mineral

Black tourmaline in host rock

Schorl, NaFe3Al6(BO3)3Si6O18(OH)4, likely in quartz or feldspathic matrix

AI-generated identification · may be incorrect

Black, vitreous-to-resinous luster with elongated, fractured crystal surfaces; Mohs hardness 7–7.5, trigonal crystal structure, poor cleavage, and specific gravity about 3.0–3.3. The surrounding pale matrix appears quartz-rich or feldspathic.

Identified September 21, 2026More mineral →

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Physical properties

Formation & geological history

Forms in boron-rich hydrothermal fluids, commonly in granitic pegmatites and metamorphic rocks, usually during Precambrian to Phanerozoic geological events. Exact age and locality cannot be determined from the image.

Uses & applications

Used as a collector mineral, ornamental specimen, and occasionally in jewelry; gem-quality transparent tourmaline is valuable, while opaque matrix specimens are mainly decorative.

Geological facts

Schorl is the most common tourmaline species and can become electrically charged when heated or pressed (pyroelectric and piezoelectric).

Field identification & locations

Identify by its deep black color, elongated striated crystals, glassy luster, hardness, and lack of obvious cleavage; common localities include Brazil, Afghanistan, Pakistan, Namibia, Madagascar, and the United States.