922g Optical Calcite Freeform TC1985 slices is a very vesicular volcanic

is a very vesicular volcanic (igneous) rock that is typically dark colored

Hyalite doesn't have the same internal structure of tiny spheres of silicon dioxide that cause precious opals to have brilliant displays of color

analytical side of our brains

This nodule of Polish flint has been sliced and polished to display the wonderful banding inside

922g Optical Calcite Freeform TC1985 slices is a very vesicular volcanic922g Optical Calcite Freeform Approx. Dimensions: 4x3x3 inches Approx. Weight: 922 grams Locality: Maharashtra, India Optical calcite is also referred to as Iceland Spar because of its first discovery in Eskifjord, Iceland. It is typically colorless, and exhibits the optical phenomenon of double refraction where an object viewed through the calcite will appear doubled. Double refraction, or birefraction, is also called birefringence and is also