1.9" Intense Orange Calcite Crystal Cluster - Poland
This is a cluster of sharp orange calcite crystals on basalt. This comes from the Grabiszyce Basalt Quarry in the Luban District of Poland. Under short and long wave UV, these crystals fluoresce a white-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.