1. Group of minerals found mostly in limestones and dolomites. Calcite (CaCO3) is the most abundant and most important. Aragonite has the same formula as calcite but is less stable and shells composed of aragonite change to calcite through geological time. Dolomite (or pearl-spar) is the magnesium-bearing carbonate commonly found as a rock-forming mineral, CaMg(CO3)2.
2. The term ‘carbonate’ is frequently used with reference to those sedimentary rocks with 95% or more of either calcite or dolomite, and is synonymous with limestone.