mineral

Black tourmaline

Schorl tourmaline, NaFe2+3Al6(BO3)3Si6O18(OH)4

AI-generated identification · may be incorrect

Black, vitreous to resinous luster; commonly prismatic with striations, though this piece appears tumbled or broken. Mohs hardness 7–7.5, brittle, trigonal crystal system, poor cleavage, specific gravity about 3.1–3.3.

Identified September 16, 2026More mineral →

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Physical properties

Formation & geological history

Forms in boron-rich hydrothermal veins, granite pegmatites, and metamorphic rocks, crystallizing mainly during late igneous activity or metamorphism. Specimen age depends on its deposit, commonly millions to billions of years.

Uses & applications

Used as a collector mineral, gemstone, and occasionally in jewelry; industrial tourmaline has limited use. Small common pieces typically have modest value.

Geological facts

Schorl is the most abundant tourmaline variety and owes its black color mainly to iron. Tourmaline is strongly piezoelectric and becomes electrically charged when heated or compressed.

Field identification & locations

Identify it by its deep black color, glassy luster, hardness, and longitudinal crystal striations; a polished piece may lack obvious crystal form. Common sources include Brazil, Afghanistan, Pakistan, Madagascar, and the United States.