|dichroite, Also called: iolite a grey or violet-blue dichroic mineral that consists of magnesium aluminium iron silicate in orthorhombic crystalline form and is found in metamorphic rocks. Formula: (Mg,Fe)2AL4Si5O18.nH2O|
|[C19: named after Pierre L. A. Cordier (1777--1861), French geologist who described it]|
blue silicate mineral that occurs as crystals or grains in igneous rocks. It typically occurs in thermally altered clay-rich sediments surrounding igneous intrusions and in schists and paragneisses. Precambrian deposits of the Laramie Range, Wyo., U.S., contain more than 500,000 tons of cordierite. Cordierite is sometimes called dichroite because of its marked pleochroism (different coloured light is transmitted in different directions). For chemical formula and detailed physical properties, see silicate mineral (table)
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