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 (often hexagonal prisms with vertical striations); Cleavage: Indistinct; Specific Gravity: 3.0-3.2

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

Identified June 12, 2026More mineral →

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Physical properties

Formation & geological history

Formed in granitic pegmatites, hydrothermal veins, and metamorphic rocks such as mica schists. These specimens can range from hundreds of millions to billions of years old depending on the host rock formation.

Uses & applications

Used in the gemstone industry for cabochons and beads, and increasingly popular in the metaphysical/collecting market. Historically used in scientific instruments due to its piezoelectric properties.

Geological facts

Black tourmaline is unique because it is pyroelectric (generates an electric charge when heated) and piezoelectric (generates a charge under pressure). It is the most common member of the tourmaline group.

Field identification & locations

Identify in the field by its characteristic vertical striations along the length of the crystal and its triangular cross-section. It is common in pegmatite districts globally, including Brazil, Namibia, and the USA (Maine, California).