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SILLIMANITE

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Originally appearing in Volume V25, Page 109 of the 1911 Encyclopedia Britannica.
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SILLIMANITE , a See also:

rock-forming See also:mineral consisting of See also:aluminium silicate, Al2SiO5. It has the same percentage chemical See also:composition as See also:cyanite (q.v.) and See also:andalusite (q.v.), but differs from these in crystalline See also:form and See also:physical characters. It crystallizes in the orthorhombic See also:system and has the form of See also:long, slender needles without terminal planes, which are often aggregated together to form fibrous and compact masses; hence the name fibrolite, which is often employed for this See also:species. The name sillimanite is after See also:Benjamin See also:Silliman the See also:elder. There is a perfect cleavage in one direction parallel to the length of the needles. The See also:colour is greyish-See also:white or brownish, and the lustre vitreous. The hardness is 61 and the specific gravity 3.23. Sillimanite is a characteristic mineral of gneisses and crystalline See also:schists, and it is sometimes a product of contact-See also:metamorphism. It has been observed at many localities; e.g. in Bohemia (the Faserkiesel of Lindacker, 1792), with See also:corundum in the Carnatic (fibrolite of See also:comte de Bournon, 1802), See also:Chester in See also:Connecticut (sillimanite of G. T. See also:Bowen, 1824), See also:Monroe in New See also:York (" monrolite "), Bamle near Brevik in See also:Norway (" bamlite "). Pre-historic implements made of compact sillimanite are found in western See also:Europe, and have a certain resemblance to See also:jade implements.

(L. J.

End of Article: SILLIMANITE

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