2.58" Twinned Calcite Crystal on Dolomite Matrix - Missouri

This specimen contains a yellow, twinned calcite crystal that formed from a dolomite crystal encrusted matrix. This mineral cluster was collected from the Fletcher Mine in Reynolds County, Missouri. The longest calcite crystal is 2.58" 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.
Calcite & Dolomite
Fletcher Mine, West Fork, Reynolds County, Missouri
2.58" long calcite 3.1 x 2.2"