mineral

Black Tourmaline

Schorl (NaFe3Al6(BO3)3Si6O18(OH)4)

Hardness: 7-7.5 (Mohs scale), Color: Inky black, Luster: Vitreous to sub-metallic, Crystal Structure: Trigonal (often prismatic with vertical striations), Cleavage: Indistinct/Indiscernible, Specific Gravity: 3.0-3.2

Hardness: 7-7

Identified June 17, 2026More mineral →

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Physical properties

Formation & geological history

Commonly forms in granitic pegmatites, hydrothermal veins, and metamorphic rocks such as mica schists via boron-rich fluids during the late stages of magmatic crystallization.

Uses & applications

Widely used in jewelry when faceted, as a collector specimen, and in industry for its pyroelectric and piezoelectric properties (gauges for measuring pressure transients).

Geological facts

Black tourmaline is the most common variety of tourmaline, making up 95% of all tourmaline in nature. It is strongly pleochroic and can become electrically charged when heated or squeezed.

Field identification & locations

Identify in the field by its characteristic jet-black color, triangular or hexagonal cross-section, and prominent vertical grooves (striations) running down the long axis of the crystals. Found globally in Brazil, Namibia, and the USA (California and Maine).