The most common form of calcium carbonate, calcite is known for its great variety of colors. Highly transparent rhombohedra calcites are known as optical spar, a reference to their use in polarizing filters. Single crystals such as these demonstrate the optical property of double refraction. Although it forms crystals, most calcite is massive, occurring either as limestone or marble. Well known deposits of calcite are found in Iceland, Mexico, USA, China, and Madagascar. Metaphysically, calcite is used to bring and amplify joy in one’s life.