mineral

Black Tourmaline

Schorl (Sodium Iron Aluminum Borosilicate Hydroxide)

Hardness: 7-7.5. Color: Deep black, opaque. Luster: Vitreous to sub-metallic. Crystal structure: Trigonal/Hexagonal with vertical striations. Cleavage: Indistinct. Specific gravity: 2.8-3.3.

Hardness: 7-7
Color: Deep black, opaque
Luster: Vitreous to sub-metallic

Identified April 11, 2026More mineral →

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Physical properties

Hardness: 7-7.5. Color: Deep black, opaque. Luster: Vitreous to sub-metallic. Crystal structure: Trigonal/Hexagonal with vertical striations. Cleavage: Indistinct. Specific gravity: 2.8-3.3.

Formation & geological history

Forms in igneous rocks like granite pegmatites or metamorphic rocks like schists. It is created through hydrothermal processes with boron-rich fluids. Found in formations millions of years old.

Uses & applications

Used in industry for its piezoelectric and pyroelectric properties (generating electricity under stress/heat), and widely used in mineral collections, metaphysical practices, and occasionally cabochon jewelry.

Geological facts

Black tourmaline is a 'pyroelectric' mineral, meaning it can become electrically charged when heated. Historically, it was called 'Aschentrekker' (ash puller) because it could attract fireplace ashes when warm.

Field identification & locations

Identify in the field by its distinct vertical ridges (striations) along the crystal length and its triangular/rounded-triangular cross-section. Common in Brazil, Madagascar, and the USA (California/Maine).

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