AN'THRACITE (Gk. det9paKirnc, anthrakit from cirtipa., anthrax, coal). A term used to designate the highest glade of coal, or that hav ing the highest percentage of fixed carbon, and lowest volatile contents of all the coals. It has been produced from bituminous coal by alter ation through the action of pressure and heat. These conditions are produced when rock-masses are folded up into mountains. or when beds of bi tuminous coal are approached or penetrated by an intrusion of igneous rock. In passing from the horizontal coal measures of Western Penn sylvania and Ohio to the greatly folded beds of Eastern Pennsylvania, the coal changes from bi tuminous to anthracite. At Crested Butte, Col orado, 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 un derlying the coal in that region.
Anthracite has great heating power; it burns slowly, giving off hut little smoke, nod is con sequently very clean. The average chemical com position of anthracite coal from different locali ties is as follows: 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 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 Schuylkill field (140 square miles) ; Western =Middle field (00 square miles) ; Ett'stern 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 terate 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 rre 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, Scranton, Hazelton and Pottsville are important milling, towns in the region. -\ t Crested Butte in Colorado. and near Madrid, Now :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 foot. In Europe anthracite coal is found in the Carboniferous of South It is also known in France and Belgium. What are probably the largest de posits in the world are those around Tse-Chow iu the province of Shan-si, CH'im. Baron von Eichthofen estimated that the unmined anthra cite coal ill Shan si amounted to 030,000,000,000 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 sep arated 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 chutes 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, be ing as much as 2000 to 3000 tons of marketable coal per day of ten hours.