Chemistry: Quartz

Amethyst a variety of quarts.

Quarts is one of the most common minerals on earth. Quarts is Silicon dioxide (SiO2) . Quarts comes in a variety of colors but pure quartz is colorless or white. Quarts forms hexagonal prisms top with a pyramid. Quartz has a hardness of 7 on the Mohs scale and a density of 2.65 g/cm³.

The name "quartz" comes from the German "Quarz", which is of Slavic origin (Czech miners called it křemen). Other sources insist the name is from the Saxon word "Querkluftertz", meaning cross-vein ore.Quartz is important as a rock forming mineral and a semi-precious stone. Quarts makes up much of the dust in the air. Quarts leaves a white streak and has a specific gravity of 2.65 when pure. Quartz crystals can grow to huge sizes in pegmatites. a single crystal of approximately 40 tons was found in Brazil and one of 70 t0ns was found in Kazakstan.

Sources:
Wikimedia.
Wikipededia
Rocks and Fossils by Arther B. Busbey III, Robert R. Coenraads, David Roots and Paul Willis. (book)