mineral

Black tourmaline (likely schorl)

Schorl, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Opaque black, vitreous to resinous luster, commonly striated prismatic crystals; Mohs hardness 7–7.5, specific gravity about 3.1–3.3, with indistinct cleavage and conchoidal fracture. The image is too unclear for definitive identification; black obsidian or another dark mineral is possible.

Identified August 21, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in granitic pegmatites, hydrothermal veins, and metamorphic rocks during late-stage magmatic crystallization. Most specimens are geologically young relative to Earth history, ranging from Precambrian to recent deposits.

Uses & applications

Used as a collector mineral, ornamental stone, and occasionally in jewelry; industrial tourmaline applications are limited. Black specimens are usually valued for appearance rather than gem quality.

Geological facts

Tourmaline is strongly pleochroic and becomes electrically polarized when heated or compressed (pyroelectric and piezoelectric). Schorl is the most common tourmaline species.

Field identification & locations

Look for elongated, triangular-to-rounded striated crystals and a black streak or dark fracture surface; test hardness against glass cautiously. Common sources include Brazil, Afghanistan, Pakistan, Madagascar, and the United States.