mineral

Likely polished black tourmaline (schorl)

Schorl, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Opaque black to dark brown, vitreous-to-resinous luster, Mohs hardness 7–7.5, typically trigonal (usually prismatic) crystal structure with poor cleavage and strongly uneven fracture; specific gravity about 3.1–3.3. The faceted elongated shape and surface wear indicate a cut or polished specimen.

Identified September 12, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in granite pegmatites, hydrothermal veins, and metamorphic rocks when boron-rich fluids crystallize; individual crystals commonly formed during late Paleozoic–Mesozoic pegmatitic events, though age depends on locality.

Uses & applications

Used as a collector mineral, ornamental stone, and occasionally in jewelry; black tourmaline is also marketed for decorative and metaphysical purposes.

Geological facts

Schorl is the most common tourmaline variety and commonly shows strong longitudinal striations on natural crystal faces. The pictured piece could also be another dark stone, such as obsidian or basalt, because its crystal features are obscured by shaping.

Field identification & locations

Commonly found in Brazil, Afghanistan, Madagascar, Namibia, the United States, and Europe. Confirm by testing for tourmaline striations, hardness, and density; a gemological test is needed for certainty.