mineral

Black tourmaline (schorl)

Schorl, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Hardness 7–7.5 Mohs; opaque black, commonly vitreous to resinous luster, trigonal crystals, and uneven fracture. The specimen appears to be a rough, broken/prismatic piece, though its exact identity cannot be confirmed from the image alone.

Identified September 4, 2026More mineral →

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Physical properties

Formation & geological history

Forms in boron-rich hydrothermal veins, pegmatites, and metamorphic rocks, crystallizing during late-stage cooling of granitic magmas or fluid alteration. Deposits range from Precambrian to recent geological ages.

Uses & applications

Used as a collector mineral and occasionally in jewelry; gem-quality tourmaline is faceted, while ordinary schorl has limited industrial value.

Geological facts

Schorl is the most common tourmaline species and can show strong pyroelectric and piezoelectric effects when heated or stressed.

Field identification & locations

Look for elongated, striated, triangular-to-rounded prismatic crystals and black color; similar dark obsidian lacks crystal striations, while ilmenite is usually heavier and metallic. Common localities include Brazil, Afghanistan, Madagascar, Namibia, and Maine, USA.