3.25" Smoky Quartz - Erongo Mountains, Namibia

This is a beautiful schorl (black tourmaline) on smoky quartz from the Erongo Mountains, Namibia. Although there are some minor natural abrasions, the crystal is in overall great shape.

Tourmaline is a crystalline boron silicate mineral compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Schorl, or black tourmaline, is the most common form of tourmaline, and has been used for everything from jewelry to piezoelectric guitar pickups.

Silicon Dioxide, also know 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.

The color of smoky quartz results from free silicon, formed from the silicon dioxide by natural irradiation.