Calcite is a carbonate mineral and is the most stable form of calcium carbonate. It is one of the most common minerals on the face of the Earth, comprising about 4% by weight of the Earth's crust and is formed in many different geological environments. Pure calcium carbonate is colorless, but calcite is often colored by various impurities, including iron, magnesium, manganese, zinc or cobalt. Thus you will find calcite in a range of colors including black (extremely rare), blue, clear, green, orange, pink, red, yellow, and white.
Calcite gets its name from "chalix" the Greek word for lime. Calcite is a common constituent of sedimentary rocks, limestone in particular, much of which is formed from the shells of dead marine organisms. It is the primary mineral in metamorphic marble, occurs as a vein mineral in deposits from hot springs, and may also be found in volcanic or mantle-derived rocks. Calcite is often the primary constituent of the shells of marine organisms, like the hard parts of red algae, some sponges, and parts of the shells of some bivalves (such as oysters).
In folklore, it is said that Calcite is considered to be a powerful energy amplifier, which aids memory, is good for arts and sciences, and brings emotional balance.