mineral

Black Tourmaline

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

AI-generated identification · may be incorrect

Hardness: 7-7.5 (Mohs); Color: Inky black; Luster: Vitreous to sub-metallic; Crystal structure: Trigonal/Hexagonal; Cleavage: Indistinct; Specific Gravity: 3.0-3.2

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

Identified March 25, 2026More mineral →

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Physical properties

Hardness: 7-7.5 (Mohs); Color: Inky black; Luster: Vitreous to sub-metallic; Crystal structure: Trigonal/Hexagonal; Cleavage: Indistinct; Specific Gravity: 3.0-3.2

Formation & geological history

Formed primarily in pegmatites through hydrothermal processes and in metamorphic rocks like schists during the late stages of magmatic cooling, often as accessory minerals.

Uses & applications

Used in high-pressure gauges (due to piezoelectric properties), minor industrial abrasive, metaphysical crystals, and semi-precious jewelry.

Geological facts

It is both pyroelectric (generates electricity when heated) and piezoelectric (generates electricity under pressure). Historically, Dutch traders called it 'Aschentrekker' because it could attract fireplace ashes when heated.

Field identification & locations

Identify by its characteristic vertical striations (if untumbled), triangular cross-section, and deep opaque black color. Commonly found in Brazil, Africa, and the USA (California and Maine). Collectors look for well-terminated unchipped crystals.