mineral
Black Tourmaline
Schorl (Sodium Iron Aluminum Borosilicate Hydroxide)
Hardness: 7-7.5 (Mohs), Color: Inky black, Luster: Vitreous to sub-metallic, Crystal Structure: Trigonal with vertical striations, Cleavage: Indistinct, Specific Gravity: 3.0-3.2
- Hardness
- 7-7
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Physical properties
Hardness: 7-7.5 (Mohs), Color: Inky black, Luster: Vitreous to sub-metallic, Crystal Structure: Trigonal with vertical striations, Cleavage: Indistinct, Specific Gravity: 3.0-3.2
Formation & geological history
Formed in granitic pegmatites and metamorphic rocks through hydrothermal processes involving boron-rich fluids. Often found in association with quartz and feldspar.
Uses & applications
Commonly used in jewelry (as beads or cabochons), metaphysical healing, and specifically in industry for its pyroelectric and piezoelectric properties for pressure gauges.
Geological facts
Black tourmaline is unique because it can become electrically charged when heated or squeezed (pyroelectricity and piezoelectricity). It is the most common variety of the tourmaline group.
Field identification & locations
Identify by its characteristic vertical striations along the length of the crystal and its triangular cross-section. Found globally with major deposits in Brazil, Africa, and the USA.
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