Scheelite

Scheelite, a mineral consisting of calcium tungstate, CaWO 4. 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 a 41, the specific gravity 6o. Molybdenum is usually present, replacing an equivalent amount of tungsten; and in a greed 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 Silesia, Dragoon Mountains inArizona and elsewhere. At Trumbull in Connecticut and Kimpu-san in Japan large crystals of scheelite completely altered to wolframite have been found: those from Japan have been called " reinite."