13" Green-Black Calcite Crystal Cluster - Sweetwater Mine

This is a stunning, green-black calcite crystal cluster that was collected in 2019 from the Sweetwater Mine of Reynolds County, Missouri. The calcite crystals are in scalenohedral form and have several layers of chalcopyrite inclusions throughout. A large section of chalcopyrite crystal encrusted matrix is still attached to this specimen.

There is one crystal along the edge of the specimen that has a cleaved off termination. The rest of the calcite on this specimen is in excellent condition with very little to no damage. It sits nicely on a flat surface without the need for a display stand.

These green-black calcite aggregations (also known as "black calcite" and "dragon scale calcite") come from the Sweetwater Mine in Reynolds County, Missouri. They're collected at about 1,400 ft elevation, from stope J-21 (copper side). Their green-black coloration can be attributed to chalcopyrite inclusions that are suspended in layers throughout the crystals, resulting in fascinating phantoms. Both microscopic and larger chalcopyrite crystals can be found beneath the exterior-most layers of calcite.

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 as well, 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 & Chalcopyrite
Sweetwater Mine, Reynolds County, Missouri
13 x 8.2 x 7.7"