Knowra Calcite Calcite Calcite is a crystalline form of calcium carbonate (CaCO₃) and a major constituent of limestone and marble. Its trigonal crystals react readily with dilute acids and split light into two rays.
Calcium carbonate : Calcium carbonate is an inorganic compound, CaCO₃, found in minerals, shells, and geological deposits. Calcite is one crystalline form of this compound.
Birefringence : Birefringence is the splitting of light into rays that travel at different speeds through an anisotropic material. Calcite’s strong birefringence produces a conspicuous double image.
Limestone : Limestone is a sedimentary rock composed chiefly of calcium carbonate, commonly formed from biological debris or chemical precipitation. Calcite is the principal mineral in most limestone.
Carbonate sedimentation : Carbonate sedimentation is the accumulation of carbonate minerals and biological remains in sedimentary environments. It produces widespread deposits that later become calcite-rich limestone.
Aragonite : Aragonite is an orthorhombic crystalline form of calcium carbonate, distinct from calcite’s trigonal structure. The two minerals share composition but differ in crystal structure and stability.
Crystal system : A crystal system classifies crystals by the symmetry and geometry of their unit cells. Calcite’s trigonal symmetry determines its characteristic crystal forms.
Double refraction : Double refraction is the separation of a light ray into two refracted rays in certain crystals. Iceland spar makes calcite’s double refraction visible in ordinary objects beneath it.
Marble : Marble is a metamorphic rock formed when carbonate-rich rocks recrystallize under heat and pressure. Calcite commonly recrystallizes into the interlocking grains of marble.
Biomineralization : Biomineralization is the process by which organisms produce mineral structures such as shells, teeth, or skeletons. Many marine organisms build shells from calcite or other calcium carbonate forms.
Dolomite (mineral) : Dolomite is a carbonate mineral, CaMg(CO₃)₂, containing calcium and magnesium. Its magnesium content and weaker reaction to cold dilute acid help distinguish it from calcite.
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