mineral

Black Tourmaline

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

Hardness: 7-7.5 on Mohs scale; Color: Deep black, opaque; Luster: Vitreous to sub-metallic; Crystal structure: Trigonal/Hexagonal with vertical striations (ridges); Cleavage: Poor/indistinct; Specific Gravity: 3.0-3.2

Hardness: 7-7
Color: Deep black, opaque
Luster: Vitreous to sub-metallic

Identified June 30, 2026More mineral →

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Physical properties

Formation & geological history

Formed primarily in pegmatites through hydrothermal processes where boron-rich fluids crystallize. Often found in granite and some metamorphic rocks like mica schists.

Uses & applications

Predominantly used for ornamental purposes, metaphysical collecting, and historically in scientific instruments (owing to its pyroelectric and piezoelectric properties).

Geological facts

Black tourmaline is unique because it can become electrically charged when heated (pyroelectricity) or when mechanical pressure is applied (piezoelectricity). It is the most common member of the tourmaline group.

Field identification & locations

Identify by its deep black color, vertical striations along the length of the crystal, and hard, brittle nature. It is commonly found in Brazil, Africa, and the United States (Maine/California).