mineral

Polished black tourmaline

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

AI-generated identification · may be incorrect

Hardness 7–7.5 Mohs; opaque black, vitreous to resinous luster, commonly strongly pleochroic, with trigonal crystals and prismatic/columnar structure. This appears to be a polished or tumbled piece, so cleavage and crystal striations are obscured.

Identified August 25, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in granitic pegmatites and hydrothermal veins during late-stage igneous crystallization, commonly in Paleozoic to younger continental crust. Iron-rich schorl is the most widespread black variety.

Uses & applications

Used as a durable ornamental stone, cabochon, carving material, and mineral specimen; occasionally used in jewelry and metaphysical collections.

Geological facts

Tourmaline is strongly piezoelectric and pyroelectric: it can develop electrical charge when compressed or heated. Black schorl is the most common tourmaline species.

Field identification & locations

Identify by its uniform black color, high polish, hardness, and—on rough material—long striated prismatic crystals; it is nonmagnetic or only weakly magnetic. Common sources include Brazil, Afghanistan, Pakistan, Madagascar, and the United States, especially Maine and California.