2.01" Smoky Quartz & Schorl, Erongo Mountains

Here is an excellent little cluster of smoky quartz crystals from the Erongo Mountains in Namibia. Although the crystal has broken away from the original hot rock or matrix it is in overall great shape, and there are a few tiny inclusions of schorl present.

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.

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.
Smoky Quartz, Schorl
Erongo Mountains, Namibia