1moderatetohighpos minindex15221696

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Unformatted text preview: 2(Mg,Fe)3AlSi3O10(OH,O,F)2 optic biaxial neg Too ­Vee 0 ­ 25 ¡ relief.1 moderate to high pos min. index 1.522 / 1.696 color brown, green, orange pleochroism yes birefringence.1 0.030 ­ 0.070 cleavage yes {{ easily seen elongation yes yesalong cleavage extinction parallel, nearly parallel angle 0 ­ 9¡ alteration commonly alters to chlorite and clay minerals habit.1 columnar, tabular, platy occurence metamorphic (contact, low to high grade), igneous TwoV 1 relief 2 3 pleochroism.2 tan, green, brown birefringence 9 12 13 cleavage.2 {001} perfect, controls fragment orientation...
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This document was uploaded on 02/25/2014.

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