mineral

Black tourmaline (likely schorl)

Schorl, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Black, opaque, vitreous-to-resinous luster; Mohs hardness 7–7.5; commonly forms trigonal prismatic crystals with strong longitudinal striations and indistinct cleavage. The fragment appears crystalline and highly reflective, though its tiny size limits certainty.

Identified September 8, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in granite-related pegmatites, hydrothermal veins, and metamorphic rocks, crystallizing from boron-rich fluids during late-stage magmatic or metamorphic activity. Tourmaline ranges from Precambrian to recent geological ages.

Uses & applications

Used as a gemstone, mineral specimen, and ornamental material; black schorl is also collected for its electrical piezoelectric and pyroelectric properties, though it has limited industrial use.

Geological facts

Tourmaline can become electrically polarized when heated or compressed, attracting dust and small particles. Color zoning is common, and schorl is the most abundant tourmaline species.

Field identification & locations

Look for a black, glassy prismatic crystal with lengthwise grooves, uneven fracture, and no obvious flat cleavage surfaces; it may show weak magnetic response if iron-rich. Common localities include Brazil, Afghanistan, Pakistan, Madagascar, and U.S. pegmatites in Maine and California.