Quartz
Mohs Hardness - 7 Found in - Worldwide, but the best crystals are from Brazil. In the USA, locations include Arkansas & Herkimer NY. History - Crystal Quartz is a common mineral that can occur in a wide variety of colors, it's name is derived from the Slavic word kwardy (hard). It has valuable electrical and optical properties and is used in radios, watches, microscopes, etc. Quartz and Tourmaline are the only common gems known to be pzieoelectric (capable of producing opposite electrical charges when pressure is exerted upon both ends of a crystal. Quartz has been used since prehistoric times, and now finds uses as lenses, and in the manufacture of glass and porcelain, and abrasives. Metaphysical - Quartz is believed to have healing powers. The Greeks called quartz the "ice of eternity" because they thought the Gods formed the crystal by an irreversible freezing process. They learned that the sun's rays could be used to ignite things when focused through a rock crystal. Priests were given sole charge of this sacred fire and the idea that "petrified" water could create fire remained a great mystery in ancient times & gave many magical attributes to rock crystal. It was the favorite of soothsayers, hence the crystal ball. It was also through perfecting a technique of melting quartz that the Egyptians invented glass, almost 5000 years ago. Today it is thought to be a psychic amplifier, capable of divine and clairvoyant inspiration. Also considered to be an all around healer, to break bad habits, restore physical energy, protect against infection and injury, for headaches, and insomnia.