mineral

Black Tourmaline

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

Hardness: 7-7.5 (Mohs scale), Color: Inky black, Luster: Vitreous to sub-metallic, Crystal Structure: Trigonal (striated elongated prisms), Cleavage: Indistinct, Specific Gravity: 3.0-3.2

Hardness: 7-7

Identified May 24, 2026More mineral →

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Physical properties

Hardness: 7-7.5 (Mohs scale), Color: Inky black, Luster: Vitreous to sub-metallic, Crystal Structure: Trigonal (striated elongated prisms), Cleavage: Indistinct, Specific Gravity: 3.0-3.2

Formation & geological history

Formed in granitic pegmatites and metamorphic rocks through hydrothermal processes involving boron-rich fluids. Can be found in rocks from Precambrian to relatively recent Cenozoic ages.

Uses & applications

Primarily used as a minor gemstone, in metaphysical jewelry, and historically in scientific instruments like pressure gauges due to its piezoelectric properties.

Geological facts

Tourmaline is both pyroelectric (develops electric charge when heated) and piezoelectric (develops charge under pressure). Dutch traders called it 'Aschentrekker' because it would attract ash to its surface.

Field identification & locations

Identify by its characteristic vertical striations along the length of the crystal and its often triangular cross-section. Commonly found in Brazil, Madagascar, and Namibia.