mineral

Black Tourmaline (Schorl)

Schorl (NaFe2+3Al6(Si6O18)(BO3)3(OH)3OH)

Hardness: 7-7.5 (Mohs scale), Color: Inky black to dark green, Luster: Vitreous to sub-metallic, Crystal Structure: Trigonal/Hexagonal with vertical striations, Cleavage: Indistinct, Specific Gravity: 3.0-3.25

Hardness: 7-7

Identified June 18, 2026More mineral →

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Physical properties

Formation & geological history

Primarily forms in igneous granitic pegmatites and metamorphic rocks like schists and marbles through hydrothermal processes involving boron-rich fluids. Can be found in deposits ranging from Precambrian to Cenozoic eras.

Uses & applications

Used in the manufacturing of pressure gauges due to piezoelectric properties, as gemstones in jewelry, and widely collected as a metaphysical or healing stone. It is also an important source of boron.

Geological facts

Tourmaline is both pyroelectric (develops electric charge when heated) and piezoelectric (develops charge under pressure). In the 1700s, Dutch traders used heated tourmaline crystals to pull ash out of their meerschaum pipes.

Field identification & locations

Identified by its triangular or rounded-triangular cross-section, deep vertical striations (parallel lines) along the length of the crystal, and extreme hardness. Commonly found in Brazil, Africa, and the USA (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

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

Green Apatite on Albite

Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]

mineral