1.4" Garnet Cluster with Calcite & Feldspar - Pakistan
This garnet centered specimen comes from a location in Pakistan, where associations of deep orange/brown garnets, feldspar, golden mica, green epidote, and calcite are typically found. The garnets from this location display a unique pattern, which can be seen along the faces of the crystals when rotated under light.
Garnets are nesosilicates having the general formula X3Y2(SiO4)3. There are many species of garnet which include pyrope, almandine, spessartine, uvarovite, andradite and grossular (varieties of which are hessonite, cinnamon-stone and tsavorite). Garnets are found in a wide variety of colors including red, orange, yellow, green, purple, brown, blue, black, pink, and colorless, with reddish shades being the most common.
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.