This Specimen has been sold.
1" Quartz and Calcite Crystal Cluster Heart - Uruguay
This is a small, 1" wide quartz and calcite heart from the amethyst mines near Artigas, Uruguay. It was mined from within a pocket in the basalt. The quartz is actually colorless and it is the dark matrix beneath that gives it the appearance of the crystals having color. It has been cut into the shape of a heart and would make an excellent gift and/or jewelry piece.
Silicon Dioxide, also known as SiO2 or Quartz, is the second most abundant mineral in the Earth's crust. Quartz crystals generally grow in silica-rich, hot watery solutions called hydrothermal environments, at temperatures between 100°C and 450°C, and usually under very high pressure. Quartz veins are formed when open fissures are filled with hot water during the closing stages of mountains forming, and can be hundreds of millions of years old.
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.