Carbonate minerals are classified based on their chemical composition and crystal structure, forming distinct groups that exhibit unique characteristics. Anhydrous carbonates are those lacking water in their crystal structure. Among these, the Aragonite Group is orthorhombic, characterized by its distinct crystallography and common occurrence in marine environments as calcium carbonate (CaCO₃). The Calcite Group, also primarily composed of calcium carbonate, differs by its trigonal crystal system, notable for forming rhombohedral crystals and its widespread presence in sedimentary rocks and limestone formations. Another subgroup within anhydrous carbonates is the Dolomite Group, which includes minerals like dolomite (CaMg(CO₃)₂) with a trigonal crystal structure. These minerals are distinguished by their complex formulas incorporating additional elements, leading to varied chemical properties and geological significance.

In contrast, Carbonates with Hydroxyl or Halogen incorporate hydroxide or halogen ions into their structure, creating unique mineral varieties often with a monoclinic crystal system. An example is malachite (Cu₂CO₃(OH)₂), known for its vibrant green color and use as a copper ore. Hydrated Carbonates contain water molecules within their crystal lattice, affecting their stability and physical properties. Azurite (Cu₃(CO₃)₂(OH)₂), a well-known hydrated carbonate, is prized for its deep blue color and serves as both an ore of copper and a gemstone. These classifications reflect the diverse nature of carbonate minerals, highlighting their varied structural and compositional characteristics that influence their geological and practical applications.