mineral

Schorl (Black Tourmaline)

NaFe3Al6Si6O18(BO3)3(OH)3OH (Iron tourmaline)

Hardness: 7-7.5 (Mohs); Color: Black to deep brownish-black; Luster: Vitreous to sub-metallic; Crystal structure: Trigonal/Hexagonal columns; Cleavage: Indistinct; Specific Gravity: 3.0-3.2.

Hardness: 7-7
Color: Black to deep brownish-black
Luster: Vitreous to sub-metallic

Identified March 29, 2026More mineral →

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Physical properties

Hardness: 7-7.5 (Mohs); Color: Black to deep brownish-black; Luster: Vitreous to sub-metallic; Crystal structure: Trigonal/Hexagonal columns; Cleavage: Indistinct; Specific Gravity: 3.0-3.2.

Formation & geological history

Formed in granitic pegmatites, hydrothermal veins, and metamorphic rocks such as schists. It occurs when boron-rich fluids crystallize during the late stages of magma cooling.

Uses & applications

Commonly used as a decorative stone, in jewelry (beads/cabochons), and as a popular specimen for mineral collectors. In industry, it is sometimes used for its piezoelectric properties in pressure gauges.

Geological facts

Black tourmaline is pyroelectric, meaning it can generate an electrical charge when heated. It is the most common variety of tourmaline, making up about 95% of all tourmaline found in nature.

Field identification & locations

Identify in the field by its deep black color, lack of transparency, and long, striated (parallel-lined) prism faces. Common locations include Brazil, Namibia, Madagascar, and the United States (California/Maine).

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