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Ch. 25: Other Semi-Precious Stones

Ch. 25: Other Semi-Precious Stones Page of 187 Ch. 25: Other Semi-Precious Stones Text size:minus plus Restore normal size   Mail page  Print this page
cut cabochon for use in pins, or beads or buttons. Triclinic and occurs in crystals or compact masses. Hardness = 5-5. Specific gravity =. Colour i rose-red or
pink; also yellow, green or brown. Lustre: Vitreous to pearly. Mean refractive index =. Composition: MnSiOa. It is found in many manganese mines in the Central Provinces, Central India, Bombay and Madras. It occurs in a massive form. Colour: brownish-red, flesh-red or rose-pink. It is also obtained from the Ural Mountains and from Franklin, New Jersey.
19.    Serpentine.—It is a hydrated silicate of magnesia with iron. It is used for ornamental purposes and cut cabochon for gems. Monoclinic but never occurs in crystals and forms platy or fibrous masses. Hardness =to 4. Specific gravity = . Colour: various shades of green, also yellowish, greyish, reddish, brownish or black. Lustre: dull, resinous, greasy or waxy. Feel is smooth to greasy or waxy. Mean refractive index variable,to
Precious serpentine is translucent and green or yellow in colour. Varieties:—Bowenite—granular and re­sembles jade; Williamsite—blackish green; Verde antique— massive green; Chrysotile—fibrous. Good material is found in Sweden, Scotland, Silesia, Saxony, Rhode Island, Vermont, Massachusetts, Pennsylvania and California. Some material of attractive colour is found in the asbestos mines near Pulivendla, Cuddapah district, Madras.
20.    Smithsonite.—Though usually unattractive, those of yellow-green or blue may be cut cabochon or used for ornamentation. Composition— It is formed by the alteration of zinc sulphide and occurs in limestone and dolomite.
21.    Sodalite is polished as an ornamental stone or sometimes cut cabochon. It is deep blue in colour and resembles lazurite. Cubic. Isotropic. Hardness = 5 to 6. Specific gravity = 2-24. It is found in the Ural Mountains
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Ch. 25: Other Semi-Precious Stones Page of 187 Ch. 25: Other Semi-Precious Stones
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