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GREENOCKITE
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GREENOCKITE , a rare See also:mineral composed of See also:cadmium sulphide, CdS, occurring as small, brilliant, See also:honey-yellow crystals or as a See also:canary-yellow See also:powder. Crystals are hexagonal with See also:hemimorphic development, being differently terminated at the two ends. The faces of the hexagonal See also:prism and of the numerous hexagonal pyramids are deeply striated horizontally. The crystals are translucent to transparent, and have an adamantine to resinous lustre; hardness 3-31; specific gravity 4.9. Crystals have been found only in See also:Scotland, at one or two places in the neighbourhood of See also:Glasgow, where they occur singly on See also:prehnite in the amygdaloidal cavities of basaltic igneous rocks—a rather unusual mode of occurrence for a metallic sulphide. The first, and largest crystal (about 1 in. across) was found, about the See also:year 181o, in the See also:dolerite See also:quarry at See also:Bowling in See also:Dumbartonshire, but this was thought to be See also:blende. A larger number of crystals, but of smaller See also:size, were found in 184o during the cutting of the Bishopton See also:tunnel on the Glasgow & See also:Greenock railway; they were detected by See also:Lord Greenock, afterwards the and See also:earl of See also:Cathcart, after whom the mineral was named. A third locality is the Boyleston quarry near See also:Barrhead. At all other localities—Przibram in Bohemia, Laurion in See also:Greece, See also:Joplin in See also:Missouri, &c. —the mineral is represented only as a powder dusted over the See also:surface of See also:zinc minerals, especially blende and See also:calamine, which contain a small amount of cadmium replacing zinc. Isomorphous with greenockite is the hexagonal zinc sulphide (ZnS) known as wurtzite. Both minerals have been prepared artificially, and are not uncommon as See also:furnace products. Previous to the See also:recent See also:discovery in See also:Sardinia of cadmium See also:oxide as small octahedral crystals, greenockite was the only known mineral containing cadmium as an essential constituent. (L. J. S.). Additional information and CommentsThere are no comments yet for this article.
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