The photos above (left is plane polarized light, right under crossed polarizers) show the high birefringence, twinning, and cleavage typical of calcite.
The photograph below (crossed polarizers) shows calcite replacing plagioclase.
Uniaxial -; extreme birefringence, high order colors; common polysynthetic twinning; rhombohedral cleavage; symmetrical extinction; colorless in plane polarized light.
The photos above (left is plane polarized light, right under crossed polarizers) show the high birefringence, twinning, and cleavage typical of calcite.
The photograph below (crossed polarizers) shows calcite replacing plagioclase.
Principal constituent of limestones and marbles; common alteration of other minerals and as a cement in sedimentary rocks.
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