ANTHRACITE, a variety of coal distin guished from other coals by its high propor tion of carbon and small quantity of volatile matter. It has a conchoidal fracture, bright lustre, dense black color and superior hardness. The percentage of carbon is variable, ranging from a minimum of about 80 per cent to a max imum of 95 per cent. Anthracite grades by imperceptible stages into bituminous coal, from which it has been produced by the action of heat or intense pressure. Semi-anthracite and semi-bituminous are intermediate grades. The coal-seams of eastern Pennsylvania are in cluded in a series of strata which have been compressed and thrown into folds, while west ward in the bituminous fields of Pennsylvania and Ohio the strata lie nearly horizontal. Beds of bituminous coal are frequently observed to grade into anthracite in the vicinity of igneous intrusions, as at Crested Butte, Cola, and near Sante Fe, N. M. Where the heat has been very intense, however, the volatile matter is entirely driven off and graphite is formed.
Anthracite occurs in extensive deposits in many parts of the world. The most productive deposits are those of eastern Pennsylvania which occur in several detached fields, located as follows: The Northern field, extending through the middle of Luzerne and Lackawanna counties ; the Eastern Middle, between the Le high River and Catawissa Creek; the Western Middle, between the eastern headwaters of the Little Schuylkill River and the Susquehanna; and the Southern, or Pottsville, field, extending from the Lehigh River at Mauch Chunk south west to near the Susquehanna River. These fields comprise an area of 472 square miles and are classed under three general divisions, namely, Wyoming, Lehigh and Schuylkill re gions. The Bernice field in Sullivan County produces a semi-anthracite coal and is some times included with the anthracite fields. The strata with the beds of coal have been upturned and the outcropping edges subjected to long continued erosion. The most important and persistent seam is the Mammoth, which in the Eastern Middle field has a thickness of from 60 to 90 feet and is over 100 feet thick in parts of the Southern and Western Middle fields. Al together the workable seams number 15 or more, with a total thickness (increasing from west to east) ranging from 70 to 150 feet. The anthracite fields of Colorado and New Mexico are of much less importance. In foreign coun tries anthracite is mined in South Wales, Ire land, Belgium, France, Westphalia and Russia, and it is known to occur in very large deposits in the province of Shan-Si, China. In the south Wales field only the northern portion yields an thracite, the rest of the output being semi-bitu minous and bituminous coals.
Owing to its cleanliness and freedom from smoke anthracite is especially suited for house hold fuel; for steaming and metallurgical pur poses it is inferior to bituminous coal. It ignites
with difficulty and burns slowly with little flame, giving out intense heat. The amount of ash is small ranging from 15 per cent to 6 or 7 per cent. the color of the ash is sometimes used as a basis of classification in trade, as in Pennsylvania anthracites, which are denomi nated white-ash and red-ash coals. But the color depends entirely upon the amount of iron pres ent and is no criterion of the value. The fol lowing analyses show the relative proportions of fixed carbon, volatile matter, ash, etc., in va rious anthracites: The preparation of anthracite for the market consists in freeing it from slate and dust and sorting it into suitable sizes. Owing to the practical absence of volatile matter, anthracite will not burn unless the lumps are of fairly uni form size. When hoisted from the mine it is firstpassed over a screen which allows most of the fine coal to pass through. The lump coal is .then sorted for the purpose of removing the shale and slate, and the pure material is crushed between rolls and screened into the market sizes. In the United States the sizes generally recognized are the following: Broken or grate, which passes through a screen of 4-inch mesh but not through 2.5-inch mesh; egg, 2.5-inch 1.75—inch; stove, 1.75—inch-1.25—inch chestnut, 1.25-inch-0.75-inch; pea, 0.75-inch-0.50-inch; and buckwheat, 0.50-inch-025-inch. Larger sizes than the above are known as lump and steam boat, and smaller sizes as rice, mustard-seed, etc. The sizes from broken to chestnut, inclu sive, are known as the domestic prepared sizes and constitute at present about 60 per cent of the output. The waste or fine coal which com monly amounts to as much as 10 per cent of the material mined is known as culm. Immense heaps of this fine coal have accumulated at the mines, but with the improved processes of screening and separation much of it is now saved and sold to manufacturing plants.
The growth of the anthracite mining indus try in the United States has been very rapid. There are records showing that Pennsylvania anthracite was used for fuel as early as 1768, but mining was not carried on to any extent until about 1820. The growth of the industry from this time to the close of the century is shown in the following table: Short tons Short tons 1820 365 1870 15,664,275 1830 215,272 1880 28.649,812 1840 967.108 1890 46.468,641 1850 4,138,164 1900 57,367.915 1860 8.115.842 1910 84,485,236 The production and value of Pennsylvania anthracite during the period 1911-15 were as follows: Almost the entire output of anthracite is consumed as domestic fuel. A small portion is used for manufacturing purposes in large cities, but it is being gradually superseded for this purpose by the cheaper bituminous coal. See Cowl..