mineral

Black tourmaline (schorl)

Schorl, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Typically black, opaque, and glassy to resinous, with prismatic striations, poor cleavage, and conchoidal or uneven fracture; Mohs hardness 7–7.5, specific gravity about 3.0–3.3. The specimen appears cut or naturally terminated, with reflective fracture surfaces.

Identified September 8, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in boron-rich granitic pegmatites and hydrothermal veins during late-stage crystallization, commonly in Precambrian to Phanerozoic terrains. It is associated with quartz, feldspar, mica, and other pegmatite minerals.

Uses & applications

Used as a collector mineral, ornamental stone, and occasional gemstone; fine transparent tourmalines are faceted for jewelry, while black schorl is commonly sold as rough specimens or carvings.

Geological facts

Tourmaline is strongly piezoelectric and thermoelectric: heating or pressure can produce electrical polarization. Black schorl is the most abundant tourmaline variety.

Field identification & locations

Identify it by its deep black color, elongated prismatic form, lengthwise striations, high hardness, and lack of obvious cleavage; common localities include Brazil, Afghanistan, Madagascar, Namibia, and the United States.