mineral

Black Tourmaline

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

Hardness: 7 to 7.5; Color: Jet black; Luster: Vitreous to sub-metallic; Crystal structure: Trigonal/Hexagonal with vertical striations; Cleavage: Poor/indistinct; Specific gravity: 3.0 to 3.25.

Hardness: 7 to 7
Color: Jet black
Luster: Vitreous to sub-metallic

Identified May 26, 2026More mineral →

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Physical properties

Hardness: 7 to 7.5; Color: Jet black; Luster: Vitreous to sub-metallic; Crystal structure: Trigonal/Hexagonal with vertical striations; Cleavage: Poor/indistinct; Specific gravity: 3.0 to 3.25.

Formation & geological history

Formed primarily in granite pegmatites and certain metamorphic rocks like schist through hydrothermal activity involving boron-rich fluids.

Uses & applications

Used in gemstone collection, industrial pressure gauges (due to piezoelectricity), and popular in metaphysical and jewelry applications.

Geological facts

Tourmalines exhibit both piezoelectricity and pyroelectricity, meaning they generate an electrical charge when compressed or heated. Schorl comprises about 95% of all tourmaline found on Earth.

Field identification & locations

Identify by its characteristic heavy vertical striations (grooves) on the crystal face and its typically triangular rounded cross-section. Common in Brazil, Namibia, and the United States (Maine/California).