3.4" Calcite Crystal Clusters in Dolomite Matrix - Missouri

This specimen contains clusters of light yellow colored calcite crystals of various sizes, all scattered within a dolomite matrix. The longest calcite crystal is 1.3" long.

Calcite, CaCO3, is a carbonate mineral and the most stable polymorph of calcium carbonate. The other polymorphs are the minerals aragonite and vaterite. Calcite crystals are trigonal-rhombohedral, though actual calcite rhombohedra are rare as natural crystals. However, they show a remarkable variety of habits including acute to obtuse rhombohedra, tabular forms, and prisms. Calcite exhibits several twinning types adding to the variety of observed forms. It may occur as fibrous, granular, lamellar, or compact. Cleavage is usually in three directions parallel to the rhombohedron form. Its fracture is conchoidal, but difficult to obtain.
Reynolds County, Missouri
3.4" long, 2.7" wide