April 23, 1915. THE COLLIERY GUARDIAN. 871 Coalmining; in Mexico.* By E. O. FORSTER BROWN. There is a large market for coke in Mexico, and the preparation of the output has been specially considered by the collieries. The author describes some of the effects of the revolution. The information on which this paper is based was obtained during the years 1908 to 1912. ’ The coal mining area was not seriously affected by the revolutions until 1913, when the position locally became acute. In that year an enormous amount of damage was done to the surface plant at a number of the collieries, the majority of which closed down. The coal production of Mexico is practically all obtained from collieries in the State of Coahuila, within 100 miles of the border of the United States of America. In 1912 there were altogether nine colliery companies, namely, three American, five Mexican, and one British. The geographical position of the coalfield is shown in fig. 1. There are no authoritative statistics of the native production, or the total coal and coke consumption; in the Republic. The following is an estimate of the coal and coke consumption in 1911 :—Gross native coal production, 1,858,996-39 metric tons; total native coal sales, 1,108,147-30 tons; total native coke sales, 250,136-29 tons; total foreign coal imported, 846,981-00 tons (in 1912, 390,158-00 tons); total foreign coke imported, 287,623-00 tons (in 1912, 284,965-00 tons); approximate total coal consumed in Mexico,! 1,955,128-30 tons; approximate total coke consumed in Mexico,! 537,759-29 tons; Mexican petroleum output, 12,629,319 barrels. The following shows the proportions of coal and coke imported in 1911 and 1912 :— Proportions of Coal and Coke Imported in 1911 and 1912. Coal. Coke. 1911. 1912. 1911. 1912. Per Per Per Per cent. cent. cent. cent. United States of America.. . 68*b7 . ... 74*40 . ... 72*30 . .. 76*41 Great Britain . 24*49 . ... 9*83 . ... 2*00 . .. 0*30 Canada . 3*43 ... 12*09 — — Australia . 1*97 — — 0*11 Germany 1*19 .7. 1T7 ‘ 24*05 ’. .. 23*18 Miscellaneous . 0’25 ... 2*51 ... 1*65 . — 100*00 . ...100*00 . ...100*00 . ..100*00 The district in which the coal basins occurs consists of fairly level country, broken by local undulations of low altitude; to the south-west, however, a range of limestone mountains of considerable altitude occurs, commencing near Lampacitos and continuing in an almost unbroken chain past Esperanzas and Musquiz far to the north of the coal district (fig. 2). Indications of volcanic agencies exist in these mountains in the form of lava flows, and low foothills of lava in places uncon- formably overlie the coal measures. The general alti- tude of the district is from 1,000 to 1,200 ft. above1 sea- level, and the climate an exceedingly dry one. The coal measures are met with in the upper cretaceous series. They are found to occur in a number of basins, or partly proved basins, the outcrops of which are often covered by shallow alluvial deposits of calcareous nature. Shales and sandstones are the pre- dominating beds in the coal measures, which are poor in coal seams. While four distinct more or less defined basins have been worked on an extensive scale, only one seam has proved of sufficient thickness and consistency to justify development. This seam, where worked, varies from 3 to 8 ft. in thickness. The other seams met with vary from a few inches to 2 ft. in thickness, and occasionally thicken locally, but not sufficiently so to justify expenditure on their development. At Agujita there are four well-defined seams, according to the bore- holes, each of which in places is of workable thickness, but the bottom and most regular seam is the only one worked. True fault throws are not common, and in this respect the field is remarkably regular. There is a marked tendency, however, for the seam to thicken and thin alternately, and to become excessively split by dirt partings in certain general directions. The various coal basins and outcrops worked are shown as far as they are proved by outcrops and boring explorations in fig. 2. A number of other basins wholly or partly proved, but not up to the present worked, are also shown. While the main seam worked or proved in the various basins is probably the same one, there is no direct evidence to prove this; while its main characteristics and especially its quality vary greatly. Sabinas Basin. The major portion of the output is obtained from the Sabinas Basin (fig. 2), which has a maximum length of about 29J miles. (48 km.) and a maximum width of about 12J miles (20 km.). Eastward of the International Railway, this basin has been worked extensively from the north-eastern outcrop by collieries now abandoned; to the south, where exposed, the seam shows indications of disturbance, and elsewhere it has not been considered worth while to attempt to prove the seam beneath the alluvial deposit. To the west of the International Railway, the Agujita, Cloete, and Rosita collieries are worked extensively on the north-eastern outcrop, while on the south-western outcrop the Palau, El Menor, and Las Esperanzas collieries are situated, the workings of the last-mentioned colliery being, however, now confined * From a paper read before the North of England Institute, of Mining and Mechanical Engineers. ! Exclusive of coal and coke consumed at collieries. to the south-eastern portion of the Las Esperanzas Basin. The basin has not been penetrated by actual under- ground developments, either by slopes or by shafts, at ■any point in excess of about 1|- miles (2 km.) from the outcrop. A number of boreholes, however, have been put down across the basin between Palau and Rosita, and indicate that the maximum depth to the main coal seam between these points does not exceed 800 ft. Further south-east, where the basin widens, the maximum depth will probably be considerably in excess of this figure. The condition and the character of the coal seam vary considerably. Between the towns of Sabinas and the south-eastern Agujita boundary the coal is too thin and dirty to be workable. It steadily improves in thickness from south-east to north-west across the Agujita pro- perty, attaining a general thickness on the north-west of 6 to 8 ft. The roof consists, on the east and in the middle of the property, of hard sandstone, and nearer the north-western boundary shale underlain by a bitu- jPORFIRIO DIAZ [CHIHUAHUA ► LAREDO rSALTH Gulf of Mexico mazatlanI .TAMPICO CEN. ^GUADALAJARA Bay of Campeche ..VERA CRUZ COATZACOALCOS REFERENCES. Scale, 288 Miles to 1 Inch o ■- c & MAPIMl\\ TORREON& “Tv VELARDENA Fig. 1 —Sketch-map of Mexico. JUAREZ RROGRt € 2 .^UER^A OE BORREGOS MEXICAN IWTERNATK ESCONDIDO ZARAGOZA ^OOKE-OVEHS^I -2 VA. ROSALES VA. OIOEDO^ . A. 39 K. 51 NAVA .COAL OUTCROP Fig. 2.—Plan of the Coahuila Coalfields. minous band containing a good deal of sulphur. This band, when allowed to fall and disintegrate, gives rise to spontaneous combustion. The seam throughout this property is closely intermixed with a number of bands of impurities. The north-westward improvement of the section is maintained in the Cloete property, and in general there is still greater improvement in the Rosita property, where, apart from local variations, the coal becomes cleaner, the bituminous sulphurous band over the coal disappears, and the bands of impurities in the seam become less. The Santa Maria, El Refugio, and Sauceda properties have not yet been developed by underground workings. Results of diamond drill borings and trial shafts, how- ever, indicate that at Santa Maria the seam, while rather ■thinner and containing a greater proportion of bands than at Rosita, is of good quality. In the El Refugio property it appears more subject to splitting; in Sauceda the upper and lower portions of the seam come together and form a good section, but again split near the Palau boundary. The coal in this basin is bituminous, while the per- centage of inherent ash is high, altogether apart from the high percentage of mechanically intermixed impuri- ties. A satisfactory coke is produced from the small, and the larger sizes of coal are used for steaming purposes. The coal becomes a little drier on the Palau than on the Agujita side of the field, as will be seen from the following table, which represents approximate average . analyses of “ mine run ” coal before washing, but after the more obvious impurities have been picked out :—■ * -i Volatile Fixed matter, carbon. Percent. Percent. Percent. Colliery. Agujita (mine run, after picking) 27*5 ... 22*5 ... 50*0 Rosita do. do. 22*0 ... 23*0 ... 55*0 Palau do. do. 19 0 ... 20 0 ... 61*0 Menor do. do. 20*0 ... 20’0 ... 60 0 The sulphur in the ash ranges from 1 to 2 per cent., and the specific gravity of the coal from 1-4 to 1-5. The natural conditions of working are on the whole favourable, and the gradients are light and little hampered by throws. Little water is met with in driving the coal, although one or two of the shafts sunk to the dip to supplement the outcrop slopes have had to contend wfith substantial feeders. Trouble with under- ground fires has been confined almost wholly to the neighbourhood of the Agujita-Cloete boundary, and is probably due to the conditions in the roof already mentioned. The roof in the majority of cases is moderate or good, and seldom really bad. By far the most important feature under this heading is firedamp. The' Agujita and Cloete mines up to the limits of their present workings (about 1,300 m. from the outcrop) have had no trouble in this respect, and work almost wholly with naked lights. At Rosita, however, a considerable quantity of firedamp is given off in working, and serious explosions have taken place in tw*o shafts, where safety lamps are used, these shafts being 164 and 223 ft. (50 and 68 m.) deep respectively. At Palau, also, a number of serious explosions have taken place both in slopes and in shafts, and the shafts sunk to the dip of the slopes have encountered strong blowers in the course of sinking and opening out. At Menor one serious explo- sion has occurred, involving a loss of 35 lives, although the workings as a whole are remarkably free from gas, due probably to the comparatively short distance over which they extend from the outcrop. Samples of coal