Aragonite - Natural minerals and crystals

Aragonite is a mineral of the carbonate class, specifically a calcium carbonate (CaCO3), just like calcite. Its crystal structure is orthorhombic, different from that of calcite, making it a polymorphic form of the latter. aragonite is denser and harder than calcite. It generally appears in the form of acicular crystals, radial masses or coralloid deposits. Its color varies from white to brown, including gray, green, blue and purple. aragonite is a common mineral in low-temperature calcite deposits, such as stalactitic concretions in caves, and is also present in the shells of many marine organisms. Because of its tendency to change to calcite over time, aragonite is rarely preserved in the geologic record.