mineralsrocks - Common Minerals and Rocks Silicates...

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Common Minerals and Rocks Silicates Ferromagnesian silicates - contain iron and/or magnesium in their structures and are usually dark in color with high specific gravity.* 1) Olivine (Mg,Fe) 2 SiO 4 a) black to olive green (most common), glassy luster, and conchoidal fracture (no cleavage). b) composed of individual tetrahedra which are bonded together by a mixture of iron and magnesium ions. c) high temperature silicate. 2) Pyroxenes (Fe,Mg)SiO 3 a) important components of the mantle* b) augite - most common pyroxene, is a black, opaque mineral with two directions of imperfect cleavage that meet at ~87 o and 93 o ; prismatic crystals. c) single chains of tetrahedra that bond together with ions of iron and magnesium. d) Dominant mineral in basalt, common rock of the oceanic crust* 3) Amphibole – hornblende (Ca,Mg) 2-3 (Mg,Fe,Al) 5 Si 6 (Si,Aal) 22 O 22 (OH) 2 horneblend e - is the most common - dark green to black with perfect cleavage at angles of 60 and 120 o , and prismatic crystals.
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mineralsrocks - Common Minerals and Rocks Silicates...

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