mineral

Black tourmaline

Schorl, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Mohs hardness 7–7.5; opaque black color, vitreous to resinous luster, trigonal crystal structure, and strong lengthwise striations. The elongated piece appears polished or naturally terminated, with no obvious cleavage.

Identified September 2, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in granitic pegmatites and hydrothermal veins when boron-rich fluids crystallize; specimens range from Precambrian to modern geological settings. Common sources include Brazil, Afghanistan, Pakistan, Namibia, Madagascar, and the United States.

Uses & applications

Used primarily as a collector mineral, ornamental stone, and occasionally in jewelry; tourmaline’s piezoelectric and pyroelectric properties support scientific and instrument applications. Black schorl is not generally used as a major construction material.

Geological facts

Its striated prismatic crystals and electrical response when heated or pressured are characteristic. Black tourmaline is often sold as a decorative or metaphysical stone, though claimed protective effects are not scientifically established.

Field identification & locations

Identify it by its dense black color, elongated prismatic form, longitudinal grooves, and hardness sufficient to scratch glass. Distinguish it from obsidian by the striations and from hornblende by its more strongly prismatic, often triangular cross-section.