Optical Mineralogy Andalusite chiastolite
Andalusite in plane polarized and cross polarized light, showing chiastolite cross, moderate relief, and low interference colors. Matrix contains fine-grained biotite and quartz.
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Optical Mineralogy pleochroism parallel extinction orthopyroxene
Volcanic orthopyroxene in plane-polarized and cross-polarized light, showing subtle pink-green pleochroism (plane-polarized light) and parallel extinction (cross-polarized light).
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Crystallography Mineralogy: Lecture 6. Polymorphism and Crystal habit http://www.world-earthquakes.com
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Crystallography Mineralogy: Lecture 23. Phyllosilicates 1 - Mica, Chlorite and Talc
http://www.world-earthquakes.com
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