mineral

Raw black tourmaline (likely schorl)

Schorl, sodium–iron tourmaline; approximately NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Usually black, vitreous to resinous, with elongated prismatic crystals and strong longitudinal striations; Mohs hardness 7–7.5, no distinct cleavage, and specific gravity about 3.0–3.3. The specimen appears to be a small, rough, reflective black crystal aggregate.

Identified August 11, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in granitic pegmatites and hydrothermal veins during late-stage crystallization of silica-rich magma, commonly in the Mesozoic to younger geological record. Exact age cannot be determined from the photograph.

Uses & applications

Used as a collector mineral, ornamental stone, and occasionally in jewelry; gem-quality transparent tourmaline varieties are more valuable than opaque schorl. Tourmaline is also valued for its piezoelectric and pyroelectric properties.

Geological facts

Tourmaline crystals can become electrically charged when heated or pressed. Schorl is the most common tourmaline species and commonly occurs with quartz, feldspar, and mica.

Field identification & locations

Look for black, striated prismatic crystals that may attract dust when rubbed or heated; confirm with hardness and crystal form, since slag and obsidian can look similar. Common localities include Brazil, Afghanistan, Pakistan, Madagascar, Namibia, and the United States.