mineral

Schorl (Black Tourmaline)

Sodium Iron Aluminum Borosilicate Hydroxide; NaFe2+3Al6Si6O18(BO3)3(OH)3OH

Hardness: 7-7.5 (Mohs); Color: Jet black; Luster: Vitreous to sub-metallic; Crystal structure: Trigonal/Hexagonal with vertical striations (heavy ribbing); 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

Forms primarily in granitic pegmatites, hydrothermal veins, and metamorphic rocks such as schists and gneisses. It forms from boron-rich fluids during the final stages of magma crystallization.

Uses & applications

Used industrially in pressure gauges (due to piezoelectric properties), as an ore of boron, and widely in the gemstone/jewelry trade and metaphysical collecting markets.

Geological facts

Schorl is both pyroelectric (generates electricity when heated) and piezoelectric (generates electricity under pressure). It was reportedly used by early Dutch traders to pull ash out of meerschaum pipes, earning it the nickname 'Aschentrekker' (ash puller).

Field identification & locations

Identify in the field by its distinct triangular or rounded-triangular cross-section and deep vertical striations. Commonly found in Brazil, Namibia, and the USA (California and Maine). Look for it in coarse-grained igneous environments.

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