mineral

Black tourmaline (schorl)

Schorl, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Typically black, vitreous to resinous, with prismatic striated crystals and uneven fracture; Mohs hardness 7–7.5, specific gravity about 3.1–3.3. The specimen appears to be a rough, partly crystalline aggregate, though the image alone cannot exclude black mica or another dark mineral.

Identified September 16, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in boron-rich granitic pegmatites, hydrothermal veins, and metamorphic rocks during late-stage crystallization; commonly associated with quartz and feldspar. Individual crystals may be geologically young or hundreds of millions of years old, depending on the host formation.

Uses & applications

Used as a durable collector mineral, ornamental stone, and occasionally in jewelry; industrial applications include tourmaline-based electrical and pressure-sensitive devices.

Geological facts

Tourmaline is strongly pleochroic and can become electrically polarized when heated or compressed (pyroelectric and piezoelectric). Schorl is the most common tourmaline species.

Field identification & locations

Identify by black color, elongated striated prisms, high hardness, and possible electrical charge after heating; common localities include Brazil, Afghanistan, Pakistan, Madagascar, Namibia, and the United States. A strong glassy luster and flaky cleavage would instead suggest biotite mica.