lowest volatile contents of all the coals. It has been produced from bituminous coal by alteration through the action of pressure and heat. These conditions are produced when rock-masses are folded up into mountains, or when beds of bituminous coal are approached or penetrated by an intrusion of igneous rook. In passing from the horizontal coal measures of Western Pennsylvania and Ohio to the greatly folded beds of Eastern Pennsylvania, the coal changes from bituminous to anthracite. At Crested Butte, Colorado, beds of bituminous coal are found to change to anthracite in those portions of the mass which are in close proximity to basaltic rocks that have been intruded into the beds underlying the coal in that region.
Anthracite has great heating power; it burns slowly, giving off but little smoke, and is consequently very clean. The average chemical composition of anthracite coal from different localities is as follows:
Fixed Carbon Mammoth vein, Pa. Anthracite, Col. . . . Madrid, N. Mex. . . . Shan-si, China Vola- tile Water Matter .38 3.08 4.12 82.33 9.96 .81 93.02 1.04 .16 Aeh Sul- piiur .92 .50 6.90 1.06 5.78 .117 .74 5..55 1.55 10.15 .25
Anthracite is found at a number of widely sep- arated localities; but the areas underlain by it are seldom large because its formation is depend- ent on local conditions. In the United States it is found in Eastern Pennsylvania, where it forms several detached areas aggregating about 470 square miles. These fields are known as the Southern or Schuyllkill field (140 square miles); Western Middle field (90 square miles); Eastern Middle field (40 square miles); Northern or Wyoming (200 square miles); Loyalsock or Western Northern. The coals all belong to the Middle Carboniferous or Pennsylvanian Series, at the base of which is a hard bed known as the Pottsville conglomerate. After beds of the Coal-measures had been folded into basins, the presence of the outcropping ledges of con- glomerate along the crests of the ridges pro- tected the coal beds to a large extent and have kept them from being entirely worn away by weathering and erosion. The total number of workable anthracite seams is about 15, but sever- al others are also known. The aggregate thickness of the beds increases from west to east; the best known is the Mammoth Bed, which in places may exceed 100 feet in thickness, while elsewhere it may split up into several beds separated by lay- ers of shale. Wilkes-Barre, Seranton, Hazelton and Pottsville are important mining towns in the region. At Crested Butte in Colorado, and near Madrid, New Mexico, anthracite is found in beds of Upper Cretaceous age. the formation of the anthracite in each case being due to igneous in- trusions. Indeed, at the latter locality, the change from bituminous to anthracite coal takes place within a distance of 2000 feet. In Europe anthracite coal is found in the Carboniferous of South Wales. It is also known in France and Belgium. What are probably the largest de- posits in the world are those around Tse-Chow in the province of Shan-si. China. Baron von Richthofen estimated that the unmined anthra- cite coal in Shan-si amounted to 630,000,000,000 tons, and that the area was greater than that of Pennsylvania.
Anthracite coal, after mining, goes through a crushing and sorting process in coal-breakers, in which the machinery consists of crushing-rolls and screens. In this treatment the coal is separated into the different sizes given below, and particles of slate are eliminated. Much of the latter is separated by screens having the bars set at an angle, so that when a mixture of coal and slate passes over them the slate particles, owing to their thinness, slip through, while the coal passes by. Pieces of mixed coal and slate are known as bone-coal, and are picked out by boys when the smaller sizes of coal come down the shutes from the screens. Recently, wet methods of separation of slate and coal, by means of jigs (q.v.) have been adopted with great success. The capacity of some breakers is very large, being as much as 2000 to 3000 tons of marketable coal per day of ten hours.
The following sizes are shipped from the breaker:
Broken, or Grate coal, which passes through 4-inch mesh, but not through 2.5-inch mesh.
Egg coal, which passes through 2.5-inch mesh, but not through 1.75-inch mesh.
Stove coal, which passes through 1.75-inch mesh, but not through 1.25-inch mesh.
Chestnut coal, which passes through 1.25-inch mesh, but not through .75-inch mesh.
Pea coal, which passes through .75-inch mesh, but not through .50-inch mesh.
Buckwheat coal, which passes through .50-inch mesh, but not through .25-inch mesh.
Very coarse lumps are known as "steamboat coal," and some finer sizes are at times separated into two kinds, which are known as rice and flax- seed. The finest refuse from the breakers and mines is known as "culm, and has been a source of much concern since, through being considered as waste, it has been allowed to collect in enor- mous heaps, forming a marked topographic fea- ture of the anthracite regions. Owing to the fine- ness of this material, it was for some years found difficult to burn it in grates, as it packed and hin- dered the entrance of air. In recent years meth- ods of utilization for culm have been found, and many of the banks have been worked over and the coarser particles washed out and sized. It can be burned in specially constructed grates, or can be mixed with tar and pressed into briquettes for use with the ordinary grate. Another impor- tant use is for filling in abandoned or partially worked-out mines, which is done by washing the culm down through a pipe into the mine, where it settles into a compact mass.
In the trade, anthracite is sometimes classed as follows: Free burning, white ash, hard white ash, Wyoming red ash, Lehigh red ash, Shamokin, Lykens Valley red ash, Schuylkill red ash, Trevorton, Lorberry red ash, and Bernice white ash. The hard white ash commands the best price.
The production of anthracite coal in Pennsylvania from 1895 to 1900 was as follows:
Year Total product Value at MineB .verai:e price per tun No. employed .vernffe Xo.daya worked ISftl ISflfi 1897 IS'.IR 18!)!) 1900 ,78.5,122 .53.3.287 .974.715 .0(53,076
- ),M4,(M7 ,
,231..3S3 .019,272 8,178,651 7n,.301.9o4 75.414. .5:i7 88,142,1.30 85,757,851 $1.72 1.85 1.85 1.75 1.80 1.85 ,917 148,991 149..W7 14.'i.l8t 139,008 144,208 fi 174 1.50 1.53 ITS 186
