by black carbonaceous argillite with plant remains. Above follow sandstones with several interbeds of conglomerate, composed of pebbles of quartz, hornfels, sandstone with sandy-clayey and ferruginous cement. These conglomerate interbeds are quite well maintained over the entire area of distribution of the \(H_0\) suite and are taken as its upper boundary.

Upon the \(H_0\) suite, without noticeable angular unconformity, lie productive deposits, assigned according to the new stratigraphic scheme of Kuzbass to the Anzher suite \((H_1)\) of Lower Permian age \((P_1)\).

The Anzher suite is divided by Prokopyevsk geologists (1) into three subsuites: lower \((H_1^1)\), middle \((H_1^2)\), and upper \((H_1^3)\).

Lower subsuite \((H_1^1)\). The top of the Bezymyanny seam is conventionally taken as the upper boundary of this subsuite (Appendix I). In the eastern part of the district, directly upon the conglomerate of the \(H_0\) suite lies a greenish fine-grained sandstone 40 m thick. Above it occur sandy-clayey

shales with a thickness of 20 m. Higher up, beginning with coal seam No. 11, there is developed a 40–45 m thick unit of grayish sandstone, passing in the lower horizons into sandy argillite and argillite. The sandstone is overlain by a unit of clayey rocks about 160 m thick, represented mainly by sandy banded argillites and argillites with ten coal seams (Nos. 1–10, counting from the top). This unit of clayey rocks is distinguished by local workers under the name of the productive member of subformation \(H_1^1\). Above this clayey unit lies a unit 70 m thick, represented by frequent alternation of sandstone, sandy banded argillite, and argillite. In it there occur thin (0.10–0.15 m) interbeds of coal and carbonaceous argillite.

In the western part of the district, within the lower subformation there are two productive horizons or, adhering to local terminology, two productive members, which are separated by a coal-barren horizon 30–40 m thick, composed of sandstones and sandy banded argillites. The lower productive member is separated from the unit of green sandstones lying on the conglomerate of formation \(H_0\) by a horizon of sandy-clayey rocks of small thickness. It is composed of sandy-clayey banded argillites, argillites, and three coal seams (Nos. 7, 8, 9). Its thickness is determined as 75–90 m. The upper productive member is composed of the same rocks as the lower one, but it contains six coal seams (Nos. 1–6). Its thickness is determined as 100 m.

The average normal thickness of the lower subformation in the eastern part of the district is 331 m, and in the western part 315 m.

The middle subformation (\(H_1^2\)) begins at the floor of the Bezymyanny seam (Appendix I). Its upper boundary is taken to be the conglomerate lying in the roof of the Kharakterny seam.

The lithological composition of this subformation in the eastern part of the district differs somewhat from its lithological composition in the western part. Thus, in the eastern part, directly above the Bezymyanny seam there is developed a 40–55 m thick unit of sandy banded argillites, replaced upward by fine-grained sandstone. The latter forms the floor of the Moshchnyi seam. Above the Moshchnyi seam lies a unit 55–65 m thick, composed of sandstones and sandy banded argillites. It contains one coal seam—the I Prokopyevsky. Above this unit, within a thickness of 30–35 m, there is developed a sandy-clayey horizon with a group of three coal seams close to one another: Prokopyevsky, Lutuginsky, and Gorely. Above the Gorely seam comes a grayish fine-grained sandstone 30–50 m thick. In the uppermost horizons, directly in the floor of the Kharakterny seam, this sandstone passes into sandy argillite. The roof of the Kharakterny seam is a conglomerate, a more or less persistent marker horizon of the Anzherskaya formation of the Prokopyevsk district.

In the western part of the district the Kharakterny seam is locally absent, and then the upper boundary of the subformation comes close to the Gorely seam, being separated from it by a sandstone unit 20–30 m thick. In these cases the conglomerate horizon splits into several interbeds of varying thickness enclosed in sandstone having a total thickness of up to 25 m. Between the Gorely and Moshchnyi seams there is developed a unit 100–120 m thick, composed of sandstones, sometimes with interbeds of conglomerate-like sandstone, sandy banded argillite, and argillite. This unit is underlain by the Prokopyevsky seam, consisting sometimes of one coal band and sometimes of two or more. The Lutuginsky seam is absent here.

The average normal thickness of the subformation in the east of the district is 225 m, and in the west 202 m.

The upper sub-suite \((H_1^3)\) is bounded above in places by seam VII Internal and, in places, where the latter is absent, by seam VI Internal.

The lithological composition of this sub-suite is more constant. Thus, in the eastern part of the area, a light-gray sandstone 20–30 m thick overlies the conglomerate of the Kharakternyi seam. Upward it gradually changes into sandy argillite 10–15 m thick. Above follows a sequence of sandy argillites and sandstones—75–80 m. It begins with seam I Internal and contains, in addition, seams II, III, and IV Internal. Above seam IV Internal there is developed a sequence about 45–50 m thick, composed predominantly of sandy banded argillite and argillite. The latter is overlain by sandy-clayey rocks 30 m thick. They are represented by sandstones, sandy banded argillites with three coal seams—V, VI, and VII Internal. Seams V and VII Internal in the eastern part of the area are sometimes absent.

In the western part of the area the lithological composition of the sub-suite is almost the same as in the east, but here the thickness of some horizons changes somewhat. Thus, the thickness of the sequence developed between seams IV and V Internal is here only 25–35 m, while between seams I and IV Internal it is somewhat greater than in the east and reaches 85 m.

The average normal thickness of sub-suite \(H_1^3\) in the east of the area is 195 m, and in the west—178 m.

Above seam VII Internal, conformably with the deposits of suite \(H_1\), lie deposits of the coal-barren suite \((H_2)\), assigned, according to the new stratigraphic scheme, to the Middle Permian \((P_2)\). This suite is composed of interbedded sandstones, banded argillites, and argillites. All these deposits have a dirty greenish-yellowish color. Among them are developed interbeds, and sometimes lenses, of ferruginous argillites and partings of coal of noncommercial thickness.

Thus, summarizing the stratigraphic data on the Anzherka suite, we see that the order of bedding, the lithological composition, and its thickness within the Prokop’evsk area vary. This is apparently explained by the fact that during the epoch of formation of the Anzherka suite different facial conditions existed in different parts of the area.

The coal-bearing deposits of the Prokop’evsk area are gathered into a series of compressed synclinal and anticlinal folds of NW strike, with an average distance between the axial planes of anticlines or synclines of 1500 m (Appendix 1).

The limbs of the folds have a steep dip. The angle of dip, both along the strike of the limb of one fold and in the limbs of different folds, varies within the range from \(32^\circ\) to \(85^\circ\), averaging \(60\)—\(65^\circ\).

The axes of the folds plunge more often to the north. The angle of plunge of the fold axes varies within rather wide limits. Thus, for example, along the axis of the first syncline it varies from \(3^\circ\) to \(20^\circ\), and along the axis of the fifth syncline its fluctuations lie within \(12\)—\(22^\circ\). On average, however, the angle of plunge of the fold axes does not exceed \(14^\circ\).

In addition to these principal folds of the first order, P. F. Krasnikov (6), who studied the mine tectonics of the eastern part of the area, recorded on the western limb of the fifth syncline additional foldlets of the second order, of strike conformable with the principal folds. These foldlets, in his opinion, formed as a result of an independent plicative process that occurred later than the formation of the principal folds of the area.

All these plicative dislocations are strongly complicated by disjunctive disturbances, more often of the type of longitudinal thrust faults, with displacement reaching up to

800 and more meters. The dip of the planes of the latter disturbances is mainly western, which is fully explained by pressure from the Salair side. The angle of dip is 80–85°.

In the district there are observed thrusts and diagonal-transverse faults, but less frequently than the former, and they usually belong to the category of minor disturbances.

The coals of the Prokopyevsk district, by chemical composition and coking character, are subdivided into three groups. The coals of the Inner seams are coking coals, while the coals of the seams of the two lower sub-suites, with the exception of the Moshchnyi and Bezymyannyi seams, are semi-coking. The coals of the Moshchnyi and Bezymyannyi seams go directly to the blast furnace as raw blast-furnace fuel.

The proximate analysis of all mined coal seams is given in Table 1 (1; 7).

Table 1

Proximate analysis of the coals of the Prokopyevsk district.

Name of seam	Seam thickness	Moisture \(W^p\)	Moisture \(W^z\)	Ash \(A^c\)	Volatiles \(V^c\)	Volatiles \(V^z\)	Sulfur \(S\)	Calorific value on combustible mass	Coke character
Inner VI	5–6	3.70	0.53	7.58	22.58	24.46	0.49	8582	Fused, moderately dense, swollen, silvery
Inner IV	"	4.23	0.53	8.67	24.73	27.08	0.43	8552	"
Inner III	2	—	0.61	5.94	—	21.34	0.38	8614	"
Inner II	5–6	4.17	0.64	5.09	20.27	21.36	0.59	8575	"
Inner I	"	4.8	0.58	9.26	23.68	26.09	0.64	8528	"
Kharakternyi	Ц.ш	2.96	0.69	8.12	16.11	—	—	—	Partly fused, dull
Gorelyi	2	2.31	0.85	4.42	17.68	18.50	0.38	—	Sintered, hard
Lutuginsky	"	4.87	1.37	5.17	16.00	16.80	0.45	—	Fused, silvery
Prokopyevsky	"	2.34	0.36	7.30	15.78	17.9	—	—	Partly fused, dull
Moshchnyi	Ц.ш	3.91	1.91	3.44	13.58	—	—	—	Not sintered
Bezymyannyi	"	5.63	2.82	6.66	14.74	—	—	—	"
Spornyi No. 1	"	—	0.60	11.67	16.90	19.17	0.73	8702	Fused, moderately swollen, silvery
Dvoinoi No. 3	"	—	0.93	6.86	15.79	16.95	0.49	8652	Fused, silvery
Udarnyi No. 4	"	—	0.80	5.16	16.31	17.20	0.48	8588	Partly fused, hard
Sadovyi No. 5	"	—	1.02	5.92	14.61	15.53	0.60	8686	"
Pioner No. 6	"	—	0.92	8.53	14.27	15.60	0.55	8604	Weakly sintered
Yungor No. 7	"	—	1.10	6.45	13.37	14.29	0.60	8511	"
Uglovoi No. 8	"	—	1.10	6.07	14.70	15.01	0.92	8640	Sintered, hard

From this table it is evident that the coals of the seams of the Inner group are always characterized by a fused, moderately dense, medium-swollen coke button. The volatile content on an absolutely dry fuel basis in them ranges from 20 to 24%, although on the combustible mass these fluctuations are wider (21–27%), which is due, as is evident from the table, to the different ash content in them, which ranges from 5 to 9%. The sulfur content is insignificant and on average does not exceed 0.5%. The phosphorus content in them is likewise insignificant—0.015–0.06%. The calorific value on combustible mass is 8600 calories.

The semi-coking coals give a yield of volatile substances on an absolutely dry fuel basis of from 14 to 17%; the coke button is sintered, partly fused. The ash content in them is small and on average equals 8%. The calorific value on combustible mass is 8700 calories.

Dome angles of the Moshchnyi and Bezymyannyi seams are characterized by a low yield of volatile matter and a non-caking coke button. Thus, in the Moshchnyi seam the content of volatile matter on an absolutely dry fuel is 13%, and in the Bezymyannyi seam—14%. The ash content in them is insignificant, especially in the Moshchnyi seam (3.44%).

Recent chemical studies of the coals have shown that the technical properties of the coals are not maintained over the entire area of the district. Thus, according to Engineer S. Zolotov (8), the properties of coking coals vary both in the direction from west to east and from north to south (Table 2).

Table 2

Name of mines	Name of mines	Technical analysis	Technical analysis	Technical analysis	Technical analysis	Seam measurements	Seam measurements	Caking capacity according to Grigor'ev
From west to east	From north to south	Laboratory moisture, \(W^n\)	Ash on dry \(A^c\)	Volatile matter on combustible, \(V^2\)	Calorific value on combustible	Shrinkage in mm	Thickness of plastic layer	Caking capacity according to Grigor'ev
No. 7		1.49	10.30	28.01	—	29	16.25	4
No. 6		0.98	10.78	24.42	8490	24.8	16	4
No. 5		1.48	10.30	20.90	8415	32	9.25	5.6
Koksovaya		1.05	8.75	19.10	8497	24	13.9	4.25
No. 2		1.22	7.58	16.55	8522	27	10.8	5
Central adit		1.28	9.48	18.00	8467	23.5	8	5.25

II. General data on seam VI Vnutrennii. Sampling and work methodology.

Seam VI Vnutrennii is the uppermost workable coal seam of the upper sub-suite of the productive deposits of the Prokop'evsk district.

Its thickness, according to drilling data (1), fluctuates within broad limits in different parts of the district. Thus, in the western part it ranges from 0.24 m to 3.72 m, and in the eastern part—from 1.80 m to 3.60 m. But since in the operating workings, which already cover considerable areas in the district, the seam thickness is maintained on average at 3 m, with small deviations in either direction, the cited fluctuations in seam thickness may be attributed to the inaccuracy of prospecting work.

In its chemical characteristics, the coal of seam VI Vnutrennii is a typical coking coal with an average content of volatile matter on air-dry fuel of 23–24%. The ash content ranges from 5 to 9%. The crucible coke is well fused, medium-swollen, silvery. However, its properties change greatly in the direction from south to north. Thus, according to the technical analysis of cores and sludges (1), in the south of the district, between the Krutye and Srednie Topki logs, it contains 23% volatile matter on combustible mass. Farther north the content of volatile matter increases, and at the IV exploration line the content of volatile matter on combustible mass already reaches 34.98%, while the caking capacity also changes in the direction of deterioration. In addition, studies by Engineer S. Zolotov (8) showed that its properties are not maintained in the direction from west to east either. In this direction there is an almost regular decrease in the yield of volatile matter and a decrease in the thickness of the plastic layer (Table 3).

Table 3

Indicators	Mine No. 7	Mine No. 6	Mine No. 5	Koksovaya Mine	Central adit
Thickness of plastic layer	23.0	24.0	20.0	18.0	12.0
Yield of volatile matter on combustible mass	27.51	24.26	24.55	21.45	17.23

At the present time the seam is being developed by almost all the principal extraction workings of the Prokopyevsk Mine Administration, and therefore it is the most accessible for study. In addition, the desirability of studying it is also due to the fact that, with a comparatively small thickness of 3 m, it characterizes an entire group of the most valuable coking coals of the Inner seams.

However, despite the extensive exploitation of the seam, we did not succeed in sampling it at even two points along the strike of a single fold. Mine No. 7 and the Rukhimovich Mine (Zimenka), which work the seam in the western limb of the third syncline and are separated from one another along the strike of the limb of the fold by 6–7 km, could not be used by us because the seam in the Rukhimovich Mine proved to be strongly tectonically disturbed and entirely unsuitable for the purposes of our study.

For this reason, the three points of the seam designated for investigation had to be selected in extraction workings arranged in a latitudinal direction, namely: in the west of the district in Mine No. 7, in the center of the district in Mine No. 5, and in the east of the district in Adit No. 11 (a continuation of the Central Adit).

At each selected point one seam sample was taken from the seam in the form of hand specimens, consecutively making up a column 20 × 20 cm in size through the entire thickness of the seam. In all, three samples were taken in this way, arranged in the following order.

Sample No. 1 was taken in Mine No. 7, located in the western part of the district, 1.5–2 km to the WSW of Mine No. 5–6. This mine is new. It entered partial operation in the spring of 1934. It is at present working the Inner seams of the western limb of the third syncline.

The part of the syncline opened by the mine has simple tectonics. The beds dip monoclinally to the east at an angle of 75–85° without rupture of continuity and without additional bends or crumpling.

Sampling of the seam was carried out in the northern part of the mine, in the face of the main drift, 157 m south of the northern crosscut. The thickness of the seam at the place where the sample was taken is 3 m. The dip angle is 80°.

It should be noted that at this point we were unable to take a column sample through the entire thickness of the seam, because the middle part of the seam, 0.32 m thick and consisting of broad-banded coal, is not very stable owing to extensive fracturing. Thus, the column sample did not equal the full thickness of the seam, but 2.68 m.

Sample No. 2 was taken in Mine No. 5. This mine is located in the western part of the district, 0.5 km west of the Tomsk Railway, and is part of Mine No. 5–6 named after Comrade Voroshilov. Mine No. 5–6 works the southern and central part of the eastern limb of the third syncline, complicated by a large longitudinal overthrust with an amplitude of 1000–1300 m. The hanging wall of the overthrust, or the southern part of the limb of the third syncline, is worked by Mine No. 6, from seam VI Inner to the Characteristic seam. Mine No. 5 works the footwall of the overthrust, or the central part of the third syncline, from seam VI Inner to the Powerful seam inclusive.

Sampling of the seam was carried out in the southern part of the mine, in the face of the first parallel drift, 70 m south of survey point No. 2364. The thickness of the seam at the place where the sample was taken is 3.15 m. The dip angle is 70°.

Sample No. 3 was taken in Adit No. 11, which is a continuation of the Central Adit. These adits are located in the eastern part of the district on the left bank of the Aba River, 3.5 km south of the Usyaty station of the Tomsk Railway and on

at the same distance east of mine No. 7. They work the repeating seams of the upper and middle series of the fifth and sixth synclines, with gallery No. 11 working the eastern limb of the sixth syncline. The hinge of the sixth syncline, as well as its western limb, is strongly disturbed by a whole series of disjunctive dislocations of the thrust-fault type with small amplitudes, while its eastern limb dips calmly to the west at an angle of 70–80°.

Sampling of the seam was carried out in the northern part of the gallery, at the face of the main crosscut, at a distance of 12.3 m from oven No. 24. The thickness of the seam at the sampling site is 3.30 m. The dip angle is 71°.

Thus, the investigation of Inner seam VI was conducted on three seam sample-columns taken in three working excavations situated along the strike.

Under laboratory conditions all the samples obtained were subjected to a thorough petrographic study, and the petrographic observations were checked by the simplest chemical analyses (technical and elementary).

The composition of the seam was first studied macroscopically. For this purpose the pieces of each sample were taken out of the packaging, carefully cleaned of packing material and dust, and then laid out in sequence on a table in the form of a seam column. Then one of the long sides of each seam column was cleaned of possibly oxidized coal by splitting off a coal layer 1.5–2 cm thick. After this, on the cleaned side of each seam column, a careful examination was made of the structure and composition of the seam. In this examination, samples were selected from all the coal layers that had been identified; these samples were then compared and, on the basis of various macropetrographic features (luster, structure, composition, etc.), were divided into coal varieties. The most typical samples of the distinguished coal varieties were retained as standards. Such standards of coal varieties were compiled for each sample separately.

After thus studying the macropetrographic composition of the seam, we proceeded to the preparation of detailed petrographic sections for each seam column. For this purpose, three lines were drawn in colored pencil on the cleaned side of the column, at a distance of 5 cm from one another. Since the width of the seam columns was 20 cm, these lines, one of which was drawn along the middle of the column, divided it into four equal parts. After this, beginning from the floor of the seam, each petrographically individual layer was measured in millimeters along all three lines and plotted on millimeter paper in its natural form, i.e., with its true dimensions and with all details of its occurrence in the seam (bends, character of wedging-out, and so forth), so that as a result the graph gave a true copy of the structure and composition of the seam at the point studied. In addition to recording the composition and structure of the seam, all the mentioned coal layers, as well as the layers of barren rock, were studied with respect to their physical properties. This was done in stratigraphic order and recorded in the form of a log adopted for the description of cores.

Together with the preparation of petrographic sections from the seam columns, samples of coal varieties were selected for microscopic study and, in addition, samples for chemical analyses. The samples and specimens were selected from the same layers; moreover, from the varieties predominating in the seam, the samples and specimens were selected from layers having a thickness of 30 mm and more, but always from the lower, middle, and upper horizons of the seam, if they were observed there. From the rare varieties of the seam, samples and specimens were selected from all layers having a thickness of 5 mm and more.

Microscopic examination was carried out on polished sections. In doing so, in addition to describing the microstructure of the varieties of coal and the character of the ingredients composing them, a quantitative count of the microcomposition was made along two traverses with the aid of a linear ocular micrometer.

Chemical investigations were conducted using proximate and ultimate analyses. All varieties of coal from each sample separately were subjected to proximate analysis, while only vitrite and the first variety of coal were subjected to ultimate analysis.

After the microscopic and chemical investigations had been carried out, the composition of the seam was reviewed once more, and its subdivision into coal varieties was corrected, taking into account the microscopic data and chemical analyses.

In addition to the investigations indicated, we made an attempt at maceration of the first variety of coal. We carried out the maceration by the Schulze method (12), but with certain modifications. We took 1 gram of finely ground coal, placed it in a chemical beaker, mixed it with 2 g of Berthollet’s salt, and poured in 20 cm³ of concentrated nitric acid. The beaker with the solution thus obtained was heated on an electric hot plate until brown vapors were evolved and until the solution turned brown. After this the beaker was allowed to cool for 20–30 minutes, and then water was added to it in an amount equal to the contents of the beaker. In this process humic substances precipitated from the solution in the form of a flocculent mass of brownish-brown color, readily soluble in $KOH$. We dissolved the humic substances in a centrifuge, adding alkali twice. After this, in the same centrifuge, the solution was washed with water until it became completely transparent.

As a result of this method of maceration, from the coal of the first variety of seam VI Inner, described below, the following were isolated: fusainized cellular tissue, spores, and cuticles.

We shall now proceed to set forth the composition and structure of the seam, first for each individual sample. This will enable us subsequently to trace how its petrographic composition changes along the direction we selected.

III. Special Part.

In microscopic examination, in the composition of the coal we distinguish durite, clarite, vitrite, xylovitrite, xylite, and fusite. Vitrite and fusite are the simplest ingredients, which are readily recognized both macroscopically and microscopically, and therefore they require no special explanation. All the other ingredients distinguished by us are recognized only under the microscope. Moreover, these ingredients are not always understood in the same way in the existing literature on coal petrography. We therefore consider it necessary to explain which microscopic coal formations observed in polished sections we assign to one or another of the ingredients distinguished by us.

To durite we assign all microscopic coal formations (bands and lenses) consisting of a basic gray structureless mass, cementing formed bodies (spores, sclerotia, fragments of cuticle, resin bodies, fragments of xylite and fusite tissues, and others). In the coal of the seam studied, in the basic structureless durite mass, in most cases, there are inclusions of small fragments of xylite and fusite tissues and indeterminate organic forma-

…of rounded shape and, in rare cases, fragments of the cuticle and shells of microspores. In addition, the saturation of the principal structureless mass of durite with shaped formations varies: at times it is strongly saturated with them, at times weakly. In the case when the principal mass of the durite is strongly saturated with shaped formations, it is observed in the form of small islands of various shapes among a mass of often chaotically arranged shaped formations and has a bluish-gray color. In the case of weak saturation of it with shaped formations, it appears in the form of broad bands of gray or pale-gray coloration, in which shaped formations are rarely located.

By clarite we mean such formations as consist exclusively of a principal structureless mass of gray color, including long, hair-like cutinized fibers. These fibers are arranged either in the form of slightly curved parallel lines, which divide the structureless mass into almost equal parallel bands, or in the form of correspondingly increasing lamellar folds, forming the structure of lignite.

By xylovitrinite are meant bands and lenses possessing a yellowish-pale-gray color, with a structureless or weakly manifesting, sparse, punctate-structured surface and low relief. Structureless xylovitrinite differs from vitrite in that it does not have the transverse fissuring characteristic of the latter, and always occurs in the form of continuous bands or lenses. In addition, they are easily distinguished by color. Structureless xylovitrinite has a pale-yellow coloration, whereas vitrite is gray or pale gray.

By xylite are meant bands and lenses of yellow or pale-yellow color, with a punctate or dash-like structure. In addition, we also include here formations occurring as accumulations of elongated narrow ribbons and angular fragments of plant tissue. This xylite possesses a yellow color, high relief, and a sparse fine-cellular structure.

I. Description of the coal varieties.

At all the points studied, seam VI Inner is composed of banded coal, which, on the basis of varying degrees of luster and the different character of its composition, was subdivided by us into eight varieties. In doing so, vitrite bands and fusite lenses, clearly distinguished macroscopically and having a thickness of more than 2 mm, were separated into independent groups.

Of the eight varieties of coal composing the seam, only six varieties are of general occurrence. Two varieties of coal—V and VII—are observed in isolated cases, namely: variety V is observed only in sample No. 2, and VII only in sample No. 1. Moreover, the common coal varieties in each sample studied have distinctive petrographic as well as chemical characteristics.

Sample No. 1 is composed of the following coal varieties: I, II, III, IV, VI, VII, and VIII. These varieties are characterized as follows.

I variety of coal. Macroscopically, a pitch-lustrous coal of black color, with a streaky, in places banded composition. The fracture is flat. The streak is black with a slight brownish tint. The coal is rather weak; under a light blow it breaks up into pieces of shell-like form.

Microscopically it is composed essentially of durite and vitrite, with subordinate occurrence of xylovitrinite and xylite and very rare inclusions of fusite (Table 4).

Durite in polished sections is observed as broad bands and is characterized by a weakly saturated, shaped groundmass. The latter consists predominantly of small yellow, low-relief formations of unclear nature, small fragments of cuticle, and brownish-gray flattened shells of microspores. Rarely observed here are accumulations of rounded-angular and oval bodies of unclear nature. These bodies have a pale-gray color and a smooth or wavy surface (Table I, Fig. 3). Sometimes the duritic bands present the appearance, as it were, of plant tissue split into thin fibers, the spaces between which are filled with the main structureless mass (Table I, Fig. 1). Tracing such bands along their length, one can observe how some of them, gradually toward one end or the other, become cleaner, i.e., the plant fibers become discontinuous and thin, and in places disappear completely, merging into a single whole with the main structureless mass (Table I, Fig. 2).

Vitrinite in polished sections of this coal variety occurs in the form of large lenses, branching at the ends into thin bands, which then again merge and form one continuous mass. It differs from the surrounding main structureless duritic mass by a more delicate pale-gray color and clearly expressed transverse cracks, which die out at the boundaries with the duritic bands.

Xylovitrinite forms either broad bands or small lenticles. It is characterized by a yellowish-white color, low relief, and an almost smooth, structureless surface.

Xylite gives long, thin lenticles and separate fragments of irregular form. Its distinctive features are: a delicate yellow color, rather high relief, and a sparse dotted structure. The xylite lenticles in most cases border on lenticles of xylovitrinite and in places merge with the latter without a noticeable boundary. In addition, xylite in places gradually passes into finely cellular fusite.

An interesting fact for the Prokopyevsk coals in general, and in particular for the variety described, is the presence here of clarite (Table 1, Fig. 5). Clarite occurs as rather narrow bands, in places as separate spots, and is characterized by a pale-gray structureless groundmass, dissected by thin hair-like cutinized fibers into nearly equal parallel bands.

Of the mineral inclusions in polished sections of this variety, there are rarely scattered, extremely fine grains of pyrite and very rare rounded specks of yellow-gray color, which effervesce under the action of hydrochloric acid.

II coal variety. Macroscopically, a semi-bright coal of grayish-black color, with a weakly expressed fine-streaked composition. The fracture is flat. The streak is black. There is fine, dying-out fissuring running perpendicular to the bedding.

Microscopically it consists chiefly of durite, with vitrinite, xylovitrinite, xylite, and fusite in subordinate positions (Table 4).

Durite, as in the coal of the first variety, occurs as broad bands. It is characterized by a pale-gray main structureless mass, weakly saturated with shaped formations. The latter consist mainly of small fragments of xylitic tissue and rarely scattered formations characterized by yellow color, high relief, and angular-notched edges. The nature of these formations is unclear, but apparently they belong to fragments of destroyed cellular plant tissue.

Vitrinite occurs as broad bands, which possess a pale color—

with a completely clean structureless surface. Xylite and xylovitrinite possess the same properties as in coal of the first variety.

The content of fusite in this variety increases to 6% (Table 4). It occurs more often as short but broad lenses and has a fine-cellular structure. Very rarely, small areas of reworked fusite with an arcuate and stellate structure are observed.

III variety of coal. Macroscopically, this is an almost dull coal of gray color, indistinctly banded, of almost massive composition. The fracture is uneven. The streak is black. In its composition there are rare, scattered, very small lenses of hard fusite and very rare threadlike cords and needles of vitrite.

Microscopically, coal of the III variety consists mainly of durite and xylite, with vitrite, xylovitrinite, and fusite in a subordinate position (Table 4).

The durite of this variety is characterized by a strong saturation with formed constituents (Table 1, Fig. 4). The formed constituents consist essentially of small, indeterminate organic formations of a bluish-brownish-gray color (lilac). These formations are arranged as elongated bodies with irregular outlines. In addition, among the formed constituents there are observed here small fragments of xylite tissue, fragments of hair cuticles, and also yellow rounded bodies of indeterminate nature. The latter have a parallel-lineate or porous-serrate structure.

Vitrite here amounts to only 5% (Table 4). It occurs as small elongated lenses uniformly scattered throughout the whole mass of coal. In places, vitrite lenses form a border around xylovitrinite lenses, which differ from vitrite by their lighter coloration and slightly wavy-rough surface.

Xylite occurs as broad and long lenses and as separate fragments scattered throughout the coal. As in the preceding varieties, it is characterized by a pale-yellow color, punctate structure, and high relief.

In addition to the indicated ingredients, rare, almost solitary, large lens-like formations of fusite with a fine-cellular structure are observed here.

IV variety. Macroscopically, this is dull gray coal with a slight glossy sheen, of dense, almost homogeneous composition. The fracture is irregularly angular. The streak is grayish-black. On careful examination one may observe rare inclusions of the thinnest needles of fusite.

Microscopically, it consists of randomly and densely scattered small fragments and lenses of xylite and fusite among the main durite mass. In addition, small and irregular areas of xylovitrinite and very rare, extremely thin needles of vitrite are observed here.

Among the mineral inclusions, pyrite is observed in the form of scattered small angular pieces, as well as cords filling cracks in the coal.

VI variety of coal. Macroscopically, this is dull gray-black coal, of dense homogeneous composition. The fracture is coarse, angular-uneven. The streak is grayish-black.

Microscopically, it consists of irregularly arranged small fragments of xylite and fusite amid the main structureless mass cementing them, of bluish-gray color, observed in the form of small round and elongated spots.

VII variety of coal. Macroscopically, a matte, dense, homogeneous coal. This coal is similar to coal of variety VI and differs from it only in having a flat-conchoidal fracture and a noticeably higher specific gravity.

Microscopically, it consists mainly of a yellow, structureless organic mass of the xylite type, penetrated by frequent inclusions of clayey formations of rounded-spotted form. Rarely, scattered fragments of fusite and indefinite rounded formations are observed among this mass.

VIII variety of coal. Macroscopically, a matte coal of dark-gray color, with a granular structure. The granularity is due to frequent and uniformly scattered small grains of vitrite in the main dark-gray, sometimes brownish, strongly mineralized mass. Cracks in this coal are usually filled with round grains of marcasite of greenish-yellow color. These grains form close accumulations in the form of a sparkling, lumpy film.

Microscopically, it consists of an accumulation of shapeless fragments of xylite and fusite, as well as large round spots of a gray structureless mass. All these organic formations are penetrated by rounded and elongated mineral inclusions (Table III, Fig. 6). The mineral inclusions have a brownish-gray color and a rough, as if porous, surface. Under the action of hydrochloric acid they effervesce vigorously, which gives grounds for assigning them to calcite formations.

Let us note that in some thin sections of this variety of coal areas of clarite are observed (Table I, Fig. 6).

Thus, varieties I–VIII of coal, composing seam VI Inner at point No. 1, macroscopically are arranged in the order of decreasing degree of luster and increasing homogeneity of composition, although in general they have a dense structure and a weakly expressed differentiation of macropetrographic composition.

Corresponding to the change in luster, both their micropetrographic and technical composition change (Table 4).

Table 4

Name of coal varieties	Durite	Vitrite	Clarite	Xylovitrite	Xylite	Fusite	Structureless mass	Shaped formations	\(W^a\)	\(A^a\)	\(V^a\)	\(A^c\)	\(V^c\)	\(V^g\)	Character of the coke button
I variety	59	24	2	6	6	2	90	10	1,00	2,48	27,27	2,50	27,50	28,25	Fused, swollen, with a sooty top
II variety	68	11	—	10	5	6	88	12	1,07	2,67	25,69	2,69	25,97	26,68	Fused, steel-gray in color
III variety	71	5	—	6	15	3	87	13	0,72	2,91	25,38	2,93	25,62	26,39	Sintered, with a fused top, steel-gray in color
IV variety	56	traces	—	3	13	27	81	19	0,93	6,43	23,23	6,49	23,44	25,07	Sintered, with a fused top, steel-gray in color
VI variety	55	traces	—	6	32	6	64	36	0,91	8,07	19,06	8,14	19,23	20,94	Sintered, black
VII variety	—	—	—	—	—	—	—	—	0,89	33,54	13,51	33,84	13,63	20,57	Granular-sintered, black
VIII variety	—	—	—	—	—	—	—	—	1,02	16,47	27,45	16,64	27,73	33,27	Fused, moderately swollen, steel-gray in color

From this table it is evident that the content of vitrite and of the structureless mass of durite decreases almost regularly from the first variety to the sixth. In the same direction the yield of volatiles decreases and the ash content increases, and the character of the caking capacity also changes. The exception to this rule is the VIII variety of coal. This variety, both in petrographic habitus and in chemical composition, stands apart from the almost regularly changing series of the remaining varieties.

Sample No. 2. In the composition of this sample, the I, II, III, IV, V, VI, and VIII varieties of coal are observed, characterized as follows.

I variety of coal. Macroscopically, a lustrous coal of black color, of thin-banded, in places striated composition. The fracture is flat, with barely noticeable unevenness on the fracture surface. The streak is black and lustrous. Vertical cleat cracks are clearly expressed, running in two mutually perpendicular planes; moreover, in one plane they are strongly developed, while in the other they are very weak.

Microscopically it is composed mainly of durite and vitrite, with a small amount of xylovitrite and xylite (Table 5).

Durite gives broad bands. Its pale-gray main structureless mass includes frequent pale-yellow, weakly relief-bearing structureless lenses, in shape resembling the lilac-colored bodies observed in the I variety of coal of sample No. 1. Rounded bodies of obscure nature are rarely observed here. These bodies have a yellow color, a porous-spongy structure in the middle part, and a rather thick peripheral rim. They are situated in the durite either singly and scattered, or in accumulations (Table II, Fig. 2).

In addition, here, as in the coal of the I variety of sample No. 1, there are observed areas of durite representing plant tissue split into fine fibers and cemented by the pale-gray main structureless mass of durite. But here this picture appears more distinctly than there (Table II, Fig. 1).

Vitrite is identical with the main structureless mass of durite. In thin sections it occurs in the form of frequent thin bands branching at the ends and small lenses. Bands of xylovitrite are rarely observed here, characterized by a pale-gray color and a punctate, and in places discontinuously dash-like, structure. Very rarely, lenses of xylite and thin fragments of fusite occur in the composition of this variety. The latter have the appearance of elongated thin chains with beautifully expressed rounded-oval cell openings.

II variety of coal. Macroscopically, a semilustrous coal of dark-gray color, of finely striated composition. The fracture is uneven, finely hummocky. The streak is black. Cleat is vertical, but appears weakly.

Microscopically it consists predominantly of durite, with subordinate xylite, vitrite, xylovitrite, and fusite (Table 5).

Durite occurs in broad bands and is characterized by a pale-gray main structureless mass, either very weakly or more or less strongly saturated with organized elements. In the first case, the organized elements of durite consist chiefly of pale-yellow, structureless, weakly relief-bearing small lenses of obscure nature and rounded bodies having a pale-gray color, a smooth or slightly wrinkled surface, and high relief. In the second case, a large quantity of small fragments of xylite and fusite tissues is admixed with the indicated organized elements of durite.

Vitrite is observed in the form of rare, elongated lenses sharply tapering at the ends. Also rarely observed here are lenses of xylovit-

rite and fusite. The latter have a well-preserved, thin-walled, finely cellular structure. More often observed here is xylite, which occurs in polished sections sometimes in the form of thin lenticles with a beautifully expressed punctate structure, sometimes in the form of broad, short bands which at their ends branch whimsically into separate fine fibers, either breaking off or merging with the surrounding structureless mass of durite (Table II, fig. 3).

III variety of coal. Macroscopically, a semi-matte coal of grayish-black color, with a clearly banded composition. The fracture is uneven, the streak black. There are frequent, fine, discontinuous cracks situated perpendicular to the bedding.

Microscopically it consists of an alternation of broad bands of durite with lenticles of xylite and rare bands of xylovitrinite and vitrite.

Durite is characterized by a bluish-gray, fundamental, structureless mass, strongly saturated with small fragments of xylite, fusite, and rare rounded bodies. The latter possess a yellow color, high relief, and a parallel-streaked surface.

Vitrite occurs in polished sections as frequent thin bands, splitting at the ends into the finest fibers, which gradually merge with the structureless mass of durite. Xylovitrinite lies either in the form of broken bands or in the form of small, blunt-ending lenticles. Xylite gives interesting formations here. It lies in broad areas, which consist of a fundamental yellow mass with a wavy-rough surface. This mass includes separate fragments of plant tissue, arranged sometimes in the form of irregular pieces with sharply toothed edges and a rare cellular structure, sometimes in the form of thin ribbon-like bands (Table II, fig. 6). The latter split at the ends into a series of fine fibers, which then merge with the enclosing mass, as though dissolving in it.

Among the mineral inclusions, pyrite is observed in the form of sparsely scattered, very small angular pieces.

IV variety of coal. Macroscopically—a matte coal of gray color, with a faintly streaked composition. The fracture is uneven—finely hummocky. The streak is black. In its composition there are inclusions of the smallest lenticles of fusinite and rare needles of vitrite. A rare, very fine fissuring is observed, running at an angle of 75° to the bedding.

Microscopically it is composed essentially of durite, fusite, and xylite, with a small content of vitrite and xylovitrinite (Table 5). In polished sections all these ingredients are arranged without any clear regularity. The main field of the polished section is occupied by durite, in which the fundamental structureless mass is strongly saturated with all sorts of shaped formations. The latter are composed of rounded bodies of unclear nature, fragments of xylovitrinite and fusite tissues, and oval formations of gray color (Table II, fig. 4). The latter are structureless and, in coloration, stand close to vitrite and to the structureless mass of durite, but their more or less high relief and their form compel one to attribute them to some other organic formations of as yet unclear nature.

Fusite and xylite, as well as vitrite and xylovitrinite, occur as separate lenticles scattered in the durite mass. In places fusite is observed in the form of broad bands with a distinct, now flattened-elongated cellular, now spongy structure (Table III, fig. 5).

Among the mineral inclusions there is pyrite, which is observed in the form of the smallest angular pieces.

V variety of coal. Macroscopically, a matte coal of black color, of finely banded composition. The fracture is uneven. The streak is black. In its composition

it contains much fusite, which is arranged in the form of thin irregular cords and small lenses. The latter are often bordered by a thin rim of semilustrous or lustrous coal. On horizontal fractures, fusite is observed as broad, shapeless spots, in which silky rectangular plates stand out.

Microscopically it consists essentially of durite and fusite, with subordinate ksilite and vitrite.

Durite occurs in broad bands and is characterized by a more or less strong saturation with structural and formed elements, among which first place belongs to fragments of ksilite and fusite. Very rarely, rounded gray bodies with a smooth or indistinctly striated surface are observed in the durite, as well as thin, slightly wavy fragments of pale-yellow color, belonging, in all probability, likewise to elements of plant tissue.

Fusite is arranged in broad irregular formations, sometimes with blurred outlines (Table II, Fig. 5). Its structure is more often finely cellular and more rarely coarsely cellular. Very rarely there are areas of broken fusite with an arc structure.

Ksilite occurs as thin, strongly elongated lenses. Vitrite is observed as rare, but broad bands, palmately branching at the ends.

Among the mineral inclusions there is pyrite, which fills cracks in the coal.

VI variety of coal. This variety of coal is petrographically identical with the VI variety of coal of sample No. 1. Just as there, it is macroscopically characterized by a gray color, a dense homogeneous structure, and microscopically consists of the same ingredients. The technical composition of the coal of this variety differs somewhat from that in sample No. 1. Here the ash content and the yield of volatile substances are somewhat reduced (Table 5).

VIII variety of coal. The coal of this variety is petrographically quite identical with the coal of the VIII variety from sample No. 1 and differs only in lower ash content and a smaller yield of volatile substances (Table 5).

Thus, here also, as in sample No. 1, all the varieties of coal are arranged in the same order, that is, from lustrous to dull. But here they all possess a more clearly expressed differentiation of petrographic composition, i.e. in the coal varieties of this sample the banding and streakiness appear more distinctly. In addition, the character of the luster of the lustrous coal here already stands closer to glassy, and it may be called intermediate between glassy and resinous.

The change in the micropetrographic and technical compositions proceeds in the same order as in sample No. 1 (Table 5). But here the percentage content of vitrite increases, while that of ksilovitrite decreases. In addition, in the coal varieties of this sample clarite is not observed at all. The yield of volatile substances is also reduced here.

Sample No. 3. In the composition of this sample of the seam there are six varieties: I, II, III, IV, VI, and VIII, characterized as follows.

I variety of coal. Macroscopically, glassy-lustrous coal of black color, with a banded structure. The fracture is angularly uneven. The streak is black. The cleavage is vertical and is well expressed. Along the cleavage cracks the coal is easily split into even slabs 1.5–2 cm thick. The coal is weak, easily breaking down into small pieces under the slightest mechanical efforts. On the planes of the cracks, very thin films of calcite and pyrite are observed.

Microscopically it consists of durite and vitrite, with an insignificant content of ksilovitrite, ksilite, and fusite (Table 6).

Table 5

Name of coal varieties	Durite	Vitrite	Xylovitrite	Xylite	Fusite	Durite composition: structureless mass	Durite composition: form elements	\(W^a\)	\(A^a\)	\(V^a\)	\(A^c\)	\(V^c\)	\(V^2\)	Character of the coke button
I variety	55	38	3	3	1	89	11	0,85	1,75	22,71	1,76	22,90	23,32	Fused, moderately swollen, steel-gray
II variety	71	6	6	12	4	87	13	0,80	2,41	20,94	2,42	21,10	21,63	Fused, slightly swollen, steel-gray
III variety	63	10	3	17	7	86	14	0,91	2,89	20,37	2,91	20,56	21,17	Fused, low steel-gray
IV variety	64	3	2	14	18	77	23	0,81	7,38	18,98	7,44	19,07	20,67	Fused, low steel-gray
V variety	48	6	2	8	37	84	16	0,75	1,77	17,91	1,78	18,04	18,37	Fused, low, gray in color, with a finely humped structure at the top
VI variety	67	2	2	21	7	65	35	0,90	6,82	16,49	6,88	16,64	17,87	Sintered, black
VIII variety	—	—	—	—	—	—	—	0,58	12,88	22,87	12,95	23,00	26,42	Fused, weakly swollen, steel-gray

Durite in polished sections occurs as broad fields and is characterized by a weak saturation with form elements. Among the form elements here, as in variety I of sample No. 2, there are observed: pale-yellow, low-relief, structureless formations of indeterminate nature; rounded bodies of yellow color, sometimes smooth, sometimes with a noticeable streaky structure. Bodies of round and ellipsoidal form with a spongy-porous structure and a thin peripheral rim are often encountered (Table III, Fig. 1); formations of round form with a coarse-cellular structure are observed more rarely (Table III, Fig. 2).

Vitrite occurs in broad bands with clearly expressed transverse cracking. It is interesting to note that the vitrite bands here do not have clearly expressed boundaries, since almost all of them have gradual transitions on one side into xylite, and on the other—into durite.

The gradual transition from vitrite to xylite proceeds through the following stages. At first, small yellowish-pale spots appear toward one edge of the vitrite band, becoming visible when the microscope tube is moved. Then these spots merge and produce a continuous pale-yellow structureless band, in which separate, very rare dots appear and the intensity of the yellow coloration increases. Finally, this transition ends in typical xylite with a clear dotted structure, pale-yellow coloration, and high relief. The transition from vitrite to durite proceeds in the following way. Toward the edge of the vitrite band opposite to the xylite edge, at first rare inclusions of structural and form elements begin to appear; then they become more and more numerous and, finally, the vitrite band merges with normal durite. This phenomenon of a gradual transition from durite through vitrite to xylite gives, to a certain extent, grounds for assuming that the structureless basic mass of durite is nothing other than plant tissue decomposed to the state of a colloid.

Normal xylite is not observed here, but lens-shaped formations are often encountered, consisting of yellow, tangled-fibrous plant tissue with inclusions of rather large fragments of the same color, but with a distinct cellular structure (Plate III, Fig. 1). Broad, spot-like formations of finely cellular fusite are rarely observed here. Sometimes, on these fusite spots, accumulations of angular, structureless fragments of yellow color are visible (Plate III, Fig. 3).

Among the mineral inclusions there is pyrite, which fills almost all the small cracks present in the coal.

II variety of coal. Macroscopically, it is a semilustrous coal of grayish-black color, of finely striated composition. The fracture is angular-uneven. The streak is black—dry. The jointing is vertical, as in the coal of the I variety, but is less pronounced. There is frequent discontinuous fissuring, running at an angle of \(30^\circ\) to the joint cracks. Its composition, in addition to vitrite needles and the principal semimatte mass, shows very rare fusite lenses \(0.5—1\) mm thick.

Microscopically, it is composed almost exclusively of durite, with a small amount of vitrite and xylite and an extremely small content of xylovitrite and fusite (Table 6).

The main field of the section is usually occupied by durite of the same character as in the coal of the I variety. Scattered among this durite are the finest pointed vitrite lenses, fragments of xylovitrite, xylite, and fusite lenses.

Among the mineral inclusions, as in the coal of the first variety, there is pyrite.

III variety of coal. Macroscopically, it is a semimatte coal of dark-gray color, of finely banded composition. The fracture is coarse, angular-uneven. The streak is black. There are rare vertical, dying-out cracks. Its composition shows frequent inclusions of the finest fusite lenses and thin cords and needles of vitrite.

Microscopically, it is composed predominantly of durite with a subordinate position of vitrite, xylite, and fusite and with an insignificant content of xylovitrite (Table 6).

Durite occurs in the sections as broad fields, either in the form of wedging-out and branching bands, or in the form of broad shapeless spots. It is characterized by a rather strong saturation with various formed structures. Among the latter, fragments of xylite and fusite tissues and rounded bodies of yellow color, with a dash-like and porous-toothed structure, are more often observed.

Vitrite is observed as broad, wedging-out bands. Often these bands, toward the side of wedging-out, break up into the thinnest fibers, which then gradually merge with the main structureless mass of the durite. Here, just as in the coal of the I variety, gradual transitions from vitrite to xylite are observed.

Xylite forms broad, blunt-ending lenses, which at the ends sometimes branch in a paw-like manner into narrower areas. In addition, in some xylite lenses, gradual transitions into finely cellular fusite are observed toward one of their ends.

As in the coal of the III variety of sample No. 2, xylite is observed as accumulations of narrow ribbon-like bands and angular pieces of plant tissue in the main yellow porous-toothed mass. But the areas of such xylite here are deformed into oblique folds (Plate III, Fig. 4).

Fusite is observed in the form of broad, breaking-off bands. It has a clearly expressed finely cellular structure. The cell openings are sometimes round, sometimes flattened.

Of the mineral inclusions, pyrite is observed in the form of very small angular pieces located among the fusite areas and in cracks.

IV variety of coal. Macroscopically, a dull coal of gray color, dense, of finely striated structure. The fracture is rough, angular-uneven. The streak is black. Frequent vertical fissuring is present. Along these cracks the coal readily splits into thin plates 2–3 cm thick. On the planes of the cracks, the thinnest films of pyrite are observed.

Microscopically, it consists mainly of durite with subordinate xylite and fusite and with an insignificant content of vitrite and xylovitrite (Table 6). All these ingredients in the polished sections are arranged in a disorderly manner, giving the coal a spotted, variegated structure. The main field of the polished section is usually composed of durite, in which broad formations of fusite and xylite, with diffuse outlines, are scattered disorderly, as well as rare needles of vitrite and short plates of xylovitrite.

Among the mineral formations, pyrite is observed, filling cracks in the coal.

VI variety of coal. Petrographically this variety is identical to the VI variety of coal of samples No. 1 and No. 2, but chemically it differs by an even greater reduction in volatile substances (Table 6).

VIII variety of coal. Petrographically the coal of this variety is identical to the VIII variety of coal from samples No. 1 and 2. In the content of volatile substances on the combustible mass it almost approaches the coal of the VIII variety of sample No. 1, but at the same time has an incomparably greater ash content (Table 6).

Table 6

Name of coal varieties	Durite	Vitrite	Xylovitrite	Xylite	Fusite	Structureless mass	Formed formations	$W^a$	$A^a$	$V^a$	$A^c$	$V^c$	$V^z$	Character of the coke button
I variety	61	28	4	6	1	89	11	0.78	2.30	16.32	2.31	16.45	16.83	Fused, swollen, steel-gray in color
II ”	81	8	2	8	1	91	9	1.02	2.32	15.12	2.34	15.28	15.64	Fused, moderately swollen, steel-gray in color
III ”	68	10	3	12	7	87	13	0.81	4.20	14.87	4.23	14.99	15.66	Fused, weakly swollen, steel-gray in color
IV ”	67	4	1	16	11	83	17	0.87	6.07	14.75	6.13	14.88	15.85	Sintered, with a fused top, steel-gray in color
VI ”	73	1	2	22	3	65	35	0.70	5.67	12.99	5.70	13.08	13.88	Sintered
VIII ”	—	—	—	—	—	—	—	0.36	32.65	22.47	32.76	22.53	33.54	Fused, moderately swollen, steel-gray in color

And here, just as in the first two samples, all varieties differ macroscopically from one another in luster and structure, and microscopically and chemically in composition (Table 6). But from the coal varieties of the first

of the two samples they differ by an entirely clear macroscopic differentiation of the petrographic composition and by a reduced content of volatile substances. In addition, the lustrous varieties of coal here already acquire a pure glassy luster, whereas in sample No. 1 the lustrous varieties have a resinous luster, and in sample No. 2 an intermediate luster (between glassy and resinous).

Thus, seam VI Internal at the points studied by us consists mainly of six varieties of coal: I, II, III, IV, VI, and VIII. The fifth variety is observed only in sample No. 2, and the seventh only in sample No. 1 and, as we shall see below, in very insignificant quantities.

It is also evident from the description given that the main varieties of coal of seam VI Internal at each studied point differ in their particular petrographic as well as chemical properties. But before proceeding to a comparative analysis of the component parts of the seam by the points studied, we shall first acquaint ourselves with the general structure of the seam at these points and at the same time determine the quantitative content of the coal varieties in each sample separately.

2. Structure and composition of the seam.

Sample No. 1 was taken, as already indicated, in mine No. 7 in the face of the main drift, 157 m south of the northern crosscut. The thickness of the seam at the sampling site is 3 m. The floor of the seam is a dark-gray dense argillite with an uneven conchoidal fracture. It is strongly broken by fissures of various orientation and easily falls apart into irregular pieces with slickensides. Rarely, imprints of plant remains of very poor preservation and inclusions of coaly fibers are observed in it. Directly on the floor of the seam lies an interbed, 0.12 m thick, of strongly crushed coal. This interbed of crushed coal is called by the local workers the “undercutting.” It consists of weakly compacted thin rhomboidal laminae of coal with lustrous surfaces, contaminated by small pieces of coaly argillite which, like the pieces of coal, also have lustrous surfaces. All these data, of course, leave no doubt that the undercutting, with its typical tectoclastic texture, is the result of intense interstratal displacements that occurred, probably, during the period of formation of the principal folds of the district, and was formed at the expense of the marginal parts of the seam, thereby reducing its useful thickness. Above this undercutting begins the useful part of the seam, the petrographic section of which, from bottom to top, is as follows (see also drawing 1 of Table V).

Brief description of the coal	Average thickness of the interbeds in mm
1. Vitrite—lustrous homogeneous black coal. Fracture flat-conchoidal. Separateness parallelepipedal, rarely oval, resembling eyebright. In the right part of the interbed, wedging bands of variety III coal are observed . . . . . . . . . . . . . . . . . . . . . .	30
2. Variety I coal—resin-lustrous black coal, of striated, in places indistinctly thin-banded structure. At the top of the interbed there are bands of vitrite wedging out and branching into thin fibers. In the right part of the interbed there is a wide wedging band of variety III coal. The entire interbed is broken, in places, by thin cracks running at an angle of 45° to the bedding. On the planes of the cracks, small oval white and brownish spots of calcite are observed . . . . . . . . . . . .	72

Brief description of the coal	Average thickness of the bands, in mm
3. Fusite—coal of dark-gray color, fibrous texture, with a weak silky luster, hard, weakly soiling	3
4. The same as No. 2. At the top of the band, on the right side, a small lens of hard fusite is observed	42
5. Vitrinite. On the left side the band branches strongly into thin strips, which penetrate into coal of variety III. The vitrinite is strongly broken by thin parallel cracks running perpendicular to the bedding. The planes of the cracks are coated with films of light-brown calcite	17
6. Variety III coal—dull coal of dark-gray color, weakly banded, dense texture. Throughout the band are scattered the thinnest strips of vitrinite and the smallest lenses of fusite	8
7. Variety VI coal—dull coal of gray color, dense, almost homogeneous texture	80
8. Dark gray, in places with brownish mottling, sandy-coaly argillite. The band is broken by horizontal cracks with slickensides	34
9. The same as No. 7	8
10. Variety I coal	9
11. Variety VI coal. At the top the band is bounded by a tectonic crack running parallel to the bedding. The surfaces of the crack are glossy, rubbed	70
12. Variety I coal	49
13. Vitrinite	6
14. Variety I coal	19
15. Vitrinite	5
16. Variety I coal	102
17. Variety VI coal	26
18. Variety III coal. At the bottom of the band there pass frequent thin strips of vitrinite. A thin, dying-out fissuring is indicated, running perpendicular to the bedding	45
19. Variety I coal	7
20. Hard fusite. Occurs in the form of a lens 150 mm long	10
21. Vitrinite. The band is strongly destroyed into small pieces cemented by brown matter. To the right the band gradually wedges out, and to the left it passes into strongly disintegrated vitrinite, bordered above and below by a fusite fringe	12
22. Hard fusite. Occurs as small thin lenses. The length of the lenses reaches 50 mm, and the width up to 4 mm	3
23. Variety I coal; from the fusite it is bounded by a thin strip of vitrinite, 2 mm thick	14
24. Variety II coal. Semi-bright dense coal of dark-gray color, with inclusion of the thinnest needles of vitrinite. In the center of the band vitrinite is observed in the form of a large lens 3 mm thick. This vitrinite lens wedges out toward the right end, and toward the left it branches	12
25. Variety I coal. The band is broken by frequent vertical cracks. The planes of the cracks are coated with films of calcite	32
26. Variety III coal	26
27. Variety I coal. The band is broken by frequent vertical cracks	42
28. Variety III coal. At the bottom of the band there passes a strip of strongly broken vitrinite; to the right this strip of vitrinite branches into thin fibers	33
29. Variety I coal. The right half of the band is strongly broken and mineralized by brown calcareous-clayey matter	17
30. Variety III coal	50
31. Vitrinite. At the top the band is strongly destroyed into small pieces, which are cemented by brown matter	15
32. Variety I coal	25
33. Variety III coal. The band is cut by a tectonic crack running at an angle of 70° to the bedding	124
Strongly crushed part of the seam	330
34. Variety III coal. Rare scattered strips of vitrinite 3–4 mm thick and small lenses of fusite are observed. The latter are grouped in the upper part of the band	386

Brief description of the coal	Average thickness of interbeds, in mm
35. Vitrinite. In the middle part the interbed is strongly crushed into small pieces, cemented by a brownish clayey substance	23
36. VIII variety of coal. Dull granular coal, strongly mineralized. The finest inclusions of pyrite and concretions of calcite are observed. The interbed is broken by vertical cracks, on the planes of which iridescent films of marcasite of yellowish-green color are observed	135
37. III variety of coal. At the bottom of the interbed frequent vitrinite bands 1–2 mm thick are observed. Fusite is rarely encountered in the form of the thinnest lenses	123
38. Vitrinite. To the right the interbed branches into thin fibers that penetrate into coal of the II variety	10
39. II variety of coal. The interbed is broken by frequent thin vertical cracks	20
40. III variety of coal	99
41. II variety of coal	30
42. Black carbonaceous argillite. The interbed wedges out to the left	5
43. II variety of coal	17
44. Alternation of thin wedging bands of carbonaceous argillite and vitrinite	17
45. Strongly mineralized dense coal. Toward the right side of the interbed the mineralization weakens, and the thinnest vitrinite bands appear	12
46. II variety of coal. The interbed branches to the right into small bands that penetrate into the carbonaceous argillite	7
47. Black carbonaceous argillite	10
48. II variety of coal	61
59. Vitrinite	5
50. IV variety of coal. Dull, slightly glossy coal of gray color, dense, of almost homogeneous composition. Very rare finest needles of black fusite are observed	97
51. III variety of coal	210
52. VI variety of coal	46
53. III variety of coal	47
54. VII variety of coal. Dull homogeneous coal of gray color, with a conchoidal fracture. Coal of this variety is close to carbonaceous argillite	31
Useful thickness of the seam is equal to	2.78 m

Above the coal of the VII variety lies an interbed of soft coal of the same character as the “podkalochnik.” The thickness of this interbed is 0.10 m. The roof of the seam is composed of dark-gray dense argillite, broken by frequent, variously oriented cracks with slickensides.

From the section presented it is evident that the seam, by an interbed of carbonaceous argillite (interbed No. 8), is divided into two benches unequal in thickness; moreover, the second bench, on the basis of its different petrographic composition, may be divided into two parts or into two independent benches, taking as the boundary between them the interbed of coal of the VIII variety (interbed No. 36), which stands out very distinctly in the structure of the seam by its habit sharply different from all other coal interbeds and, in addition, has excellent persistence in all the samples studied.

Thus, on the basis of stratigraphic features and on the basis of petrographic composition, three benches are distinguished in the structure of the seam (drawing 1 of Table V). The first bench, as is evident from the section, has an insignificant thickness—0.253 m. It is composed chiefly of the first and sixth varieties of coal, with a subordinate occurrence of vitrinite and the III variet-

of the coal and a very low content of fusite (Table 7), the latter ingredients occurring as scattered bands (vitrain), small lenses (fusite), and wedging-out interlayers (III coal variety) among a broad interlayer of the first coal variety, which occupies the entire lower half of the bench. The upper half of the bench is composed of a homogeneous interlayer of the sixth coal variety, which in the upper horizons is gradually enriched with mineral admixtures and passes into a coaly argillite that completes the structure of the bench (drawing 1 of Table V).

The second bench of the seam has a thickness equal to 1.5 m. It is composed mainly of the third and first coal varieties, with subordinate occurrence of vitrain and the sixth coal variety (Table 7). The sequence of occurrence of the petrographic composition here is in general the same as in the first bench. Here, as there, bright coal (the first variety and vitrain) occurs in the lower half of the bench, the first variety occurring in more or less broad interlayers alternating with similar interlayers of the third coal variety, thin bands of vitrain, and very rare lens-shaped formations of fusite. The upper part of the bench, from the beginning of interlayer No. 33 to the end of the bench, is composed exclusively of the third coal variety with very rare bands of vitrain. The petrographic composition of the destroyed part of the bench, shown in the drawing by a break in the column, remains unclear (drawing 1 of Table V). The bench ends with a rather broad band of vitrain, which in its upper part acquires a granular structure and gradually passes into a broad interlayer of the eighth coal variety.

With an interlayer of the eighth coal variety begins the third bench of the seam, with a thickness of 0.983 m. In petrographic composition this bench of the seam is distinguished by an exceptionally low content of bright ingredients. The first coal variety is not observed here at all, while vitrain occurs in the form of very rare and thin wedging-out bands. Its principal constituent part is the third coal variety, which occurs in broad interlayers alternating with very rare interlayers of the second coal variety and single interlayers of the fourth and sixth coal varieties (drawing 1 of Table V). In the composition of the interlayer of the second coal variety (interlayers 41—48), frequent wedging-out interlayers of black coaly argillite are observed. The end of the formation of the bench is completed by the sixth coal variety, which, becoming enriched with mineral admixtures, gradually passes into the seventh coal variety.

The quantitative petrographic composition of this bench is given in Table 7.

Table 7

Macropetrographic composition of seam VI Internal at point No. 1
(mine No. 7).

Nos. of benches	Vitrain	I variety	II variety	III variety	IV variety	VI variety	VII variety	VIII variety	Fusite	Coaly argillite
I bench . . . . . . .	21	34	—	13	—	30	—	—	2	—
II bench . . . . . . .	8	26	1	53	—	9	—	1	1	—
III bench . . . . . . .	4	—	13	45	10	7	4	14	traces	2
For the seam as a whole .	8	16	6	46	4	10	1	6	traces	2

Thus, from Table 7 it is evident that the lower part of the seam (the first bench) contains the greatest amount of bright coal, vitrite, and the first variety; in the middle part of the seam (the second bench) the content of vitrite and of the first variety becomes smaller, and in the upper part of the seam (the third bench) the first variety is not observed at all, while the content of vitrite decreases sharply. In general, at this point the seam is composed of the third variety of coal, with subordinate occurrences of the first and sixth varieties, a small content of vitrite, the second and fourth varieties of coal, and a very small content of the seventh variety of coal, fusite, and pure mineral impurities.

Sample No. 2 was taken in mine No. 5, in the face of the first parallel crosscut, 70 m south of survey point No. 2364. The thickness of the seam at the sampling site is 3.15 m. The floor of the seam here, as in mine No. 7, is a dark-gray dense argillite with a splintery-conchoidal fracture, which, as there, is strongly crushed and easily breaks into small shell-like pieces with slickensides. Directly on the floor lies a layer of “under-clay” of the same character as in mine No. 7, but of somewhat greater thickness—0.20 m. The section of the useful part of the seam here is as follows, from bottom to top (drawing 2 of Table V).

No.	Brief description of the coal	Average thickness of the layer, in mm
1.	IV variety of coal. Dull coal of gray color, dense, of indistinctly streaky composition. The fracture is angular-uneven. In its composition, besides the principal dense gray mass, there are rarely scattered very small lenses of fusite and needles of vitrite. There is weak, fading fissuring, running perpendicular to the bedding.	32
2.	I variety of coal. Bright coal of black color, thinly banded, in places of streaky composition. The fracture is flat, with barely noticeable hummockiness. Vertical separateness is clearly expressed. Along cracks of separateness the coal readily splits into thin plates 1–1.5 cm thick.	49
3.	III variety of coal. Semidull coal of grayish-black color, distinctly banded composition. The banding is caused by the frequent alternation of thin (from 0.5 to 1.5 mm) bands of vitrite with more or less broad (5–6 mm) bands of dull coal. In addition to vitrite, very small scattered lenses of fusite are also rarely observed here. There is rare, weakly expressed vertical fissuring.	45
4.	V variety of coal. Dull coal of black color, of very fine banded composition, caused by a very close alternation of threadlike cords and lenses of fusite with similar cords of dull and bright coal.	50
5.	IV variety of coal.	13
6.	V variety of coal. In some parts of this layer fusite forms accumulations in the form of long lenses 100 mm long and 5 mm wide.	15
7.	IV variety of coal.	25
8.	V variety of coal.	4
9.	VI variety of coal. Dull coal of gray color, dense, of homogeneous composition. The fracture is coarse, angular-uneven.	30
10.	I variety of coal. The layer is strongly crushed by thin vertical cracks.	20
11.	V variety of coal. The layer contains frequent, wedging-out bands of vitrite.	6
12.	Vitrite.	7
13.	III variety of coal. In the layer there are observed, in large quantity, bands of vitrite 2–3 mm thick and lenses of coal of the fifth variety. There is frequent vertical fissuring, which, however, does not affect the lenses of coal of the fifth variety.	42
14.	Alternation of bands of coal of the fifth variety with wedging-out bands of coal of the third variety.	32

Brief description of the coal	Average thickness of the interbed in mm
15. III variety of coal	6
16. V variety of coal	12
17. III variety of coal with sparsely scattered small lenses of fusite and rare lenses of coal of the fifth variety	25
18. V variety of coal	10
19. VI variety of coal	15
20. Dark gray, with a brownish tint, carbonaceous argillite with inclusions of rare vitrite fibers	38
21. VI variety of coal	87
22. I variety of coal with clearly expressed vertical cleavage. On the cleavage planes thin rounded films of pyrite are observed	28
23. III variety of coal	17
24. Vitrite with excellently expressed conchoidal cleavage. The interbed is strongly broken by thin, frequent vertical cracks. On the crack planes there are oval films of calcite and pyrite	97
25. I variety of coal. The interbed is strongly fractured. There are large cracks with slickensided planes. These cracks run at an angle of 40–45° to the bedding. In addition, small cracks are strongly developed here, running in two directions. Some are parallel to the large cracks, others perpendicular to the bedding. In the cracks small films of pyrite and calcite are observed. At the very top of the interbed, on the left, a band of strongly mineralized coal wedges in	320
26. Vitrite, strongly contaminated with calcite and clay	20
27. IV variety of coal	70
28. III variety of coal. The interbed is strongly broken by vertical cracks	80
29. I variety of coal. The interbed is strongly broken by cracks. Frequent, very fine inclusions of pyrite are observed	223
30. II variety of coal. Semi-lustrous coal of gray-black color, dense, of weakly striated structure. The fracture is uneven, finely hummocky. The interbed is broken by frequent vertical fracturing	34
31. I variety of coal	17
32. II variety of coal	23
33. I variety of coal	19
34. II variety of coal. At the top of the interbed frequent vitrite bands 3–4 mm thick are observed	94
35. VIII variety of coal. Dull, granular, strongly mineralized coal. The interbed is broken by rare vertical cracks. The crack planes are almost entirely covered with small film-like formations of pyrite	124
36. II variety of coal	92
37. Vitrite	9
38. I variety of coal	16
39. IV variety of coal	158
40. I variety of coal	21
41. II variety of coal. On fractures, fine pyritization is observed	210
42. Dark gray fusite-bearing interbed, very friable	8
43. IV variety of coal	16
44. Same as No. 42	11
45. IV variety of coal. On the left, in the upper part of the interbed, a wedging-out band of the same formation as in interbeds No. 42 and No. 44 is observed	18
46. II variety of coal	35
47. IV variety of coal with scattered small lenses of fusite and rare bands of vitrite	215
48. I variety of coal	13
49. VIII variety of coal	14
50. II variety of coal	42
51. VI variety of coal. The interbed is strongly broken by vertical cracks. The crack planes are covered with a continuous film of pyrite. Fine pyritization, moreover, is also observed on fractures	165
52. II variety of coal	26
53. VI variety of coal	52
Useful thickness of the seam is equal to	2.85 m

Above the bed of the sixth variety of coal, as in the first case, lies a bed of dull coal with a thickness of 0.10 m. The roof of the seam is the same dark-gray argillite as in sample No. 1.

The structure of the useful part of the seam, as may be seen from the section given (Fig. 2 of Table V), here remains the same as at point No. 1. Here, just as there, the seam is divided by the same interbed of carbonaceous argillite (interbed 20) into two packs correspondingly unequal in thickness, and the second pack, in turn, on the basis of different petrographic composition, is divided by an interbed of the eighth variety of coal (interbed No. 35) into two parts or independent packs. However, in petrographic composition the given seam sample differs considerably from sample No. 1.

The first pack of the seam here has a more complex petrographic composition than in sample No. 1, and a greater thickness—0.44 m. It consists mainly of a more or less close alternation of interbeds of the fifth and fourth varieties of coal, with a subordinate position of the third and first varieties of coal and a comparatively small content of vitrite and of the sixth variety of coal (Table 8). At the same time the sequence of occurrence of the ingredients also changes. Thus, the first variety and vitrite are observed here both in the lower half of the pack and in its upper half (Fig. 2 of Table V), although the structure of the pack ends, as in the first case, with the sixth variety of coal, which, gradually becoming enriched in mineral impurities, passes into carbonaceous argillite. The carbonaceous argillite, in turn, is gradually replaced by coal of the sixth variety, with which the structure of the second pack begins.

The second pack of the seam at this point is characterized by a high content of lustrous coal of the first variety and vitrite and by a low content of dull ingredients (Table 8).

The first variety of coal here occurs mainly in two broad interbeds, separated by coal of the fourth and third varieties (interbed No. 27 and interbed No. 28). Bands of vitrite, reaching a thickness of 97 mm (interbed No. 24), are associated with the lower interbed of the first variety of coal. The upper interbed of the first variety is overlain by semilustrous coal of the second variety, in the composition of which rare bands of the first variety of coal and vitrite are observed. The second pack of the seam ends with coal of the second variety (Fig. 2 of Table V). The thickness of the second pack here is 1.13 m.

Table 8

Macropetrographic composition of seam VI Internal at point No. 2
(mine No. 5).

Nos. of packs	Vitrite	I variety	II variety	III variety	IV variety	V variety	VI variety	VII variety	Fusite	Carbonaceous argillite
1 pack	8	15	—	15	21	32	10	—	—	—
2 pack	16	49	13	7	6	—	8	fractions	fractions	—
3 pack	3	4	32	—	30	—	17	11	2	—
By seam	9	21	20	5	20	5	12	5	1	1

The third pack of the seam here, as at point No. 1, begins with an interbed of the eighth variety of coal. Its composition includes, in almost equal amounts, the second and fourth varieties of coal, with a subordinate posi-

…of the sixth variety and a very small amount of the first variety of coal and vitrain (Table 8). All the main ingredients of the seam occur as broad interlayers, standing out more or less clearly. The formation of the seam ends with the sixth variety of coal. The thickness of the seam is 1.25 m.

Thus, the seam in mine No. 7 and mine No. 5 has, in general, the same structure, but a more or less different petrographic composition (Table 8). If in mine No. 7 the third variety of coal strongly predominates in the composition of the seam, then in mine No. 5 the third variety of coal is observed in insignificant quantities; instead, the content of the second and fourth varieties of coal greatly increases, and the content of the first variety of coal and vitrain also increases.

Sample No. 3 was taken in adit No. 11, at the face of the main crosscut, at a distance of 12.3 m from furnace No. 24. The thickness of the seam at the place where the sample was taken is 3.30 m. The floor of the seam, as at the first two points, is a dark-gray dense argillite, broken by frequent cracks with slickensides. On the floor of the seam lies an interlayer of seat earth 0.12 m thick, above which begins the useful part of the seam, whose section from bottom to top is as follows (drawing 3 of Table V).

Brief description of the coal	Thickness of interlayer in mm
1. VI variety of coal; dull coal of gray color, of dense homogeneous composition	99
2. III variety of coal. Semi-dull coal of dark-gray color, thin-banded structure. The fracture is rough, uneven. In the composition of the interlayer, in addition to the main dull part, the thinnest strips of vitrain and rare small lenses of fusain are distinguished. The interlayer is broken by frequent vertical cracks	25
3. Vitrain	20
4. I variety of coal. Bright coal of black color, thin-banded structure. The fracture is uneven. Frequent vertical fissuring is present. On the planes of the cracks, rounded films of pyrite are observed	47
5. IV variety of coal. Dull coal of dark-gray color, with a fine-streaked structure caused by the inclusion of the finest needles of vitrain and fusain. Fissuring is weakly manifested	20
6. Vitrain	11
7. Dark-gray, almost black carbonaceous argillite. Below, it is separated from the vitrain by a tectonic crack with a distinct slickenside. Cracks with slickensides are also observed within the interlayer	192
8. I variety of coal. The interlayer is strongly broken by vertical cracks	9
9. Vitrain	10
10. I variety of coal	15
11. Vitrain	61
12. VI variety of coal. The interlayer is cut by a tectonic crack running at an angle of 15° to the bedding. The surfaces of the crack are striated	26
13. IV variety of coal. Throughout the interlayer, rare inclusions of thin strips of vitrain and small lenses of fusain are observed	89
14. I variety of coal. Coal with a well-pronounced fine banded structure, caused by frequent alternation of vitrain bands 2–3 mm thick with bands of bright, fine-streaked coal. Vertical jointing is well expressed. Along the joint cracks the coal readily breaks up into slabs 1.5 cm thick	13
15. Vitrain. The interlayer wedges out on the right side of the hand specimen. At its upper boundary there is a fusain lens 35 mm long and 5 mm wide	24
16. I variety of coal	8
17. Vitrain	51
18. III variety of coal. In the middle of the interlayer a strip of vitrain is observed. There are lenses of fusain, grouped in the upper part of the interlayer	18
19. Vitrain	18

Brief description of the coal	Bed thickness in mm
20. I variety of coal. At the bottom of the bed there are fusite lenses 50–40 mm long and 2–3 mm thick	17
21. Vitrite. Toward the right side of the adit face it branches into thin cords	9
22. III variety of coal. In the lower part of the bed, immediately above the vitrite, fusite lenses are observed	23
23. Vitrite	22
24. III variety of coal	4
25. I variety of coal. In the middle of the bed two vitrite bands, 4 and 8 mm thick, stand out clearly	128
26. IV variety of coal, with inclusions of the smallest fusite lenses	5
27. I variety of coal	13
28. III variety of coal	39
29. Vitrite. The band is strongly destroyed and pyritized	36
30. I variety of coal	35
31. II variety of coal. Semilustrous coal of grayish-black color. The fracture is uneven. Vertical cleavage is well expressed. In its composition, besides the semilustrous principal mass, frequent vitrite needles and rare very small fusite lenses are observed	27
32. I variety of coal	13
33. IV variety of coal	75
34. Vitrite	7
35. IV variety of coal	14
36. Vitrite	6
37. II variety of coal	67
38. IV variety of coal	56
39. Vitrite; toward the right side of the adit face the band divides in two. In the middle of the fork lies coal of the first variety of coal	13
40. I variety of coal	39
41. Vitrite	9
42. VIII variety of coal. Dull, strongly mineralized coal of granular structure. Inclusions of strongly destroyed vitrite bands are observed. The bed is cut by rare vertical cracks. The cracks are filled with sparkling films of marcasite	104
43. I variety of coal. Downward, the bed gradually acquires a granular structure and then merges with coal of the VIII variety. The upper part of the bed is cut by frequent vertical cracks	83
44. III variety of coal, cut by vertical cracks. In the lower part of the bed inclusions of vitrite bands are observed	68
45. I variety of coal with inclusions of vitrite bands reaching 10 mm in thickness	46
46. III variety of coal. At the top of the bed there passes a horizontal tectonic crack with slickensides	126
47. Hard mineralized fusite with thin irregular vitrite cords	16
48. VI variety of coal with inclusions of thin fusite lenses and vitrite bands 3–4 mm thick	128
49. I variety of coal	41
50. VI variety of coal. In the lower half of the bed there passes a horizontal tectonic crack with slickensides	89
51. III variety of coal. The bed is bounded above and below by vitrite bands 4–6 mm thick	14
52. IV variety of coal	87
53. III variety of coal	60
54. VI variety of coal	227
55. III variety of coal. Rare vertical fracturing is observed. The cracks are filled with pyrite	66
56. VI variety of coal	60
57. III variety of coal. Along the middle of the bed there passes a vitrite band 13 mm thick	31
58. I variety of coal with prominent vitrite bands, from 2 to 13 mm thick	43
59. III variety of coal. In the upper half of the bed there are inclusions of fusite lenses 25–30 mm long and 3–4 mm thick	115

Brief description of the coal	Thickness of the interlayer in mm
60. VI variety of coal with inclusions of small fusite lenses. The interlayer is strongly broken by vertical cracks	47
61. III variety of coal	44
62. Quartzose coal-bearing sand	5
63. Vitrite	7
64. III variety of coal	113
65. VI variety of coal	76
66. III variety of coal. In the upper half of the interlayer an accumulation of fusite lenses is observed	89
67. VI variety of coal	10
Useful thickness of the seam	3.18 m

The interlayer of dull coal—the “seat rock”—in the roof of this seam section is absent, and the roof of the seam begins with a thin interlayer, 0.20–0.25 m thick, of grayish-black carbonaceous argillite, with a mass of carbonized plant remains and, rarely, impressions; both, however, are very poorly preserved. Above this interlayer of carbonaceous argillite lies gray argillite, identical with the roof of the seam in the first two packs.

The structure of the seam here is, in general, the same as at the first two points. Here, just as there, the seam is divided into two packs, of which the upper one, on the basis of its different petrographic composition, is divided into two independent parts, or packs. The boundaries between the packs are the same formations: that is, the boundary between the first two packs is a thin interlayer of carbonaceous argillite, and the boundary between the last two packs is an interlayer of the eighth variety of coal (drawing 3 of Table V). However, the petrographic composition both of the seam as a whole and of the corresponding packs of this section differs more or less from its petrographic composition at the first two points.

The first pack of this section is composed predominantly of the sixth variety of coal, with subordinate occurrence of the first and third varieties of coal and a comparatively small content of vitrite (Table 9). The sequence of occurrence of the component parts here presents the opposite picture from that in the corresponding pack of the first two sections. Thus, the sixth variety of coal here occurs as a broad homogeneous interlayer directly on the seat rock, while the first variety of coal and vitrite are situated higher up; moreover, the structure of the pack here ends with vitrite, upon which carbonaceous argillite lies, separated from it by a tectonic fracture with slickensides. The thickness of the pack is 0.22 m.

The beginning of the second pack here also differs from the beginning of the second pack at point No. 1 and point No. 2. If there the second pack began with the sixth variety of coal, with a gradual transition from carbonaceous argillite, then here, on the contrary, directly upon the carbonaceous argillite lies a broad interlayer of the first variety of coal, and above it already lies the sixth variety of coal. Above the interlayer of the sixth variety of coal the structure of the second pack more or less becomes aligned with its structure at the first two points. In petrographic composition, here too, as at point No. 2, it is distinguished by a high content of lustrous coal of the first variety and vitrite, and by the subordinate position of the dull varieties of coal (Table 9). The thickness of the pack is 1.18 m.

The third bench of the seam is composed, as in the first two points, almost exclusively of dull varieties of coal. The content of the first variety and of vitrite is insignificant (Table 9), but higher than in samples No. 2 and No. 1. In this sample, in this section, the bench is distinguished by its great thickness, which is equal to 1.80 m, whereas at point No. 1 its thickness is 0.98 m, and at point No. 2—1.25 m. This is apparently explained by the fact that in the given section, at the roof of the seam, the “podkalochnik” is absent, at the expense of which the thickness of the third bench is increased.

Thus, the structure of the seam is maintained in this section as well, although its petrographic composition changes. Here the content of vitrite and of the first variety increases still more than in sample No. 2.

A characteristic feature of this section is the absence of the podkalochnik directly beneath the roof and the increase, at its expense, of the workable thickness of the seam.

Table 9

Macropetrographic composition of seam VI Internal at point No. 3
(adit No. 11).

Nos. of benches	Vitrite	I variety	II variety	III variety	IV variety	VI variety	VII variety	Fusite	Carbonaceous argillite
1st bench	17	21	—	11	7	45	—	—	—
2nd bench	17	44	7	11	14	6	—	1	—
3rd bench	5	11	—	38	6	23	6	1	—
In the seam	10	24	3	26	14	18	3	1	1

IV. On the variability of the coal in the strike direction and on the factors that caused this variability.

Comparing now the data obtained in the study of individual seam column samples, we are convinced that the floor and roof of the seam everywhere consist of dense dark-gray argillite, broken by small cracks of various orientation. Along these cracks it readily breaks down into small irregular pieces with slickensided surfaces.

The workable part of the seam is separated from the floor and the roof by an interbed of strongly crushed coal, contaminated with carbonaceous argillite. This interbed is called by the local workers the “podkalochnik.”

The “podkalochnik” consists of weakly compressed thin platy-rhomboidal pieces of coal with mirror-polished surfaces, mixed with similar pieces of carbonaceous argillite. This indicates that the “podkalochnik” was formed as a result of tectonic bedding-plane displacements, through destruction and mutual abrasion of the layers along which these displacements took place.

The thickness of the “podkalochnik” in the floor of the seam shows insignificant fluctuations. In mine No. 7 (sample No. 1) and adit No. 11 (sample No. 3) its thickness is 0.12 m, while in mine No. 5 (sample No. 2) it is 0.20 m. In the roof of the seam, however, the “podkalochnik” is observed only in mine No. 7 and in mine No. 5; in adit No. 11 it is absent. Its thickness here, both in mine No. 7 and in mine No. 5, is 0.10 m.

The absence of the “podkalochnik” in the roof of the seam in adit No. 11 is evidently explained by the fact that the hanging wing of the seam here either did not at all experience

by the action of interbed displacements, or was affected by them in a very weak form. As a result, the thickness of the useful part of the seam in adit No. 11 increases. In mine No. 7 the useful part of the seam ends with coal intercalation No. 54, composed of the sixth variety of coal, passing upward into the seventh variety of coal. In mine No. 5 the useful part of the seam likewise ends with the sixth variety of coal (intercalation No. 53). Both intercalation No. 54 of sample No. 1 and intercalation No. 53 of sample No. 2 are parallelized with intercalation No. 56 of sample No. 3, composed, as in the first two samples, of the sixth variety of coal. However, above intercalation No. 56 in adit No. 11, instead of the “undercut,” there continues an undisturbed part of the seam with a thickness of 0.60 m. In addition, in adit No. 11, in the roof of the seam, directly upon the coal, there lies an intercalation of carbonaceous argillite 0.20 m thick, which in mine No. 7 and mine No. 5, likewise as part of the useful thickness of the seam, was destroyed by interbed displacements; this evidently accounts for the contamination of the “undercut” with pieces of carbonaceous argillite.

In the coal mass of the useful part of the seam, macroscopically, besides vitrite and fusite, eight varieties of coal are distinguished; they differ from one another in luster, composition, petrographic composition, and technical properties. These varieties, with increasing numbers, are arranged in order of decreasing luster and increasing homogeneity of composition; petrographically, in them there is observed a successive decrease in the lustrous components of the coal and an increase in the dull ones, and chemically—a decrease in the yield of volatile matter and an increase in ash content.

Such a successive change in the petrographic constituent parts of the seam is maintained fairly well from the first to the seventh coal variety. The eighth coal variety stands out sharply from this sequential series in that it has a granular texture, caused by small grains of vitrite scattered in a dull, strongly mineralized, calcite- and marcasite-cemented groundmass. In addition, this coal variety is distinguished also by its technical composition. In it an increased yield of volatile matter is observed, which, to some extent, may be the result of partial decomposition of calcite and marcasite (Tables 4, 5, 6).

It must be assumed that this sharp distinctness in the composition of the seam of the eighth coal variety is explained by the fact that, as follows from its petrographic habitus, it formed as a result of intraseam displacements at the expense of the destruction of lustrous coal. The remaining varieties, however, preserved their primary nature.

The eighth variety of coal occurs as a more or less broad intercalation, persistent at all points of occurrence of the seam (drawing 1 of Table V, intercalation No. 36; drawing 2, intercalation No. 35; drawing 3, intercalation No. 42). The thickness of this intercalation is on average 0.12 m; its greatest thickness is in mine No. 7, where it is 0.13 m, and its smallest—in adit No. 11, where it is 0.10 m. It occurs in the middle part of the seam, dividing it into two benches: in mine No. 7 at a distance of 1.87 m from the floor, in mine No. 5—1.77 m, and in adit No. 11—1.28 m.

In addition, at all points of occurrence of the seam an intercalation of carbonaceous argillite is distinguished (drawing 1 of Table V, intercalation No. 8; drawing 2, intercalation No. 20; drawing 3, intercalation No. 7). The thickness of this intercalation is on average 0.04 m. It occurs in the lower part of the seam: in mine No. 7 at a distance of 0.37 m from the floor, in mine No. 5—0.64 m, and in adit No. 11—0.34 m.

By the intercalation of the eighth coal variety and the intercalation of carbonaceous argillite, the seam at all investigated points is divided into three benches. These benches differ from one another in petrographic composition and in thickness, but at the same time the petrographic composition and thickness of correspondingly named benches are more or less similar in the different samples of the seam (Table 10, from bottom to top).

It is evident from the table that the first (lower) bench of the seam everywhere has an insignificant thickness. Its useful thickness in mine No. 7 and in adit No. 11 is respectively 0.25 and 0.22 m, while in mine No. 5 it reaches 0.44 m.

The petrographic composition of the first bench varies greatly at different points. Thus, in mine No. 7 (sample No. 1) lustrous coal predominates in its composition (the first variety and vitrite). In mine No. 5 (sample No. 2) it consists essentially of dull coal and, chiefly, of the fifth variety, rich in fusite, which is absent both in sample No. 1 and in sample No. 2. In adit No. 11 (sample No. 3) the first bench consists essentially of the high-ash sixth variety of coal, but here the content of lustrous coal (the first variety and vitrite) becomes greater than in sample No. 2 (Table 10).

Table 10.

Name of benches	Sample No.	Vitrite	I variety coal	II variety coal	III variety coal	IV variety coal	V variety coal	VI variety coal	VII variety coal	VIII variety coal	Fusite	Barren rock	Vitrite + I variety	II + III + IV + V variety coal	Useful thickness, m
Bench I	1	21	34	—	13	—	—	30	—	—	2	—	55	13	0.25
Bench I	2	8	15	—	13	21	32	10	—	—	—	—	23	66	0.44
Bench I	3	17	21	—	11	7	—	45	—	—	—	—	38	18	0.22
Bench II	1	8	26	1	53	—	—	9	—	1	1	—	34	54	1.50
Bench II	2	16	49	13	7	6	—	8	—	parts	parts	—	65	26	1.13
Bench II	3	17	44	7	11	14	—	6	—	—	1	—	61	32	1.18
Bench III	1	4	—	13	45	10	—	7	4	14	parts	2	4	68	0.98
Bench III	2	3	4	32	—	30	—	17	—	11	2	—	7	62	1.25
Bench III	3	5	11	—	38	16	—	23	—	6	1	—	16	54	1.80
For the seam	1	8	16	6	46	4	—	10	1	6	parts	2	24	56	2.78
For the seam	2	9	21	20	5	20	5	12	—	5	1	1	30	50	2.85
For the seam	3	10	24	3	26	14	—	18	—	3	1	1	34	43	3.18

The order of occurrence of the lustrous and dull varieties of coal here also changes greatly. In mine No. 7 a successive replacement of lustrous varieties of coal by dull ones is observed. Here, directly upon the “underclay,” lies a band of vitrite, above which comes lustrous coal of the first variety. The first variety of coal is replaced by a thin band of the third variety, which is overlain by a broad interbed of the sixth variety. The latter gradually passes into the carbonaceous argillite that covers the bench.

In mine No. 5 this order is disturbed. Here there is a close interstratification of dull varieties of coal with the fourth and fifth, rare bands of the first variety and vitrite. The bench ends here, as in mine No. 7, with the sixth variety of coal, gradually passing into carbonaceous argillite, which completes the structure of the bench.

In adit No. 11 the order of occurrence of the dull and lustrous varieties of coal becomes the reverse as compared with mine No. 7. Here, directly upon the “underclay,” lies the sixth variety of coal, which occupies the entire lower half of the bench. The sixth variety is overlain by a small band of the third variety, which is replaced by lustrous coal. The carbonaceous argillite covering the bench here lies directly—

directly on the vitrite, separated from it by a tectonic surface with slickensides.

The second bench of the seam is characterized by great thickness. In mine No. 7 its thickness is 1.5 m, in mine No. 5—1.13 m, and in adit No. 11—1.18 m (Table 10).

In petrographic composition this bench is distinguished in the seam by a high content of bright coal (the first variety and vitrite) and a low content of pure dull varieties of coal. Especially much bright coal is observed in its composition in sample No. 2 and in sample No. 3. Here the first variety of coal, together with vitrite, makes up the greater half of the bench (Table 10). In sample No. 1, however, the first variety together with vitrite constitutes only 34%, while the greater half of the bench (53%) is composed of semi-dull coal of the third variety (Table 10).

This bench differs from the first bench also in that everywhere it has a broadly banded structure; moreover, the broad bands of the first variety of coal stand out most distinctly in it, and in their main mass they are confined to the lower half of the bench. In the upper half of the bench, bands of bright coal are observed less often, and they become less thick than below. The upper half of the bench is identical only in the last two samples, while in sample No. 1 it is composed entirely, with the exception of an indistinct destroyed part, of the third variety of coal.

The third bench, like the second, is characterized by great thickness. In mine No. 7 the thickness of its useful part is 0.98 m, in mine No. 5—1.25 m, and in adit No. 11—1.80 m (Table 10).

In its petrographic composition, dull coal predominates throughout. The first variety of coal and vitrite occur very rarely in its composition, and in sample No. 1 the first variety of coal is not observed at all.

The quantitative ratio of the varieties of the same name here, as in the first two benches, differs in the different samples. Thus, in sample No. 1 it is composed of the third variety of coal, with subordinate occurrences of the second, fourth, and eighth varieties. Little coal of the sixth variety is observed; there is also very little coal of the seventh variety, which is absent both in sample No. 2 and in sample No. 3 (Table 10). Let us also note that within this bench, in its middle part, thin wedging-out interbeds of dense carbonaceous argillite are observed (drawing 1 of Table V, interbeds 42, 44, 47).

In sample No. 2 the third variety of coal is completely absent from the composition of the third bench. But here the content of semi-bright coal of the second variety and dull coal of the fourth variety increases greatly, and the first variety of coal also appears, though in an amount of only 4% (Table 10). Here, as in sample No. 1, in the middle part of the bench there are wedging-out bands of barren rock, but not carbonaceous argillite; rather, they are a loose fusite-sandy rock (drawing 2 of Table V, interbeds 42, 44).

In sample No. 3 the predominant position in the composition of the bench is again occupied by the third variety of coal, but at the same time the content of the first variety of coal and vitrite is greater here than in sample No. 2 (Table 10). At the same horizon as in sample No. 2, a thin interbed is present here, composed of loose fusite-sandy rock (drawing 3 of Table V, interbed 47).

The structure of the bench is everywhere broadly banded, and the bands of the first variety of coal here, just as in the second bench, are confined to the lower horizons of the bench, while the bands of the sixth variety are confined to its upper horizons.

Thus, from comparison of the benches of the same name in different seam samples it follows that both the thicknesses of the benches of the same name and

the petrographic composition of them changes at each studied point of occurrence of the seam. At the same time, this variability is observed most sharply in the first bench, where, besides the variability of thickness and petrographic composition, the order of occurrence of the bright and dull coal ingredients also changes greatly; whereas in the upper part of the seam, beginning with the interbed of carbonaceous argillite that forms the boundary between the first and second benches, a decrease from bottom to top in the bright ingredients in the seam is observed. In addition, an interesting fact is the circumstance that the greatest content of bright ingredients in the first bench is observed in mine No. 3 (sample No. 1), which is our extreme western point, whereas in the second and third benches the content of bright ingredients (vitrain and the first variety) increases eastward. The latter is especially distinct when comparing the petrographic composition of the seam as a whole. Here we have a continuous and almost regular increase in the content of vitrain and the first variety of coal from sample No. 1 to sample No. 3, i.e., in the direction from west to east (Table 10).

In this same direction, i.e., from west to east, the variability of the physical and chemical properties and of the petrographic composition of the coal appears with exceptional clarity and consistency. Table 11 gives a comparative characterization of the coal varieties. From this table it is evident that coal varieties of the same name have their own petrographic as well as chemical features at each point of occurrence of the seam.

Thus, in sample No. 1 (mine No. 7), all varieties of coal are macroscopically characterized by a dense, indistinctly banded and streaky structure, a flat or uneven smoothed fracture (without sharp angular protrusions), and frequent but very fine, indistinct, discontinuous fissuring. The luster of the vitrain and of the first variety of coal here is resinous. In sample No. 2 (mine No. 5), the banded and streaky structure in the same variety of coal appears more clearly; unevenness in the fracture is expressed more sharply; the degree of fissuring increases, and the luster of the vitrain and of the first variety of coal approaches glassy. Still more distinctly, the banded and streaky structure appears in the same varieties of coal in sample No. 3 (adit No. 11). At the same time, here the degree of fissuring of the coal increases still more, and the cracks are well developed; the character of the fracture becomes rough, angular-uneven, while the vitrain and the first variety of coal here acquire a pure glassy luster.

Thus, the external appearance of the coal of seam VI Internal in the direction selected by us changes, and this change is connected by gradual transitions; that is, from sample No. 1 to sample No. 3, in the direction from west to east, the differentiation of the macropetrographic composition gradually increases, the degree of fissuring of the coal increases, the character of its fracture changes from flat to angular-uneven, and the character of the luster of the vitrain and the first variety of coal also gradually changes from resinous to glassy.

The same gradual variability of coal varieties of the same name is also observed under the microscope, and under the microscope the differentiation of the petrographic composition increases in the opposite direction, i.e., from east to west. In the coal varieties of sample No. 1, boundaries between microscopic ingredients are expressed quite clearly, whereas in these same coal varieties of sample No. 2, infrequent cases are observed of gradual transitions from structural ingredients (fusite, xylite) to cryptostructural ones (xylovitrain and vitrain), and even to structureless ones (the principal structureless mass of durite); and these gradual transitions from the structure of the ingredients to structureless ones are observed still more often in the coal of sample No. 3.

At the same time, in the eastern direction the content of vitrite and durite increases in the varieties of coal of the same name, although the degree of saturation of the durite with fusainized formations also increases. In the opposite direction, i.e., from east to west, in the same coal varieties the content of fusite and xylovitrite increases (Table 11).

In addition, under the microscope the variability in the composition of the fusainized elements of durite appears quite distinctly. Thus, in the durite of the first variety of coal of sample No. 1, among the fusainized elements there are not infrequently separate fragments of cuticles, cutinized fibers, and small grayish-brown flattened shells of microspores. In the durite of the first variety of sample No. 2, fragments of cuticles and cutinized fibers are observed only rarely in the composition of the fusainized elements; the shells of microspores are likewise rarely observed; but here the content of pale-yellow, weakly relief formations increases, apparently belonging to fragments of xylitic tissue. In the durite of the first variety of sample No. 3, neither fragments of cuticles, nor cutinized fibers, nor microspores occur at all in the composition of the fusainized and structural elements, although here the content of fragments of xylitic tissue increases greatly, and a great variety of rounded bodies of indeterminate nature appears. The latter are sometimes yellow, sometimes pale-gray in color, with a finely or coarsely cellular structure (Table III, Figs. 1, 2); more rarely these bodies are structureless or bear on their surface short furrows arranged either parallel to one another or at an angle (Table II, Fig. 4).

A. A. Luber (11, 12) assigns similar rounded bodies, studied by her in the coals of the Anzhero-Sudzhensk deposit of the Kuzbass, to fragments of plant tissue preserved in the “form of fusain, fusain-xylene, and xylovitrite.” G. Schulze (18) assigns rounded bodies with a porous and cellular structure, studied by him in the coals of the Ruhr basin, to fungal sclerotia. Yu. A. Zhemchuzhnikov (8) calls all rounded bodies bodies of “unclarified nature,” although he is inclined to suppose that they represent “resinous or stone-like formations filling the resin ducts of cycads and related plants.” It seems to us, however, that among these rounded bodies, possessing the most diverse structures and forms, there are formations of different nature, and, possibly, with special investigations all the above statements about the nature of these bodies will prove plausible.

The decrease in spore composition in the eastern direction is especially clearly revealed by maceration of the first variety of coal. By maceration of the first variety of coal of sample No. 1 (mine No. 7), various fusainized and structural elements were separated, among which the main mass consists of plant tissues, often with beautifully expressed rounded and oval cell openings. Spores and similar formations, as well as fragments of cuticles, occur more rarely.

Among the spores that do not give rise to doubt, i.e., with a clearly expressed triradiate dehiscence scar, only microspores occur, with maximum dimensions of 30–40 microns. By morphological characters our microspores are divided into two types: tuberculate spores (Table IV, Figs. 2, 6) and smooth spores (Table IV, Fig. 5). According to the classification of Zerndt (19), which he gives for macrospores (megàsporen), our tuberculate spores may, by their morphological characters, be assigned to the group apiculati, and the smooth ones to the group laevigati.

In addition to spores that do not give rise to doubt, spore-like formations (Table IV, Fig. 1), as well as formations of rounded and pear-shaped form (Table IV, Figs. 3–4), are not infrequently encountered in the products of maceration of the first variety of coal of sample No. 1. The nature of these formations still remains unclear.

Characteristics of the coal varieties of seam VI

Name of coal variety	Sample No.	Luster	Color	Structure	Fracture	Streak	Fissuring
I variety of coal	1	Resinous luster	Black	Fibrous and indistinctly banded	Flat	Black with a brownish tint	Absent
I variety of coal	2	Resinous-vitreous luster	Black	Thin-banded and striated	Flat with fine knobbiness	Black	Vertical, well expressed
I variety of coal	3	Vitreous luster	Black	Banded	Uneven	Black	Vertical, frequent, well expressed
II variety of coal	1	Weak luster (semi-lustrous)	Grayish-black	Indistinctly striated	Flat	Black with a brownish tint	Vertical, rare, dying out
II variety of coal	2	"	"	Finely striated	Uneven, finely knobby	Black	Vertical, frequent, weakly expressed
II variety of coal	3	"	"	Striated	Angular-uneven	"	Vertical, frequent
III variety of coal	1	Semi-matte	Gray	Dense, almost massive	Uneven	Black	Absent
III variety of coal	2	"	Grayish-black	Banded	"	"	Frequent, vertical
III variety of coal	3	"	Dark gray	Thin-banded	"	"	Rare, dying out
IV variety of coal	1	Matte with a glossy sheen	Gray	Dense, massive	Uneven	Grayish-black	Absent
IV variety of coal	2	Matte	"	Weakly striated	"	Black	Rare, dying out
IV variety of coal	3	"	Dark gray	Striated	"	"	Frequent, well expressed
V variety of coal	2	Matte	Black	Thin-banded	Uneven	Black	Vertical, frequent, discontinuous
VI variety of coal	1	Matte	Gray	Massive, almost homogeneous	Coarse, uneven	Grayish-brown	Absent
VI variety of coal	2	"	"	"	"	"	"
VI variety of coal	3	"	"	"	"	"	"
VII variety of coal	1	Matte	Dark gray	Massive, homogeneous	Flat-shell-like	Grayish-brown	"
VIII variety of coal	1	Matte	Dark gray	Granular	Uneven	Black-brown	Rare, oblique, filled with calcite and marcasite
VIII variety of coal	2	"	"	"	"	"	"
VIII variety of coal	3	"	"	"	"	"	"

Internal according to three seam samples

Table 11

Durite	Clarite	Vitrinite	Xylovitrinite	Xylinite	Fusinite	Durite composition: structureless mass	Durite composition: formed matter	\(W^a\)	\(A^a\)	\(V^a\)	\(A^c\)	\(V^c\)	\(V^{г-}\)
54	4	25	8	6	2	90	10	1,00	2,48	27,27	2,5	27,5	28,25
55	—	38	3	3	1	89	11	0,85	1,75	22,71	1,76	22,90	23,32
61	—	28	4	6	1	89	11	0,78	2,30	16,32	2,31	16,45	16,83
68	—	11	6	5	10	88	12	1,07	2,67	25,69	2,69	25,97	26,68
71	—	5	6	12	4	87	13	0,80	2,41	20,94	2,42	21,10	21,63
81	—	8	2	8	1	91	9	1,02	2,32	15,12	2,34	15,28	15,64
71	—	5	6	15	3	87	13	0,92	2,91	25,38	2,93	25,62	26,39
63	—	10	3	17	7	86	14	0,91	2,89	20,37	2,91	20,56	21,17
68	—	10	3	12	7	87	13	0,81	4,20	14,87	4,23	14,99	15,65
56	—	traces	3	13	27	81	19	0,93	6,43	23,23	6,49	23,44	25,07
64	—	3	2	14	18	77	23	0,81	7,38	18,98	7,44	19,07	20,67
67	—	4	1	16	11	83	17	0,87	6,07	14,75	6,13	14,88	15,85
48	—	6	2	8	37	84	16	0,75	1,77	17,91	1,78	18,04	18,37
55	—	traces	3	13	27	81	19	0,91	8,07	19,06	8,14	19,23	20,94
67	—	2	2	21	7	65	35	0,90	6,82	16,49	6,88	16,64	17,87
73	—	1	2	22	3	65	35	0,70	5,67	12,99	5,70	13,08	13,88
—	—	—	—	—	—	—	—	0,89	33,54	13,51	33,84	13,63	20,57
—	—	—	—	—	—	—	—	1,02	16,47	27,45	16,64	27,73	33,27
—	—	—	—	—	—	—	—	0,58	12,88	22,87	12,95	23,00	26,42
—	—	—	—	—	—	—	—	0,36	32,65	22,47	32,76	22,55	33,54

… and, without special study of them, one can say only that these formations are undoubtedly of plant origin and possibly related to spores.

In the products of maceration of the first variety of coal of sample No. 2 (mine No. 5), spores and similar formations occur more rarely than in the products of maceration of the first variety of coal of sample No. 1; moreover, formations of round and pear-shaped form, as well as fragments of cuticle, occur here very rarely.

In the products of maceration of the first variety of coal of sample No. 3, exclusively plant tissues and black pieces of coal are observed. Spores are almost never encountered. Only very rarely, and only upon careful examination of a large number of preparations, is it possible here to record the presence of spores, and then exclusively smooth ones (Table IV, Fig. 5); moreover, their coloration here becomes brownish-red, whereas in the first variety of coal of sample No. 1 all spores and spore-like formations are distinguished by a yellowish-greenish coloration.

Thus, in the direction from west to east, in coal varieties of the same name, a gradual smoothing of the boundaries between the ingredients is microscopically observed; i.e., with movement from west to east, gradual transitions from structural coal ingredients to structureless ones are observed more and more often. At the same time, in this same direction the content of vitrite and durite increases and the content of fusite and xylovitrite decreases; the composition of the formed elements of durite also changes toward a decrease in the content of spores, spore-like formations, and cuticles, and an increase in fragments of plant tissues and round bodies of unclear nature.

In the same direction and with the same sequence, the chemical composition of the coal also changes. From Table 11 it is evident that, in the direction from west to east, in all coal varieties of the same name there is observed a successive decrease in the yield of volatile substances. At the same time the character of the crucible coke also changes (Table 12).

The coke buttons of the first four coal varieties from sample No. 1 are the lowest; moreover, only the first variety of coal gives a swollen button; the second and third varieties give a sintered button with a melted top, while the fourth gives only a sintered coke button (Table 12, row 1). These same coal varieties from sample No. 2 give higher coke buttons. The coke button of the first coal variety becomes moderately swollen; the coke buttons of the second and third coal varieties are sintered, melted, slightly swollen; and that of the fourth coal variety is sintered and melted (Table 12, row 2). Still higher coke buttons are obtained from these same coal varieties from sample No. 3 (Table 12, row 3).

A characteristic feature of the first coal variety is the circumstance that in sample No. 1 it gives a coke button covered with a continuous layer of soot, whereas in sample No. 2 a cleaner coke button is obtained from it, the soot being observed in separate spots; and in sample No. 3 the coke button of the first coal variety is completely freed of soot and acquires a clear steel-gray color and a weak luster.

The coke buttons of the other coal varieties of the same name, the sixth and eighth, have almost the same character in all samples of the seam (Table 12). The coke button of the sixth coal variety from sample No. 1 and sample No. 2 is weakly sintered, black, and sooty. The sixth coal variety from sample No. 3 gives a coke button that is more strongly sintered, grayish-black in color, and entirely non-sooty. The eighth coal variety everywhere gives a sintered, weakly swollen coke button. Let us also note that

Table [[unclear: number]]

Serial No.	Sample No.	Probe I (No. 1)	Probe II (No. 2)	Probe III (No. 3)
1	Vitrite	specimen image	specimen image	specimen image
2	Variety I	specimen image	specimen image	specimen image
3	Variety II	specimen image	specimen image	specimen image
4	Variety III	specimen image	specimen image	specimen image
5	Variety IV	specimen image	specimen image	specimen image
6	Variety V	specimen image	specimen image	specimen image
7	Variety VI	specimen image	specimen image	specimen image
8	Variety VII	specimen image	specimen image	specimen image
9	Variety VIII	specimen image	specimen image	specimen image

the fifth variety of coal gives a coked granular coke button, and the seventh variety of coal gives a fused coke button (Table 12).

The clearest idea of the variability of the proximate composition of the coal is given by the analysis of vitrite (Table 13).

Table 13.

Name of mine	Sample Nos.	Content, in %% $W^a$	Content, in %% $A^a$	Content, in %% $V^a$	Content, in %% $V^2$	Character of the coke button
Mine No. 7	1	1.26	1.77	28.10	28.77	Swollen dark gray
Mine No. 5	2	1.01	0.86	22.40	22.82	Swollen gray
Adit No. 11	3	0.86	1.45	16.70	17.10	Swollen steel-gray

From the table presented it is evident that, in the direction from west to east, in vitrite, along with a sustained decrease in the yield of volatile substances, the content of hygroscopic moisture also decreases. The character of the crucible coke of vitrite changes in the same way as the character of the crucible coke of the first variety of coal (Table 12).

Together with the change in the proximate composition of the coal, its elemental composition also changes. The data of the elemental analysis of vitrite and of the first variety of coal show us that the carbon content both in vitrite and in the first variety of coal increases in the easterly direction, while the hydrogen content decreases in this direction (Table 14).

Table 14.

Name of ingredients	Sample Nos.	Content in %% $C$	Content in %% $H$
Vitrite	1	86.29	5.18
"	2	88.16	5.08
"	3	88.86	4.59
First variety of coal	1	86.75	5.10
"	2	86.81	5.01
"	3	88.65	4.65

Thus, the data of chemical analyses indicate that from mine No. 7 (sample No. 1) to adit No. 11 (sample No. 3), i.e., in the direction from west to east, the coal of the seam under investigation becomes more and more carbonified.

There is no doubt that the above-mentioned variability of the petrographic properties of the coal is closely dependent on the varying degree of carbonification of the coal. Hoffmann and Enker (15) indicate that, “with increasing carbonification the hardness decreases, the pieces of the mined coal become smaller and for the most part have a prismatic form,” while the decrease in hardness proceeds only up to steam-coking coals; in coals of a higher degree of carbonification, lean coals and anthracites, the hardness again increases. In addition, in studying the reflectivity (intensity of luster) of the coals of the Ruhr basin they established that the reflectivity of coals constantly increases together with an increase in their degree of carbonification. The same is indicated by Yu. A. Zhemchuzhnikov (9, 10). He states that “in the series of coals of one basin the luster of coals generally increases with the degree of carbonification, i.e., with an increase in carbon content, with a decrease in the content of hydrogen and oxygen, and also of volatile substances.”

In addition, Yu. A. Zhemchuzhnikov (8) indicates that with increasing carbonification the microscopic difference between structural and nonstruc-

...with structural ingredients is smoothed out, and that spores and cuticle, with increasing coalification, lose their outlines and become elusive for optical study.

Thus, the petrographic and chemical study of the coals of seam VI of the Vnutrennii leads us to the following series of propositions.

1. The roof and floor of the seam, their composition and structure, are identical at all sampling points.

2. The seam is everywhere divided by a parting of carbonaceous argillite and by a parting of coal of the eighth variety into three benches.

3. The workable thickness of the seam, and especially of its individual benches, differs in the various mines.

4. The quantitative content of coal varieties bearing the same name varies. At the same time, the content of bright coal (vitrain and the first variety) steadily increases from sample No. 1 to sample No. 3, i.e., in the direction from west to east.

5. The stratigraphic sequence of occurrence of the bright and dull varieties of coal in the upper part of the seam, beginning from the parting of carbonaceous argillite that separates the first bench from the second, is more or less maintained in all samples of the seam. At the same time, the lower layers of this part of the seam are everywhere enriched in bright coal, whereas the upper layers of the seam, and especially in the third bench, are very poor in it. In the first bench of the seam, however, a strong fluctuation is observed in the order of occurrence of the bright and dull varieties of coal.

6. The petrographic properties of the coal gradually change in the direction from west to east, and this variability is a consequence of increasing coalification in the same direction. In this respect, macroscopically, with the increase of coalification eastward, the following is observed:

a) an increase in the differentiation of the petrographic composition, i.e., the banded and streaky structure of the coal becomes more distinct;

b) an increase in the degree of fracturing, in connection with which, with distance eastward, the coal becomes less resistant to mechanical effects;

c) a change in the character of the coal fracture from flat to angular-uneven;

d) a change in the character of the luster of vitrain and of the first variety of coal from resinous to glassy.

Microscopically, in the same direction we record:

e) increasingly gradual transitions from structural ingredients to structureless ones;

f) an increase in the content of vitrite and durite and a decrease in the content of fusite and xylovitrinite;

g) among the shaped elements of durite, a decrease in the content of spores, spore-like formations, and cuticle, and an increase in the content of fragments of xylite and rounded bodies of unclear nature, as well as a change in the color of the spores from greenish-yellow to reddish-dark brown.

Thus, neither the floor, nor the roof, nor the general structure of the seam changes. This indicates that formation of the seam took place, in general, under identical facies conditions. If, however, a change is observed in the thickness of the workable part of the seam, and also of its individual benches, this is the result, on the one hand, of a different degree of mechanical destruction of the marginal parts of the seam (“under-roof coal”), and, on the other, of irregularities in the bottom of the swamp in which the accumulation of the original plant material took place.

The variability of the quantitative content of the bright and dull varieties of coal, as well as the unequal stratigraphic order of their occurrence in the seam, is explained, in all probability, by the fact that during the period of peat formation in different parts of the swamp, but at one and the same time, there exis...

there existed different conditions for the initial decomposition of plant material. D. White (20), Yu. A. Zhemchuzhnikov (7), and other investigators indicate that the principal factor influencing the processes of the initial decomposition of plant material is the varying degree of watering of the swamp. Thus, lustrous varieties of coal form under conditions of a strongly waterlogged swamp, where atmospheric oxygen either does not enter at all, or enters, as a result of aeration of the water cover or an influx of fresh water, in insignificant quantities, whereas dull coal—for example, fusite—forms under conditions of a dry subaerial decomposition environment.

However, despite identical conditions for the formation of varieties of coal bearing the same names, in the final result they nevertheless proved to be of different quality; i.e., in Mine No. 7 they are less coalified, while in Adit No. 11 they are more coalified.

The factors that determine coalification are usually considered to be time, pressure, and temperature. Opinions differ as to the extent to which each of these factors acts, although many investigators are inclined to suppose that tectonic pressure is the leading factor of coalification. This point of view is based on a large number of indisputable facts. In almost every coal basin, facts are observed showing a change in the degree of coalification with an increase in the intensity of folding. A characteristic example proving the correctness of this point of view is the Pennsylvania coal basin (15). In this basin the intensity of folding gradually increases from west to east. In the same direction, i.e., as the intensity of folding increases, coals of the same age and the same mode of formation show all degrees of transition from weakly coalified bituminous coal to graphite.

No less convincing examples of the influence of tectonics on the properties of coals are also provided by the Donets Basin. The studies of Mefert and Krym (13), in examining the coals of the Almaznaya and Mar’evka districts of the Donbas, established that, with an increase in the intensity of folding, in the coals of the same seams the content of volatile matter decreases and the carbon content increases.

The same dependence of coal properties on tectonics is also observed in the Kuzbass (Kemerovo, Inskaya salient) and in many other basins. It should be thought that tectonic pressure caused a change in the degree of coalification of the coal both of seam VI of the Vnutrennii, and of other seams of the Prokop’evsk district. But, lacking a sufficient amount of data on the tectonics of the Prokop’evsk district, we cannot yet assert that the intensity of folding of the productive series increases eastward. This requires additional observations. However, the available published data (1) give some possibility of assuming that toward the east the folds become more compressed (appendix No. 1). This is partly indicated also by the degree of fissuring of the coal, which, as is evident from the description of the coal, increases eastward. In the same direction the degree of disjunctive dislocation of the productive series also increases. Thus, in Mine No. 7, which works the upper parts of the Anzherian (Balakhonian) suite of the western limb of the third syncline, disjunctive disturbances are almost not observed, whereas through the field of Mine No. 5–6, which works the middle and upper subsuites of the productive series of the eastern limb of the third syncline, there passes one of the largest disjunctive disturbances of the Prokop’evsk deposit (appendix 1). Disjunctive disturbances are manifested still more strongly in the Tsentral’naya and Adit No. 11, which work the upper and middle subsuites of the productive series of the fifth and sixth synclines. Here both the limbs of the indicated folds and their closures are disturbed by a whole series of disjunctive dislocations (appendix No. 1).

CONCLUSION.

The petrographic study of seam VI of the Inner was carried out on three seam samples taken in three producing workings located in the latitudinal direction. Sample No. 1 was taken in the northern part of mine No. 7, in the face of the main drift, 157 m to the south from the northern crosscut. Sample No. 2 was taken in the southern part of mine No. 5 (mine No. 5–6 named after Comrade Voroshilov), in the face of the first parallel drift, 70 m to the south from survey point No. 2364. Sample No. 3 was taken in the northern part of adit No. 11 (continuation of the Central adit), in the face of the main drift, 12.3 m from furnace No. 24.

All samples were taken in the form of hand specimens, successively making up a column measuring 20 × 20 cm through the entire thickness of the seam.

The petrographic study was conducted separately for each sample, and the petrographic observations were checked by the simplest chemical analyses (technical and ultimate).

The results of the investigation of seam VI of the Inner are the following main conclusions.

1. The floor and roof of the seam are everywhere dense dark-gray argillite, broken by small cracks of various orientation.

2. The useful part of the seam is separated from the floor and roof by a layer of soft coal, the “underlayer.” The “underlayer” is absent in the roof of the seam in adit No. 11, and here between the roof and the seam lies a layer of black coaly argillite 0.20 m thick.

3. In the structure of the seam, three benches are everywhere distinguished. The boundary between the first and second benches is a dark-gray coaly argillite 0.04 m thick, and the boundary between the second and third benches is a bed of strongly mineralized granular coal 0.12 m thick (Table V).

4. In the composition of the coal mass of the seam, besides vitrite and fusite, eight varieties of coal have been distinguished, which macroscopically, with increasing numbers, are arranged in the order of decreasing luster and increasing uniformity of composition; microscopically—in the order of gradual decrease of the lustrous components of the coal (vitrite) and increase of the dull ones (fusite); chemically—in the order of decreasing yield of volatiles and increasing ash content.

5. The distinguished varieties of coal in the full range do not occur in any one sample. In sample No. 1 the fifth variety is absent; in sample No. 2—the seventh; and in sample No. 3—the fifth and seventh. In addition, the quantitative content of coal varieties of the same name is different in each sample. The content of vitrite and of the first variety of coal in the seam increases in an easterly direction.

6. In an easterly direction the degree of coalification of the coal increases, i.e., the carbon content increases and the content of hydrogen and volatile substances decreases. Along with this, the petrographic properties of coal varieties of the same name also change.

Macroscopically, with increasing coalification, the following is observed:

a) An increase in the differentiation of the petrographic composition, i.e., the banded and striated structure in the same coal varieties becomes more distinct.

b) An increase in the degree of fissuring of the coal.

c) A change in the character of the coal fracture from flat to angular-uneven.

d) A change in the character of the luster of vitrite and of the first variety from resinous to glassy.

Microscopically, with increasing coalification, the following is observed:

e) An increase in cases of gradual transitions from structural ingredients to structureless ones.

e) An increase in the content of vitrite and durite and a decrease in the content of xylovitrite and fusite.

f) A decrease in the content of spores, spore-like formations, and cuticles, and an increase in the content of fragments of xylite and rounded bodies of unclear origin.

g) A change in the color of the spores from greenish-yellow to reddish-dark-brown.

1. The accumulation of the initial plant material of the coal seam occurred everywhere under swamp conditions.

2. The variability in the quantitative content of coal varieties of the same name, as well as the different stratigraphic order of their occurrence in the seam, is the result of differing durations of the processes of microbiological decomposition of one and the same plant material, caused by the fact that the swamp in different areas had different degrees of water saturation.

3. The principal factor that caused the increase in coalification in the eastern direction, and at the same time the variability of its petrographic and technical properties, is the increasing degree of dislocation of the productive strata in the eastern direction.

4. The increase in the eastern direction of the intensity of folding of the productive deposits of the Prokopyevsk district, as well as the influence of disjunctive dislocations on the variability of coal properties, must be verified by special investigations, since this question is of great practical significance.

List of Literature Used

1. Zhutashov I. D., Vengrzhanovskii S. P., Adler Yu. F. and Butov P. I.—Geological-industrial description of the Prokopyevsk, Kiselevsk, and Afoninsk districts. ONTI, 1934.

2. Usov M. A.—Conference on the stratigraphy of Kuzbass. Vestnik Zap. Sib. GGTT, 1934, No. 3.

3. Usov M. A.—Tectonics of Kuzbass. Problems of Soviet Geology. 1935, No. 2.

4. Krasnikov P. F.—The principal forms of dislocations of the Prokopyevsk mine of Kuzbass. Collection on the Geology of Siberia, Tomsk, 1933.

5. Panchenko S. I.—Experimental coking of coals of the Kuznetsk Basin. 1934.

6. Zolotov S.—Properties of Prokopyevsk coals, Coal of the East, 1935, No. 4.

7. Zhemchuzhnikov Yu. A.—General geology of caustobioliths. ONTI, 1935.

8. Zhemchuzhnikov Yu. A.—Introduction to coal petrography. ONTI, 1934.

9. Zhemchuzhnikov Yu. A.—On the question of the luster and dullness of fossil coals. KhTT, 1934, No. 1.

10. Zhemchuzhnikov Yu. A.—On the study of the physical properties of coals. KhTT, 1934, No. 6.

11. Lyuber A. A.—Types of transformation of plant tissues into fossil coal. KhTT, 1934, No. 6.

12. Lyuber A. A.—Petrographic characterization of the coals of the Anzhero-Sudzhensk deposit of Kuzbass. Manuscript.

13. Mefert B. F. and Krym V. S.—Fossil coals of the Donets Basin. Issue II. Coals of the Almaznyi and Marievka districts. Leningrad, 1926.

14. Stach E.—Microscopic study of coals in transmitted light. Study of coals in reflected light. Collection of translated articles edited by Prof. Yu. A. Zhemchuzhnikov, Coal Beneficiation and Coal Petrography. ONTI, 1933.

15. Hoffmann E. and Enker A.—Coalification and its determination under the microscope. Collection of translated articles edited by Prof. Yu. A. Zhemchuzhnikov, Coal Beneficiation and Coal Petrography. 1934.

16. Schwarz H. and Laupper G.—From the charring of hay to the formation of coal in nature. 1926.

17. Stopes M.—On the Petrology of Banded Bituminous Coal. Fuel, 1935, No. 1.

18. Schulze G.—Vorkommen von Sklerotien in der Ruhrkohle. Glückauf, 1933, No. 40.

19. Zerndt F.—Megasporen als Leitfossilien des produktiven Karbons. Crakovie, 1931.

20. White D.—Role of water in the Formation of Coal. Economic Geology, 1933, No. 7.

21. Hock H. und Kühlwein F.—Gefügezusammensetzung, Inkohlung und Verkokbarkeit der Steinkohle. Glückauf, 1931, No. 38.

Explanation of the Plates

Plate I.

Fig. 1. Microstructure of durite. Fibers of plant tissue, cemented by the principal structureless mass, are clearly visible. Vertical polished section. ×100.

Fig. 2. Same as Fig. 1, but the fibers of plant tissue are less distinctly visible and become smaller. Vertical polished section. ×100.

Fig. 3. Accumulations of gray, low-relief, rounded bodies of unclear nature. Vertical polished section. ×100.

Fig. 4. Microstructure of durite. Shells of microspores, fragments of cuticle, and other shaped formations are visible. In the upper part of the photograph—an angular-rounded body of unclear nature. Vertical polished section. ×100.

Fig. 5. Microstructure of clarite. Vertical polished section. ×100.

Fig. 6. Same as Fig. 5. In the upper part of the photograph, shrinkage cracks of calcite are visible. Vertical polished section. ×100.

Plate II.

Fig. 1. Microstructure of durite. Interlacing fibers of plant tissue are clearly visible. In places, pieces of strongly gelified plant tissue have been preserved. Vertical polished section. ×100.

Fig. 2. Accumulations of gray, rounded bodies of unclear nature. In some of them a fine-cellular structure is visible. Vertical polished section. ×100.

Fig. 3. End of a xylite lens, branching into individual fibers. Vertical polished section. ×100.

Fig. 4. Microstructure of durite. Vertical polished section. ×100.

Fig. 5. Microstructure of the fifth variety of coal. Character of the arrangement of fusite. Vertical polished section. ×100.

Fig. 6. Angular and ribbon-like fragments of strongly gelified tissue. Vertical polished section. ×100.

Plate III.

Fig. 1. Fragment of cellular plant tissue, approaching in form a rounded body of unclear nature. Vertical polished section. ×100.

Fig. 2. Rounded bodies resembling fungal sclerotia, isolated by Shul’ts from coals of the Ruhr Basin. Vertical polished section. ×100.

Fig. 3. In the upper half of the photograph, fine-cellular fusite. In the lower half, accumulations of angular bodies among the principal mass of xylite. Vertical polished section. ×100.

Fig. 4. Fragments of strongly gelified plant tissue. Vertical polished section. ×100.

Fig. 5. Microstructure of fusite. Vertical polished section. ×100.

Fig. 6. Character of mineralization of the eighth variety of coal. Vertical polished section. ×100.

Plate IV.

Fig. 1. Spore-like formation. ×750.

Figs. 2–6. Microspores from the group apiculati. ×750.

Fig. 5. Microspore from the group laevigati. ×750.

Figs. 3–4. Shaped formations of indeterminate nature. ×750.

Appendix 1.

GEOLOGICAL MAP

OF THE PROKOPIEVSK DISTRICT OF KUZBASS

(after Kutashov, 1934)

Scale: 500 m — 0 — 500 m — 1000 m — 1500 m — 2000 m

Section along line CD.

Normal Section

of the Anzhero–(Balakhonka) Suite

of the Prokopievsk District

Scale: 20 m — 0 — 20 m — 40 m — 60 m

Labels visible on the stratigraphic column:

• \(H_2\)
• 3.00 — VI Inner
• 8.40 — IV Inner
• 3.40 — III Inner
• 3.20 — II Inner
• 1.80 — I Inner
• 2.00 — Characteristic…
• 9.00 — Burned
• 5.50 — Lutuginskii
• 3.15 — Prokopievsk
• 0.75 — Prokopievsk…
• 43.20 — Thick
• 0.85 — Conductor

• 3.40 — Nameless

• \(H_1\)

• 0.90 — No. 1 (Smorodina)
• 0.75 — No. 2
• 2.50 — No. 3 (Double)
• 1.00 — No. 4 (Udarnyi)
• 1.10 — No. 5 (Sadovyi)
• 1.15 — No. 6 (Pioneer)
• 1.52 — No. 7 (Juro)
• 1.40 — No. 8 (Uglovoi)
• 1.55 — No. 9 (Ostryi)
• 4.75 — No. 10 [[unclear: seam name]]
• 1.75 + 0.85 — No. 11 (Slozhnyi)

Conventional Symbols:

Symbol / designation	Meaning
\(H_3\)	Bessugan Suite
\(H_2^3\), \(H_2^2\), \(H_2^1\)	Anzhero (Balakhonka) Suite
\(H_0\)	Ostrog Suite
\(C\)	Lower Carboniferous
\(D_2\)	Middle Devonian
—	Lines of disturbances
▲▲▲	Points where lump samples were taken
■	Coal
▧	Carbonaceous argillite
dotted pattern	Sandstone
blank rectangle	Sandy shale and aleurolite
hatched pattern	Sandy-clayey shale
vertical-line pattern	Clayey shale
circles/pebbles pattern	Conglomerate

Table I.

Fig. 4.  Fig. 1.

Fig. 5.  Fig. 2.

Fig. 6.  Fig. 3.

Plate II.

Fig. 1.

Fig. 2.

Fig. 3.

Fig. 4.

Fig. 5.

Fig. 6.

Plate III.

Fig. 1.
Fig. 2.
Fig. 3.
Fig. 4.
Fig. 5.
Fig. 6.

Table IV.

1 — × 750

2 — × 750

3 — × 750

4 — × 750

5 — × 750

6 — × 750

Table V

Section-column of seam VI of the Internal Prokopyevsk mine of Kuzbass

(According to macro-petrographic investigation data.)

Mine No. 7, northern main drift, south of the northern crosscut, at 157 m.

Mine No. 5, south, I parallel drift to the south, from survey point No. 2364 at 70 m.

11th adit, northern main drift, north of point No. 24 at 12.5 m.

III bench

III bench

III bench

II bench

II bench

II bench

[[The visible page consists of three stratigraphic column diagrams with legends. No continuous body text is visible.]]

Legend

• Vitrinite
• I—variety of durite coal
• II —
• III —
• IV —
• V —
• VI —
• VII —
• VIII —
• Fusite
• Underclay
• Carbonaceous argillite
• Argillite
• Tectonic lines
• Nos. of interbeds

Legend

• Vitrinite
• I—variety of durite coal
• II —
• III —
• IV —
• V —
• VI —
• VII —
• VIII —
• Fusite
• Underclay
• Carbonaceous argillite
• Argillite
• Tectonic lines
• Nos. of interbeds

Legend

• Vitrinite
• I—variety of durite coal
• II —
• III —
• IV —
• V —
• VI —
• VII —
• VIII —
• Fusite
• Underclay
• Carbonaceous argillite
• Argillite
• Tectonic lines
• Nos. of interbeds