mineral

Likely black tourmaline (schorl)

Schorl, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Black, vitreous-to-resinous luster with strong lengthwise striations and a prismatic crystal habit; Mohs hardness 7–7.5, specific gravity about 3.1–3.3, and poor cleavage. The specimen appears naturally terminated or broken, with pale quartz or feldspar attached/alongside it.

Identified August 19, 2026More mineral →

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Physical properties

Formation & geological history

Forms in boron-rich granitic pegmatites and hydrothermal veins as magma cools, commonly during the Precambrian through recent geologic time. Associated minerals include quartz, feldspar, mica, and other tourmalines.

Uses & applications

Used as a collector mineral, ornamental stone, and occasionally in jewelry; gem-quality schorl is uncommon because it is opaque. Tourmaline’s piezoelectric and pyroelectric properties have scientific and industrial applications.

Geological facts

Its longitudinal grooves are one of the best visual identifiers, and rubbing or heating can produce electric charge that attracts lightweight particles. Black tourmaline is the most common tourmaline variety.

Field identification & locations

Common localities include Brazil, Afghanistan, Pakistan, Madagascar, the United States, and pegmatites worldwide; verify with a streak test (usually white), hardness, and crystal striations. Avoid confusing it with black amphibole or hornblende, which are generally less sharply striated.