[ahy-uh-lahyt] 
| cordierite (kôr'dē-ə-rīt') Pronunciation Key
A light-blue to dark-blue or gray orthorhombic mineral. Cordierite is a silicate of magnesium, aluminum, and sometimes iron, and is found in granites and in metamorphic rocks that form under relatively low-pressure conditions. Chemical formula: (Mg,Fe)2Al4Si5O18. |
iolite
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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əˌlaɪt