Black Lead
GRAPHITE, or 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. Black lead is the popular name, and that by which it is generally known in the arts, though no lead enters into the composition of the mineral; graphite is that generally preferred by mineralogists. It sometimes occurs crystallized in flat hexagonal tables; 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 a black and shining streak, and is perfectly opaque. It is greasy to the touch, and is a perfect conductor of electricity. It occurs in beds and masses, laminæ or scales in the schistose rocks (gneiss, mica schist, clay slate, etc.), and is sometimes in such abundance as to give its name to the schist (graphite schist) in which it appears. Thick, vein-like masses of black lead are met with in Siberia, Spain, Canada, New Brunswick, United States, Ceylon, and elsewhere. It is far more incombustible than even anthracite (or blind coal), on which account it is much used for the manufacture of crucibles or melting-pots. These are half clay and black lead. Black lead is employed BLACKLEG for making pencils. It is also extensively employed to give a black gloss to iron grates, railings, etc., and to diminish the friction of belts, machinery, and rifle cartridges.