mineral

Tumbled black tourmaline

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

AI-generated identification · may be incorrect

Black, opaque, glassy to resinous luster with elongated striations; Mohs hardness 7–7.5, trigonal crystal structure, and poor cleavage. The rounded shape indicates tumbling or polishing; internal brown streaks may reflect altered or iron-rich zones.

Identified September 4, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in boron-rich granite pegmatites and hydrothermal veins, commonly during late stages of igneous crystallization. Specimen age depends on its host rock, often hundreds of millions to over a billion years.

Uses & applications

Used as an ornamental stone, lapidary material, and collector specimen; gem-quality schorl is uncommon, while black tourmaline is widely sold for metaphysical purposes.

Geological facts

Tourmaline is strongly piezoelectric and becomes electrically charged when heated or compressed. Schorl is the most abundant tourmaline species.

Field identification & locations

Identify it by its deep black color, longitudinal striations, high hardness, and commonly prismatic form; common sources include Brazil, Afghanistan, Pakistan, Madagascar, and the United States.