3.1" Hematite "Pagoda Calcite" Cluster (Fluorescent) - China
This is an inthralling cluster of "pagoda calcite" (also known as "mushroom calcite" and "poker chip calcite") crystals that are encrusted in hematite (iron oxidation). This specimen was collected from the Fengjiashan Mine (Daye Copper mine) in the Hubei Province of China. Under shortwave UV, the base of the crystals (portions not covered in hematite) fluoresce a vibrant orange 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.