mineral

Black Tourmaline (Schorl)

NaFe3+3Al6(BO3)3Si6O18(OH)4

Hardness: 7 to 7.5 on Mohs scale. Color: Opaque jet black, often with minor tan/brown matrix inclusions. Luster: Vitreous to sub-metallic. Crystal Structure: Trigonal, typically forming elongated, prismatic columnar crystals with vertical striations. Cleavage: Indistinct. Specific gravity: 3.0 to 3.2.

Hardness: 7 to 7
Luster: Vitreous to sub-metallic

Identified July 26, 2026More mineral →

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Physical properties

Formation & geological history

Formed in granitic pegmatites, hydrothermal veins, and metamorphic rocks enriched with boron during cooling magmatic fluids or deep metamorphism.

Uses & applications

Widely collected by mineral enthusiasts, used in metaphysical jewelry, cabochons, carved ornaments, and historically in scientific instruments for pressure sensors due to its piezoelectric properties.

Geological facts

Black Tourmaline (Schorl) accounts for nearly 95% of all tourmaline found in nature. It exhibits both pyroelectricity (electric charge generated by temperature change) and piezoelectricity (electric charge generated by mechanical stress).

Field identification & locations

Look for vertical striations along prismatic faces, triangular cross-section when viewed from the end, high hardness, and heavy black color. Commonly found in Brazil, Madagascar, Pakistan, Namibia, and Maine/California in the US.

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