Scheelite
SCHEELITE, a mineral consisting of calcium tungstate, CaWXX. 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 ) 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 45, the specific gravity 6-0. 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, etc., in tinbearing 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."
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)
