mineral

Black tourmaline

Schorl tourmaline — NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Typically black, with a vitreous-to-resinous luster, strong longitudinal striations, and an elongated trigonal crystal form; Mohs hardness 7–7.5, specific gravity about 3.0–3.3, and indistinct cleavage. The pictured rough, striated fragment is consistent with schorl, though a photo cannot confirm identity.

Identified August 20, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in granitic pegmatites and metamorphic rocks from boron-rich hydrothermal fluids, commonly during late stages of granite crystallization. Tourmaline occurs from Precambrian to recent geological settings.

Uses & applications

Used as a collector mineral, ornamental stone, and occasionally in jewelry; fine crystals can be cut or polished, while tourmaline’s piezoelectric properties support scientific and electrical applications.

Geological facts

Tourmaline becomes electrically polarized when heated or pressured (the pyroelectric and piezoelectric effects). Black schorl is the most abundant tourmaline variety.

Field identification & locations

Look for a black prismatic crystal with parallel grooves, triangular or rounded cross-section, and hardness sufficient to scratch glass; test carefully because coatings and similar minerals can mislead. Common localities include Brazil, Afghanistan, Pakistan, Madagascar, Namibia, and the United States.