mineral

Black tourmaline (schorl), possibly rough

Schorl tourmaline, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Typically black to very dark gray with a vitreous to resinous luster; Mohs hardness 7–7.5, trigonal crystal structure, indistinct cleavage, and specific gravity about 3.0–3.3. The specimen appears massive or irregularly fractured, with possible reflective crystal faces.

Identified September 2, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in granite pegmatites, hydrothermal veins, and metamorphic rocks during late-stage igneous or metamorphic activity. Individual crystals may form over millions of years; the specimen’s exact age and locality cannot be determined from the image.

Uses & applications

Used as a collector mineral, ornamental stone, and occasionally as a black gemstone; tourmaline’s piezoelectric and pyroelectric properties have technological applications. Common rough pieces generally have modest value.

Geological facts

Schorl is the most common tourmaline species and is strongly pleochroic under suitable observation. Heating or pressure can produce electrical charges at opposite crystal ends.

Field identification & locations

Look for elongated prismatic crystals with longitudinal striations, triangular cross-sections, and strong black color; hardness testing and locality information would help confirm it. Common sources include Brazil, Afghanistan, Pakistan, Namibia, Madagascar, and the United States.