13.5" Green-Black Calcite Crystal Cluster - Sweetwater Mine

This is a wonderful, 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. Additional chalcopyrite crystals can also be found along the "base" of the crystals where matrix is exposed.

The largest calcite crystal on this specimen is in pristine condition and measures just over 7.5" long and 4.2" wide! Some of the smaller crystals have damaged terminations.

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
13.5 x 5.4 x 5.2"