Saturday, July 17, 2004

Cordierite

Also called �dichroite� or �iolite� blue silicate mineral that occurs as crystals or grains in igneous rocks, only as a result of contamination of the magma by aluminous sediment. Most typical, however, are its occurrences in thermally altered clayey sediments surrounding igneous intrusions and in schists and paragneisses. Precambrian deposits of the Laramie Range, Wyo., U.S., contain more than 500,000 tons

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