4.2" Lustrous Calcite Crystal Cluster with Pyrite - Fluorescent!
This is a gorgeous cluster of lustrous calcite crystals that formed in association with sparkling pyrite crystals. It was collected from the El Hammam Mine in the Khémisset Province of Morocco. Under short-wave ultraviolet light, the calcite crystals exhibit orange fluorescence.
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.