CUPRITE, a mineral consisting of cuprous oxide, crys tallizing in the cubic system, and forming an important ore of copper, of which it contains 88.8%. The name cuprite (from Lat. cuprum, copper) was given by W. Haidinger in 1845 ; earlier names are red copper ore and ruby copper, which at once dis tinguish this mineral from the other native copper oxide—cupric oxide—known as black copper ore or melaconite. Well-developed crystals are of common occurrence; they usually have the form of the regular octahedron, sometimes in combination with the cube and the rhombic dodecahedron. The colour is cochineal-red, and the lustre brilliant and adamantine to submetallic in char acter; crystals are often translucent, and show a crimson red colour which on prolonged exposure to light becomes dull and opaque. The streak is brownish red. Hardness 3 2 ; specific gravity 6-o; refractive index 2.85.
Compact to granular masses also occur, and there are two curious varieties—chalcotrichite and tile-ore—which require spe cial mention. Chalcotrichite (from Gr. xaXicos, copper, and 9p1 , TpcxOs hair) or "plush copper ore," is a capillary form with a rich carmine colour, and silky lustre; the delicate hairs are loosely matted together, and each one is an individual crystal enormously elongated in the direction of the edge of the cube. Tile-ore (Ger. Ziegelerz) is a soft earthy variety of a brick-red to brownish-red colour; it contains admixed limonite, and has been formed by the alteration of chalcopyrite (copper and iron sulphide).
Cuprite occurs in the reduction zone of copper bearing lodes; and is of secondary origin. Beautifully crystallized specimens were formerly found in Cornwall; they also occur in the copper mines of the Urals, in Arizona, and elsewhere. (L. J. S.)