Black Tourmaline (Schorl)

Hardness: 7-7.5 on Mohs scale. Color: Opaque black. Luster: Vitreous to resinous. Crystal structure: Trigonal (often forms elongated, prismatic crystals with vertical striations). Cleavage: Indistinct. Specific gravity: 3.06-3.26.

Forms in igneous and metamorphic rocks (granites, pegmatites, schists, gneisses, and hydrothermal veins). It crystallizes from hot, boron-rich fluids. Geological age varies widely depending on the specific deposit, ranging from hundreds of millions to billions of years old.

Black Tourmaline is popular as a gemstone, especially in jewelry like the pictured pendant, due to its dark color and durability. It is also used in pressure gauges and other electrical devices due to its piezoelectric properties (generates an electric charge when subjected to mechanical stress) and pyroelectric properties (generates an electric charge when heated or cooled). In metaphysical practices, it's often used for protection and grounding.

Black Tourmaline, or Schorl, is the most common variety of Tourmaline, accounting for over 95% of all natural tourmaline. The name 'tourmaline' comes from the Sinhalese word 'turmali', meaning 'mixed colored stones', although Schorl itself is uniformly black. It is also known as a 'protective stone' in many cultures.

In the field, Black Tourmaline is identifiable by its characteristic black color, vitreous luster when broken, and typically long, prismatic crystals with strong vertical striations on its crystal faces. Its relative hardness (scratches glass) is also a good indicator. It's commonly found worldwide in areas rich in granite pegmatites and metamorphic rocks, with significant deposits in Brazil, Africa (e.g., Namibia, Tanzania), Pakistan, and the United States (e.g., Maine, California).