SCHEELITE  , a

mineral consisting of calcium tungstate, CaWO4 . It was early known as " tungsten " (meaning in Swedish, " heavy stone "), and is the mineral in which K . W . Scheele discovered tungstic acid, hence the name scheelite . Well-developed crystals are not infrequent; they usually have the form of acute tetragonal bipyramids (P in fig.); sometimes other pyramid-faces are present, and these (g and n) being developed on only one side of P indicate the parallel-faced hemihedrism of the crystals . Compact and granular masses also occur . The colour is usually yellowish white or brownish, the crystals sometimes transparent to translucent; the lustre vitreous to adamantine . The hardness is 41, the specific gravity 6•o . Molybdenum " is usually present, replacing an equivalent amount of tungsten; and in a green variety known as " cupro-scheelite " part of the calcium is replaced by copper . Scheelite usually occurs with topaz, fluor, apatite, wolframite, &c., in tin- bearing veins; and is sometimes found in association with gold . Fine crystals have been obtained from Caldbeck Fells in Cumberland, Zinnwald and Elbogen in Bohemia, Guttannen in Switzerland, the Riesengebirge in Siltsia, Dragoon Mountains inArizona and elsewhere .