Calcite gets its name from the Greek word "chalix", which means lime. According to mineral.galleries.com, Calcite, or calcium carbonate, makes up about 4% by weight of the earth's crust. Calcite is the stable form of calcium carbonate and is one of the most widely distributed minerals on the face of the earth. Quartz, or silicon dioxide is another.
Calcite has a Hardness of 3 on the Mohs hardness scale. Specific gravity of 2.72. Streak: White. calcite is brittle and is often florescent. Calcite is a common constituent of sedimentary rocks, limestone in particular. Calcite is also the primary mineral in the metamorphic rock, marble. Calcite becomes marble from the heat and pressure of metamorphic events. Calcite forms as a vein mineral in hot springs and occurs in caverns as stalactites and stalagmites.Calcite is the primary mineral in shells of marine organisms; some sponges, corals, the hard parts of algae, brachiopods, by-valves such as oysters, echinoids, and most bryozoa.
Although being a very common mineral, its extraordinary diversity of crystal formations and a wide array of colors makes Calcite very popular with mineral collectors. There are more than 300 crystal forms identified in calcite and these forms can combine to produce the thousand different crystal variations.