mineral

Schorl (Black Tourmaline)

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

Hardness: 7-7.5 on Mohs scale; Color: Jet black to brownish black; Luster: Vitreous to resinous; Crystal structure: Trigonal/Hexagonal with vertical striations; Cleavage: Indistinct; Specific gravity: 3.0-3.2

Hardness: 7-7
Color: Jet black to brownish black
Luster: Vitreous to resinous

Identified January 1, 2026More mineral →

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Physical properties

Formation & geological history

Formed in granitic pegmatites, hydrothermal veins, and metamorphic rocks such as mica schists. It is formed through Boron-rich fluids cooling at high temperatures in deep crustal environments.

Uses & applications

Used primarily as a gemstone in jewelry, an ornamental collector's mineral, and in scientific instruments for its pyroelectric and piezoelectric properties.

Geological facts

Black tourmaline is unique because it becomes electrically charged when heated (pyroelectricity) or squeezed (piezoelectricity). It is the most common member of the tourmaline group.

Field identification & locations

Identify in the field by its characteristic long, prismatic crystal shape with deep vertical grooves (striations) on the faces and a lack of visible cleavage. Commonly found in Brazil, Namibia, and the United States (California, Maine).

Other mineral specimens

See all

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Schist

Metamorphic

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

metamorphic

Gypsum (variety Selenite or Alabaster)

Calcium sulfate dihydrate (CaSO4·2H2O)

Mineral

Nephrite Jade

Nephrite

Mineral/Rock

Granite

Granite (Phaneritic intrusive igneous rock)

igneous