mineral

Black tourmaline (schorl)

Schorl, a sodium–iron borosilicate: NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Typically black with a vitreous to submetallic luster and lengthwise striations; Mohs hardness 7–7.5, trigonal crystal system, and poor cleavage. The specimen appears to be a dark, elongated, possibly rough or broken crystal; exact identification from the image is uncertain.

Identified October 5, 2026More mineral →

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Physical properties

Formation & geological history

Commonly crystallizes in granitic pegmatites and metamorphic rocks as silica-rich magma cools; formation ages vary by deposit, often hundreds of millions to billions of years.

Uses & applications

Used as a gemstone and mineral specimen; tourmaline’s electrical properties also have specialized scientific and industrial applications.

Geological facts

Schorl is the most abundant tourmaline variety and can develop strongly striated prismatic crystals.

Field identification & locations

Look for a black, elongated prism with prominent parallel grooves and a roughly triangular cross-section; common sources include Brazil, Afghanistan, Pakistan, and the United States. The image lacks diagnostic crystal ends, so identification is provisional.