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VESUVIANITE

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Originally appearing in Volume V27, Page 1063 of the 1911 Encyclopedia Britannica.
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VESUVIANITE , a See also:

rock-forming See also:mineral of complex com- position. It is a basic See also:calcium and See also:aluminium silicate See also:con- aining small amounts of See also:iron, See also:magnesium, See also:water, See also:fluorine, etc., and sometimes See also:boron; the ap- proximate See also:formula is H2Ca6(Al,Fe)aSi5O18. It crystallizes in the tetragonal See also:system, but often exhibits See also:optical anomalies, and the optical sign varies from See also:positive to negative. Well-devel- oped crystals are of frequent occurrence. They usually have the See also:form of four- or eight-sided prisms terminated by the basal planes (c) and See also:pyramid-planes (p in fig.); the See also:prism-planes are vertically striated and the basal planes smooth and See also:bright. Crystals are transparent to translucent, vitreous in lustre and vary in See also:colour from See also:brown to See also:green; a See also:sky-See also:blue variety, called cyprine, owes its colour to the presence of a trace of See also:copper. The specific gravity is 3.4 and the hardness 62. The name vesuvianite was given by A. G. See also:Werner in 1795, because See also:fine crystals of the mineral are found at See also:Vesuvius; these are brown in colour and occur in the ejected See also:limestone blocks of See also:Monte Somma. Several other names have been applied to this See also:species, one of which, idocrase of R. J.

See also:

Hauy (1796), is now in See also:common use. Vesuvianite is typically a mineral of contact-metamorphic origin, occurring most frequently in crystalline limestones at their contact with igneous rock-masses; it also occurs in See also:serpentine, See also:chlorite-schist and See also:gneiss, and is usually associated with See also:garnet, See also:diopside, See also:wollastonite, &c. Localities which have yielded fine crystallized specimens are the See also:Ala valley near See also:Turin, See also:Piedmont, Monte Somma (Vesuvius), Monzoni in the Fassa valley, See also:Tirol, Achmatovsk near Zlatonst in the Urals, the See also:River Wilui See also:district near See also:Lake See also:Baikal in See also:Siberia (" wiluite "), See also:Christiansand in See also:Norway, &c. When found in transparent crystals of a See also:good green or brown colour it is occasionally cut as a See also:gem-See also:stone. A compact variety, closely resembling See also:jade in See also:appearance, has been used as an ornamental stone. (L. J.

End of Article: VESUVIANITE

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