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ENSTATITE

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Originally appearing in Volume V09, Page 654 of the 1911 Encyclopedia Britannica.
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ENSTATITE , a See also:

rock-forming See also:mineral belonging to the See also:group of orthorhombic pyroxenes. It is a See also:magnesium metasilicate, MgSiO3, often with a little See also:iron replacing the magnesium: as the iron increases in amount there is a transition to See also:bronzite (q.v.), and with still more iron to See also:hypersthene (q.v.). Bronzite and hypersthene were known See also:long before enstatite, which was first described by G. A. See also:Kenngott in 1855, and named from ivgTaTi S, " an opponent," because the mineral is almost in-fusible before the See also:blowpipe: the material he described consisted of imperfect prismatic crystals, previously thought to be See also:scapolite, from the See also:serpentine of See also:Mount Zdjar near Schonberg in See also:Moravia. Crystals suitable for goniometric measurement were later found in the See also:meteorite which See also:fell at Breitenhach in the See also:Erzgebirge, Bohemia. Large crystals, a See also:foot in length and mostly altered to steatite, were found in 1874 in the See also:apatite See also:veins traversing See also:mica-schist and See also:hornblende-schist at the apatite mine of Kjorrestad, near Brevig in See also:southern See also:Norway. Isolated crystals are of rare occurrence, the mineral being usually found as an essential constituent of igneous rocks; either as irregular masses in plutonic rocks (norite, See also:peridotite, See also:pyroxenite, &c.) and the serpentines which have resulted by their alteration, or as small idiomorphic crystals in volcanic rocks (See also:trachyte, See also:andesite). It is also a See also:common constituent of meteoric stones, forming with See also:olivine the bulk of the material: here it often forms small spherical masses, or chondrules, with an See also:internal radiated structure. Enstatite and the other orthorhombic pyroxenes are distinguished from those of the See also:monoclinic See also:series by their See also:optical characters, viz. straight extinction, much weaker See also:double See also:refraction and stronger pleochroism: they have prismatic cleavages (with an See also:angle of S8° 16') as well as planes of parting parallel to the planes of symmetry in the ,See also:prism-See also:zone. Enstatite is See also:white, greenish or See also:brown in See also:colour; its hardness is 51, and sp. gr. 3.2—3.3.

(L. J.

End of Article: ENSTATITE

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