1.95" Sparkling Druzy Quartz and Calcite on Basalt - India

Amethyst is a purple variety of quartz (SiO2) that owes its violet color to natural gamma irradiation, iron impurities, and the presence of trace elements, which result in complex crystal lattice substitutions. It is considered a semi-precious gemstone, and just two centuries ago was considered to have a value on par with diamonds, sapphires, and rubies. The largest and best known amethyst deposits occur in southern Brazil and Uruguay, where they are found in hydrothermally-formed geodes, but many localities around the world produce an amazing variety of amethyst crystals and formations. They are almost always formed in medium- to high-temperature geological settings.

Chabazite is the name for a series of minerals that include chabazite-Ca, chabazite-K, chabazite-Mg, chabazite-Na and chabazite-Sr. The variety of the crystal is dependent on the cation present during formation (Ca, K, Mg, Na or Sr). The red chabazite is commonly a calcium-dominant variety (chabazite-ca), the most prevalent of the chabazite series. Crystals usually exhibit a rhombohedral habit and can display a variety of colors including red, orange, yellow, and colorless.

Chavazite's general chemical formula is (Ca,K2,Na2)2[Al2Si4O12]2 · 12H2O.

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.