mineral
Black Tourmaline (Schorl) on Quartz
NaFe2+3Al6(Si6O18)(BO3)3(OH)3(OH)
Hardness: 7-7.5 (Mohs scale), Color: Inky black, Luster: Vitreous to resinous, Crystal Structure: Trigonal, Cleavage: Indistinct, Specific Gravity: 3.0-3.2
- Hardness
- 7-7
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Physical properties
Hardness: 7-7.5 (Mohs scale), Color: Inky black, Luster: Vitreous to resinous, Crystal Structure: Trigonal, Cleavage: Indistinct, Specific Gravity: 3.0-3.2
Formation & geological history
Formed in igneous pegmatites or metamorphic rocks through hydrothermal processes where boron-rich fluids are present. Often found associated with quartz, feldspar, and mica.
Uses & applications
Primarily used for mineral specimen collecting, metaphysical jewelry, and industrial applications such as pressure gauges due to its piezoelectric properties.
Geological facts
Schorl is the most common member of the tourmaline group, making up 95% of all tourmaline in nature. It is strongly pyroelectric, meaning it develops an electrical charge when heated.
Field identification & locations
Identify by its characteristic trigonal cross-section (often rounded triangular), vertical striations on crystal faces, and intense black color. Found worldwide, with major deposits in Brazil and Namibia.
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