mineral

Black tourmaline (probable schorl)

Schorl, sodium iron aluminum borosilicate hydroxide: NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Typically black, opaque, vitreous to resinous, with prismatic crystals and strong longitudinal striations; Mohs hardness 7–7.5, specific gravity about 3.1–3.3, and indistinct cleavage. The pictured rough, lustrous black specimen is consistent with massive or fractured schorl, though image-only identification is not def…

Identified September 16, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in boron-rich granitic pegmatites and hydrothermal veins during late igneous crystallization, commonly in Paleozoic to younger crust. It may occur with quartz, feldspar, mica, and other pegmatite minerals.

Uses & applications

Used as a collector mineral and occasionally as a gemstone; tourmaline’s piezoelectric and pyroelectric behavior has specialized technological applications. Black material is rarely used for high-value jewelry.

Geological facts

Tourmaline can develop electric charge when heated or compressed. Its characteristic striated prisms and black color make schorl the most readily recognized tourmaline variety.

Field identification & locations

Common in pegmatites worldwide, including Brazil, Afghanistan, Pakistan, Madagascar, Namibia, and the United States. Check for prismatic form, lengthwise grooves, hardness, and lack of magnetism; a loupe or testing is needed to distinguish it from obsidian or other black minerals.