BLACK LEAD, GRAPIIITE, or PIX3IRAGO, a mineral consisting chiefly of carbon, but containing also more or less of alumina, silica, lime, iron, etc., to the extent of 1 to 47 per cent, apparently mixed rather than chemically combined. B. L. is the popular name, arid that by which it is generally known in the arts; graphite is that generallY preferred by mineralogists.—The name IL L., however, ought; perhaps, to regarded as an unfortunate- one, as no lead enters into the composition of the mineral. It sometimes occurs crystallized in short imbedded hexagonal prisms; but generally massive, and more or less radiated. foliated, scaly, or compact. It is of a grayish-black color, with a somewhat metallic luster, and is perfectly opaque. It is greasy to the touch, and is a. perfect conductor of electricity. It is found in primary and transi tion rocks. as in gneiss, mica-slate, quartz-rock, greenstonc, and clay-slate, and pretty abundantly in various parts of the world. It is mud] more combustible than even
anthracite. (or blind-e/md), burning with much -difficulty even before the blow-pipe, On which account it is much used for the manufacture of crucibles or " melting-pots," which withstand a great heat. These are not, however. made of mere B. L., but of B. L. in powder, mixed with half its weight of clay. B. L. is employed for making pencils (q.v.). It is also extensively employed to give a black gloss to iron grates, stoves, railings, etc., and to diminish the friction of the belts and other parts of machinery. Lately it has been suggested as a lubricating agent in the cartridges of rites, instead of lard or tallow.—Much B. L. is obtained at Borrowdale, in Cumberland; there are also great deposits in Siberia, and in :Missouri, U. S.