mineral

Schorl (Black Tourmaline)

Sodium iron aluminum borosilicate (NaFe3Al6(BO3)3Si6O18(OH)4)

Hardness: 7-7.5; Color: Inky black to deep brownish black; Luster: Vitreous to sub-metallic; Crystal Structure: Trigonal (often hexagonal prisms with vertical striations); Cleavage: Indistinct; Specific Gravity: 3.0-3.3

Hardness: 7-7
Color: Inky black to deep brownish black
Luster: Vitreous to sub-metallic

Identified July 3, 2026More mineral →

Explore Schorl (Black Tourmaline) in the encyclopedia →

Identify your own rocks.

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

App Store Google Play

Physical properties

Formation & geological history

Primary formation occurs in granitic pegmatites and accessory within metamorphic rocks like schists and gneisses, forming through hydrothermal fluids rich in boron.

Uses & applications

Used primarily as a gemstone for collectors and metaphysical purposes; historically used in scientific instruments for its pyroelectric and piezoelectric properties.

Geological facts

Black tourmaline is both pyroelectric (generates electricity when heated) and piezoelectric (generates electricity when squeezed). It is the most common member of the tourmaline group, making up nearly 95% of all tourmaline found in nature.

Field identification & locations

Identify by its elongated prismatic crystal shape with three-sided cross-sections and heavy vertical striations. Found in Brazil, Namibia, Madagascar, and the US (Maine/California). It is opaque and does not transmit light even on thin edges.

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