1911 Encyclopædia Britannica/Benitoite

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BENITOITE, a mineral discovered in 1907 near the headwaters of the San Benito river, San Benito Co., California, and described by Prof. G. D. Louderback. It is a titano-silicate of barium (BaTiSi3O9), crystallizing in the hexagonal system, with a hardness of 6.5, and specific gravity 3.65. It may be colourless or blue, the colour varying sometimes in different parts, and passing to a deep sapphire blue. The blue variety is cut as a gem stone, and often resembles blue spinel, though its softness distinguishes it from spinel and sapphire. It is a brilliant stone, with high refractive index, and is strongly dichroic, being pale when viewed parallel to the principal axis and dark when viewed transversely.