mineral

Black tourmaline

Schorl, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Typically black with vitreous to resinous luster, strong lengthwise striations, and prismatic crystals; Mohs hardness 7–7.5, specific gravity about 3.1–3.3. It has imperfect cleavage and a trigonal crystal structure; the pictured specimen appears rough and naturally fractured.

Identified September 6, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in boron-rich granitic pegmatites and hydrothermal veins during late-stage magma crystallization, commonly in Precambrian to younger continental rocks. Associated minerals include quartz, feldspar, mica, and albite.

Uses & applications

Used as a collector mineral, ornamental stone, and occasionally in jewelry; tourmaline’s piezoelectric and pyroelectric properties have specialized technical applications.

Geological facts

Schorl is the most common tourmaline species and is often mistaken for obsidian or coal. Heating or pressure can produce electrical charge at its ends.

Field identification & locations

Identify it by its opaque black color, elongated striated prisms, wedge-like terminations, and high hardness; it commonly occurs in Brazil, Afghanistan, Pakistan, Madagascar, Namibia, and the United States. A simple glass-scratch test can help distinguish it from softer look-alikes.