mineral

Black tourmaline (schorl)

Schorl, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Black, opaque, vitreous to resinous luster; commonly forms striated prismatic crystals with uneven fracture and no prominent cleavage. Mohs hardness 7–7.5; specific gravity about 3.0–3.3.

Identified September 11, 2026More mineral →

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Physical properties

Black, opaque, vitreous to resinous luster; commonly forms striated prismatic crystals with uneven fracture and no prominent cleavage. Mohs hardness 7–7.5; specific gravity about 3.0–3.3.

Formation & geological history

A boron-rich mineral formed mainly in granitic pegmatites, hydrothermal veins, and metamorphic rocks during late-stage crystallization; specimens range from Precambrian to recent geological settings.

Uses & applications

Used as a collector mineral and occasionally as a gemstone; tourmaline’s piezoelectric and pyroelectric properties support specialty scientific and electrical applications.

Geological facts

Schorl is the most abundant tourmaline species and is strongly pleochroic in transparent crystals. Heating or pressure can produce electrical charges at opposite crystal ends.

Field identification & locations

Identify by its jet-black color, lengthwise striations, hard glassy surface, and often triangular or rounded cross-section; common in Brazil, Afghanistan, Pakistan, Madagascar, Namibia, and the United States. The pictured fragment may also be a dark tourmaline-bearing rock, so confirmation requires testing.