mineral

Black Tourmaline (Schorl)

Sodium Iron Aluminum Borate Silicate (NaFe3Al6(BO3)3Si6O18(OH)4)

Hardness: 7-7.5 on Mohs scale; Color: Jet black; Luster: Vitreous to sub-metallic; Crystal structure: Trigonal/Hexagonal columns with vertical striations; Cleavage: Indistinct; Specific Gravity: 3.0-3.2

Hardness: 7-7
Color: Jet black
Luster: Vitreous to sub-metallic

Identified March 7, 2026More mineral →

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Physical properties

Formation & geological history

Formed primarily in granitic pegmatites, hydrothermal veins, and occasionally in metamorphic rocks like schists during the cooling of boron-rich magma. Geological age varies globally from millions to billions of years depending on the host formation.

Uses & applications

Used widely in metaphysical jewelry and crystal collecting; industrially used for its pressure-sensitive electrical properties (piezoelectricity) in gauges, and in the production of hair styling tools to reduce static.

Geological facts

Tourmaline is pyroelectric, meaning it develops an electrical charge when heated. It also features 'pleochroism,' the ability to show different colors when viewed from different angles, though this is harder to see in the opaque black variety.

Field identification & locations

Identify in the field by looking for long, prismatic crystals with heavy vertical grooves (striations) on the faces and a triangular or six-sided rounded cross-section. Commonly found in Brazil, Namibia, and California, USA.

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