mineral

Likely raw black tourmaline

Schorl tourmaline, NaFe3Al6(BO3)3Si6O18(OH)4

AI-generated identification · may be incorrect

Black, vitreous to resinous luster with a rough, possibly prismatic surface; Mohs hardness 7–7.5, no obvious cleavage, and strong characteristic elongate crystal structure. The image is insufficient to confirm composition; black amphibole or biotite are alternatives.

Identified September 8, 2026More mineral →

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Physical properties

Formation & geological history

Usually forms in lithium-rich granitic pegmatites and hydrothermal veins during late igneous crystallization, commonly in Precambrian to younger rocks. It occurs worldwide, notably in Brazil, Afghanistan, Pakistan, Madagascar, and the United States.

Uses & applications

Used as a collector mineral and occasionally as a gemstone; tourmaline’s piezoelectric and pyroelectric properties have specialized technical applications. Small rough pieces have little industrial value.

Geological facts

Schorl is the most common tourmaline species and commonly forms striated, three-sided or six-sided prisms. Heating or pressure can produce electrical charge at its ends.

Field identification & locations

Look for a black, elongated, vertically striated crystal and test hardness against glass; a magnet response may occur weakly from iron. Common localities include pegmatites in Maine, California, Brazil, and Namibia.