Calcite

Calcite is a widespread mineral, mainly calcium carbonate (CaCO3), found in sedimentary rocks like limestone. It varies in color from clear and white to yellow, green, and blue. Recognizable by its rhombohedral cleavage and reaction with dilute hydrochloric acid, calcite is valued for geology, optics, construction, and as a collectible mineral.

White flat Rhombohedral an twinned Calcite on light orange Aragonite.