mineral

Tumbled black tourmaline

Schorl, NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Black, opaque, vitreous to resinous luster; Mohs hardness 7–7.5, trigonal crystal structure, and indistinct cleavage. The visible narrow golden-brown line may be a natural inclusion, fracture, or surface reflection rather than diagnostic banding.

Identified August 25, 2026More mineral →

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Physical properties

Formation & geological history

Forms in boron-rich granitic pegmatites and hydrothermal veins during late-stage magma crystallization, commonly in Precambrian to younger continental crust. The specimen appears polished or tumbled.

Uses & applications

Used as an ornamental and metaphysical stone, cabochon material, and mineral-collection specimen; gem-quality schorl is uncommon and usually not highly valuable.

Geological facts

Tourmaline is strongly pleochroic and can become electrically polarized when heated or rubbed (the tourmaline effect). Schorl is the most common black tourmaline variety.

Field identification & locations

Identify by its very dark color, glassy luster, hardness, and typically striated prismatic crystals; confirm with streak, hardness, and specific gravity tests. Common sources include Brazil, Afghanistan, Madagascar, Namibia, and the United States.