mineral
Black Tourmaline (Schorl)
Schorl (NaFe3Al6(BO3)3Si6O18(OH)4)
Hardness: 7-7.5. Color: Jet black to brownish black. Luster: Vitreous to sub-metallic. Crystal Structure: Trigonal (often hexagonal prisms with vertical striations). Specific Gravity: 3.1-3.3. Cleavage: Indistinct.
- Hardness
- 7-7
- Color
- Jet black to brownish black
- Luster
- Vitreous to sub-metallic
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Physical properties
Hardness: 7-7.5. Color: Jet black to brownish black. Luster: Vitreous to sub-metallic. Crystal Structure: Trigonal (often hexagonal prisms with vertical striations). Specific Gravity: 3.1-3.3. Cleavage: Indistinct.
Formation & geological history
Typically found in granitic pegmatites, hydrothermal veins, and metamorphic rocks such as schists. Formed under high pressure and temperature during late-stage crystallization of magma.
Uses & applications
Used as an industrial pyroelectric material, in pressure gauges, and widely used in jewelry (beads, cabochons) and as a protective stone in metaphysical collections.
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 generates an electrical charge when heated.
Field identification & locations
Identify by its deep black color, vertical striations on crystal faces, and a triangular or rounded triangular cross-section. Commonly found in Brazil, Namibia, and the USA (California/Maine).
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Mineral/Rock
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