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CUPRITE
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CUPRITE , a See also:mineral consisting of cuprous See also:oxide, Cu2O, crystallizing in the cubic See also:system, and forming an important ore of See also:copper, of which See also:element cuprite contains 88.8%. The name cuprite (from See also:Lat. cuprum, copper) was given by W. See also:Haidinger in 1845; earlier names are red copper ore and See also:ruby copper, which at once distinguish this mineral from the other native copper oxide—cupric oxide—known as See also:black copper ore or See also:melaconite. Well-See also:developed crystals are of See also:common occurrence; they usually have the See also:form of the See also:regular See also:octahedron, sometimes in See also:combination with the .See also:cube and the rhombic See also:dodecahedron. A few Cornish crystals have been observed with faces of a form {hkl} known as the pentagonal icositetrahedron,since it is bounded by twenty-four irregular pentagons. In this class of cubic crystals there are no planes or centre of symmetry, but the full number (thirteen) of axes of symmetry; it is known as the See also:trapezohedral hemihedral class, and cuprite affords the best example of this type of symmetry. The See also:etching figures do not, however, conform to this See also:lower degree of symmetry, nor do crystals of cuprite rotate the See also:plane of polarization of plane-polarized See also:light. The See also:colour of the mineral is See also:cochineal-red, and the lustre brilliant and adamantine to sub-metallic in See also:character; crystals are often translucent, and show a See also:crimson-red colour by transmitted light. On prolonged exposure to light the crystals become dull and opaque. The streak is brownish-red. Hardness 31; specific gravity 6•o; refractive See also:index 2.85. Compact to granular masses also occur, and there are two curious varieties-chalcotrichite and See also:tile-ore—which require See also:special mention. Chalcotrichite (from Gr. xaAnos, copper, and 0p(E, 'rptx6s, See also:hair) or " See also:plush copper ore " is a capillary form with a See also:rich See also: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 See also:diagonal or the edge of the cube. Tile-ore (Ger. Ziegelerz) is a soft earthy variety of a See also:brick-red to brownish-red colour; it contains ad-mixed See also:limonite, and has been formed by the alteration of chalcopyrite (copper and See also:iron sulphide).
Cuprite occurs in the upper See also:part of copper-bearing lodes, and is of secondary origin, having been produced by the alteration of copper sulphides. Beautifully crystallized specimens were formerly found in Wheal Gorland and Wheal Unity at Gwennap, and in Wheal See also:Phoenix near See also:Liskeard in See also:Cornwall; they also occur in the copper mines of the Urals, and in See also:Arizona. Isolated crystals bounded by faces on all sides, and an See also:inch or more in See also:diameter, are found embedded in a soft See also: Additional information and CommentsThere are no comments yet for this article.
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