Yellow-Green Apatite Crystals in Salmon Calcite - Canada

Apatite is the name given to a generic group of isomorphous hexagonal phosphate minerals. Its name comes from the Greek word apatite, which means 'to deceive': this is because apatite often resembles other common hexagonal-habit minerals. Their bright, lustrous crystals are often found in vugs (small cavities in rock) associated with quartz and calcite. Many crystals are around an inch in length, though larger crystals up to about 4 inches long have been found.

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.