mineral

Black Tourmaline

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

Hardness: 7-7.5 on Mohs scale; Color: Jet black; Luster: Vitreous to sub-metallic; Crystal structure: Trigonal/Hexagonal with vertical striations; Cleavage: Indistinct; Specific Gravity: 3.0-3.2

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

Identified March 9, 2026More mineral →

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Physical properties

Hardness: 7-7.5 on Mohs scale; Color: Jet black; Luster: Vitreous to sub-metallic; Crystal structure: Trigonal/Hexagonal with vertical striations; Cleavage: Indistinct; Specific Gravity: 3.0-3.2

Formation & geological history

Formed primarily in granitic pegmatites and metamorphic rocks through hydrothermal processes where boron and iron are present. Occurs in deposits spanning various geological ages from the Precambrian to more recent eras.

Uses & applications

Used in jewelry (cabochons and beads), as an industrial pressure sensor (due to piezoelectric properties), for scientific instrumentation, and widely sold as a 'protection stone' in metaphysical and collector markets.

Geological facts

Black tourmaline is both piezoelectric (generates electricity under pressure) and pyroelectric (generates electricity when heated), which allows it to attract dust and light particles. It is the most common member of the tourmaline group, making up 95% of all tourmaline in nature.

Field identification & locations

Identify in the field by its distinct long, columnar crystals with vertical ridges (striations) and its triangular or six-sided cross-section. Commonly found in Brazil, Namibia, the United States (Maine/California), and Pakistan. It is opaque and does not transmit light even on thin edges.