WITHERITE, a mineral consisting of barium carbonate crystallizing in the orthorhombic system, and named after W. Withering, who in 1784 recognized it to be chemically distinct from barytes. The crystals are invariably twinned to gether in groups of three, giving rise to pseudo-hexagonal forms somewhat resembling bipyramidal crystals of quartz; the faces are usually rough and striated horizontally. The colour is dull white or sometimes greyish, the hardness is 3.5 and specific
gravity 4.3. The mineral occurs in veins of lead ore near Hex ham in Northumberland, Alston in Cumberland, Anglezark, near Chorley, Lancs., and a few other localities. It is the chief source of barium salts, and is mined in considerable amounts in North umberland. It is used for the preparation of rat poison, in the manufacture of glass and porcelain, and formerly for refining sugar. (L. J. S.)