calcium carbonate
Carbonate is found frequently in geologic settings. It is found as a polymorph. A polymorph is a mineral with the same chemical formula but different chemical structure. Aragonite, calcite, limestone, chalk, marble, travertine, tufa, and others all have CaCO3 as their formula but each has a slightly different chemical structure. Calcite, as calcium carbonate is commonly referred to in geology is commonly talked about in marine settings. Calcite is typically found around the warm tropic environments. This is due to its chemistry and properties. Calcite is able to precipitate in warmer shallow environments than it does under colder environments because warmer environments do not favour the dissolution of CO2. This is analogous to CO2 being dissolved in soda. When you take the cap off of a soda bottle, the CO2 rushes out. As the soda warms up, carbon dioxide is released. This same principle can be applied to calcite in the ocean. Cold water carbonates do exist at higher latitudes but have a very slow growth rate.

In tropic settings, the waters are warm and clear. Consequently, you will see many more coral in this environment than you would towards the poles where the waters are cold. Calcium carbonate contributors such as corals, algae, and microorganisms are typically found in shallow water environments because as filter feeders they require sunlight to produce calcium carbonate.