BLACK-Wad, an ore of manganese, of which, according to Klaproth, it contains sixty-eight per cent. It is of a brown or black colour, opaque, very sectile, and soils the fingers on being touched. Though its specific gravity is as high as 3.706, it appears very light when lifted in the hand, but imbibes water with violence, and is no sooner immersed in it than it sinks. Mixed with linseed oil it undergoes a spontaneous combustion. The localities of black-wad are particularly Devonshire and Cornwall, where it occurs accompanying other ores of manganese. The dendritic delineations, often so beautiful upon limestone, steatite, and other substances, are supposed to derive their colouring matter from this mineral.