mineral
Black Tourmaline (Schorl)
Schorl (NaFe3Al6(BO3)3Si6O18(OH)4)
AI-generated identification · may be incorrectHardness: 7-7.5 on Mohs scale; Color: Black to brownish-black; Luster: Vitreous to sub-vitreous; Crystal Structure: Trigonal (often hexagonal prisms in raw form); Cleavage: Indistinct; Specific Gravity: 3.0-3.2
- Hardness
- 7-7
- Color
- Black to brownish-black
- Luster
- Vitreous to sub-vitreous
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Physical properties
Hardness: 7-7.5 on Mohs scale; Color: Black to brownish-black; Luster: Vitreous to sub-vitreous; Crystal Structure: Trigonal (often hexagonal prisms in raw form); Cleavage: Indistinct; Specific Gravity: 3.0-3.2
Formation & geological history
Forms in igneous and metamorphic rocks, most notably in granitic pegmatites, hydrothermal veins, and schists. It is a complex silicate mineral containing boron.
Uses & applications
Primarily used for gemstone collecting, lapidary work, and spiritual/metaphysical jewelry. Some high-quality specimens are used in scientific instruments for their piezoelectric properties.
Geological facts
Black tourmaline is both pyroelectric (generates electricity when heated) and piezoelectric (generates electricity under pressure). It is the most common variety of the tourmaline group, making up 95% of all tourmaline in nature.
Field identification & locations
Identify in the field by its vertical striations along the length of the crystal, triangular cross-section, and intense black color. Found worldwide, with major deposits in Brazil, Namibia, and the USA (California and Maine).
