3.6" Native Silver Formation in Calcite - Morocco
This is a 3.6" wide specimen of native silver in calcite. It was mined from the Bouismas Mine in the Zagora Province of Morocco. The silver has been acid etched free of the calcite which was originally surrounding it, revealing the beautiful plant-like branching structure.
Native silver (Ag) is an uncombined form of silver which occurs as a natural mineral. Silver is one of the few precious metallic elements to occur in native form, although it most commonly occurs naturally mixed with other elements like gold, mercury, arsenic and antimony.
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.