guide to thin section microscopy - Mineralogical Society of America

Guide to Thin Section Microscopy
Crystal shape and symmetry
Figure 3-7. Skeletal crystal shapes
A: Olivine (basalt). B, C, D: Diopside, ferriclinopyroxene and kirschsteinite (slags). E: Atoll garnet (gneiss).
F: Quartz in microcline (graphic granite).
Raith, Raase & Reinhardt – February 2012
Figure 3-8. Spherulitic, dendritic and radiating crystals
A: Chlorite spherulites (charnockite). B: Spherules of radiating zeolite showing Brewster crosses (limburgite;
+Pol). C: Spherules (obsidian, Lipari). D: Dendritic devitrification domains (basalt). E: Fan-shaped spherulitic
devitrification (obsidian, Arran). F: Microlites with dendritic, fan-shaped devitrification domains (obsidian,
Arran). G: Chalcedony (agate). H: Baryte rosettes with Brewster crosses. I: Anhydrite rosette (anhydrite,
Zechstein).
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