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HYPERSTHENE , a See also: rock-forming See also:mineral belonging to the See also:group of orthorhombic pyroxenes. It differs from the other members (See also:enstatite [q.v.] and See also:bronzite) of this group in containing a considerable amount of See also:iron replacing See also:magnesium: the chemical See also:formula is (Mg,Fe)SiO3. Distinctly See also:developed crystals are rare, the mineral being usually found as foliated masses embedded in those igneous rocks—norite, hypersthene-See also:andesite, &c.—of which it forms an essential constituent. The coarsely grained See also:labradorite-hypersthene-rock (norite) of the See also:island of St See also:Paul off the See also:coast of Labrador has furnished the most typical material; and for this See also:reason the mineral has been known as " Labrador See also:hornblende " or paulite. The See also:colour is brownish-See also:black, and the plbochrism strong; the hardness is 6, and the specific gravity 3.4-3.5. On certain surfaces it displays a brilliant See also:copper-red metallic sheen or See also:Schiller; which has the same origin as the bronzy sheen of bronzite (q.v.), but is even more pronounced. Like bronzite, it is sometimes cut and polished for ornamental purposes. (L. J.
End of Article: HYPERSTHENE
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