mineral

Schorl (Black Tourmaline)

NaFe3Al6(BO3)3Si6O18(OH)4 (Complex Borosilicate)

Hardness: 7-7.5 on Mohs scale. Color: Deep black, opaque. Luster: Vitreous to sub-metallic. Crystal structure: Trigonal/Hexagonal, typically occurring in elongated prismatic crystals with vertical striations. Cleavage: Indistinct. Specific gravity: 3.0-3.2.

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

Identified March 16, 2026More mineral →

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Physical properties

Formation & geological history

Formed primarily in pegmatites and metamorphic rocks like schists and marbles through hydrothermal processes. Most common in granite pegmatites. High concentrations found in specimens dating from the Archean to the Cenozoic era.

Uses & applications

Predominantly used as a semi-precious gemstone in jewelry and for metaphysical or ornamental collections. Due to its piezoelectric properties, it has historical use in pressure gauges and early scientific instruments.

Geological facts

Black tourmaline is unique because it can become electrically charged when heated (pyroelectricity) or under pressure (piezoelectricity). 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 characteristic 'rounded triangle' cross-section and deep vertical striations along the length of the crystal. Commonly found in Brazil, Namibia, and the United States (California/Maine). Collectors look for shiny, undamaged termination points.

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Epidote

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

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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)]

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Epidote

Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)

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