A sodium-bearing pyroxene of highly-alkaline igneous rocks. Mostly identified by its deep green color. May show characteristic 87-93 degree pyroxene cleavage.
The deep color pretty much dominates the interference colors.
Below is acmite in plane-polarixed light. Note the near right-angle pyroxene cleavage in the central grain. Pyroxene cleavage this good is actually fairly uncommon, and much more often seen in thin section than hand specimen.
Same field in crossed polarizers. The deep green color still pretty much dominates, though some grains with red interference colors shift to orange or yellow, a blend of interference color and natural color. Note also the lath-like plagioclase feldspar crystals
Created 10 Oct 1997, Last Update 16 December 1999
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