1.8" Black Tourmaline (Schorl) Crystals on Feldspar - Namibia

These are nice black tourmaline (schorl) crystals on a feldspar matrix, from the Erongo Mountains in Namibia.

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.