mineral

Schorl (Black Tourmaline)

NaFe3Al6(BO3)3Si6O18(OH)4 (Sodium Iron Aluminum Borosilicate)

Hardness: 7-7.5. Color: Jet black. Luster: Vitreous to sub-metallic. Crystal Structure: Trigonal/Hexagonal columns with vertical striations. Cleavage: Poor. Specific Gravity: 2.8-3.3.

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

Identified May 20, 2026More mineral →

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Physical properties

Hardness: 7-7.5. Color: Jet black. Luster: Vitreous to sub-metallic. Crystal Structure: Trigonal/Hexagonal columns with vertical striations. Cleavage: Poor. Specific Gravity: 2.8-3.3.

Formation & geological history

Formed in igneous pegmatites, hydrothermal veins, and metamorphic rocks such as schists. It crystalline directly from silicate liquids or hot fluids rich in boron.

Uses & applications

Used primarily as low-cost jewelry, cabinet specimens for collectors, and in metaphysical circles for 'grounding'. Historically used in pressure gauges due to piezoelectric properties.

Geological facts

Black tourmaline is the most common variety of tourmaline, 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 black color, intense vertical striations on crystal faces, and triangular or rounded-triangular cross-section. Commonly found in Brazil, Namibia, and the USA (California and Maine).

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