mineral

Likely black tourmaline (schorl) crystal

Schorl, a black iron-rich tourmaline; approximate formula NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Opaque black to dark brown, vitreous-to-submetallic luster, commonly elongated and striated with a triangular or prismatic cross-section; Mohs hardness 7–7.5, no true cleavage, specific gravity about 3.0–3.3. The image is somewhat blurry, so identification is provisional.

Identified August 14, 2026More mineral →

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Physical properties

Formation & geological history

Forms in boron-rich granitic pegmatites and hydrothermal veins as magma cools, typically in Precambrian to Phanerozoic rocks. Individual crystals may be millions to billions of years old.

Uses & applications

Used as a collector mineral and occasionally as a gemstone; tourmaline is also valued for its piezoelectric and pyroelectric properties, though common schorl has limited commercial value.

Geological facts

Black tourmaline can become electrically charged when heated or compressed. Its strong longitudinal striations and prismatic habit are especially diagnostic.

Field identification & locations

Look for a lustrous black, vertically striated crystal with a three-sided or six-sided prism and uneven fracture; common localities include Brazil, Afghanistan, Pakistan, Madagascar, Namibia, and the United States. Confirm with hardness and specific-gravity tests.