mineral

Black Tourmaline

Schorl (Sodium Iron Aluminum Borosilicate Hydroxide), NaFe3Al6(BO3)3Si6O18(OH)4

Hardness: 7-7.5 on Mohs scale; Color: Jet black; Luster: Vitreous to sub-metallic; Crystal Structure: Trigonal (often long, striated columnar crystals); Cleavage: Indistinct; Specific Gravity: 3.0-3.2

Hardness: 7-7
Color: Jet black
Luster: Vitreous to sub-metallic

Identified March 23, 2026More mineral →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed in granitic pegmatites, hydrothermal veins, and metamorphic rocks such as schists. They are common in late-stage igneous environments where boron is concentrated. Found in geological formations ranging from Precambrian to recent periods.

Uses & applications

Extensively used in jewelry (tumbled or faceted), metaphysical or 'healing' crystals, and industrial applications due to its piezoelectric properties (used in pressure gauges and optical instruments).

Geological facts

Black tourmaline is piezoelectric, meaning it can generate an electrical charge when mechanically stressed. It is the most common member of the tourmaline group, accounting for 95% of all tourmaline in nature. In Victorian times, it was frequently used as mourning jewelry.

Field identification & locations

Identify in the field by its deep black color, high hardness (cannot be scratched by steel), and characteristic longitudinal striations (parallel lines) along the crystal faces. Common locations include Brazil, Namibia, Madagascar, and San Diego County, USA.

Other mineral specimens

See all

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

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

Epidote

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

mineral