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Ch. 13: Olivine - Sphene

Ch. 13: Olivine - Sphene Page of 311 Ch. 13: Olivine - Sphene Text size:minus plus Restore normal size   Mail page  Print this page
280                               PRECIOUS STONES.
fracture is sub-conchoidal; it shows two cleavages, neither very distinct. The crystals belong to the orthorhombic system, and are often twinned in crossed forms ; hence the name. It occurs in crystalline rocks as a product of con­tact metamorphism, and is often associated with Garnet and Tourmaline. In chemical composition it is a conrplex silicate of iron, magnesium and aluminium. It occurs in
schist at Monte Campione in Switzerland, and with Corundum in Macon County in North Carolina, in the United States. When used as a gem it is cut en cahochon.
481. Serpentine.
It is rather questionable if the material used for the pro­duction of plaques, vases, and other similar ornamental objects should not be regarded rather as a rock than as a
Ch. 13: Olivine - Sphene Page of 311 Ch. 13: Olivine - Sphene
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