-------------------------------------------------------------------------------- Chemical Formula: SiO2 Mineral Name: Quartz Color: Varies as per the spectrum Hardness: 7 Specific Gravity: 2.65 -------------------------------------------------------------------------------- Quartz is a very common mineral found in all types of geological environment. It clearly varies in terms of varieties, colors and forms. Some of the macrocrystalline or large crystal varieties are popular as ornamental stones and gemstones. » Amethyst, a purple gemstone » Citrine, a yellow to orange gemstone » Milky Quartz, a cloudy white gemstone » Rock crystal, a clear gemstone » Rose quartz, a pink to reddish pink gemstone » Smoky quartz, a brown to gray gemstone Cryptocrystalline (crystals too small to be seen even by a microscope) varieties are also used as semi-precious stones and for ornamental purposes. Chalcedony or agate is divided into innumeral types that have been named for locally common varieties. Some beautiful types of quartz include: » Chrysoprase (a pure green agate) » Sard (a yellow to brown agate) » Sardonyx (banded sard) » Onyx(black and white agate) » Carnelian (a yellow to orange agate) » Flint (a colorful and microscopically fibrous form) » Jasper (a colorful impure agate) » Bloodstone (a green with red speckled agate). Quartz has a unique structure that involves corkscrewing (helix) chains of silicon tetrahedrons and is a beautiful mineral to collect thus, serve as collectors' delight. Fine Quartz are known for their crystal habit, hardness, striations, good conchoidal fracture and lack of good cleavage. There are many variations of rutilated quartz that display built in other visible elements.These are often sought after by collectors . Major occurrences of amethyst are Australia, Brazil, Uraguay, Mexico, Russia, and Thunder Bay area of Canada, Brazil, South Africa, Mexico, Germany and some regions in the USA.