mineral

Black Tourmaline

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

Hardness: 7-7.5. 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 July 3, 2026More mineral →

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Physical properties

Hardness: 7-7.5. 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

Forms in igneous and metamorphic rocks, most notably in pegmatites where hydrothermal fluids rich in boron crystallize. Often found in granite and schist environments dating from the Precambrian to Cenozoic eras.

Uses & applications

Used primarily in metaphysical jewelry, geological collecting, and historically as a source of boron or in scientific instruments due to its piezoelectric and pyroelectric properties.

Geological facts

Black tourmaline is both piezoelectric (generates electric charge when mechanical stress is applied) and pyroelectric (generates charge when heated). It is the most common variety of tourmaline, making up 95% of all tourmaline in nature.

Field identification & locations

Identify by its deep black color, lack of transparency, and especially the long vertical ridges or striations on the prism faces. Common in Brazil, Madagascar, Africa, and the USA (California/Maine).