4.3" Pagoda Calcite Crystals on Calcite - Fluorescent!
This is a beautiful cluster of hematite included, "pagoda style" calcite crystals that formed after a large, hematite encrusted dogtooth (scalenohedral) calcite crystal. This specimen was collected from the Fengjiashan Mine in Hubei, China. Under short-wave ultraviolet, the colorless portions of the calcite react by fluorescing orange in color.
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.