mineral
Black Tourmaline (Schorl)
Schorl (NaFe2+3Al6(Si6O18)(BO3)3(OH)3OH)
Hardness: 7-7.5 (Mohs), Color: Deep black, Luster: Vitreous to sub-metallic, Crystal Structure: Trigonal (striated prisms), Cleavage: Indistinct, Specific Gravity: 3.0-3.2
- Hardness
- 7-7
Identified More mineral →
Explore Black Tourmaline (Schorl) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7-7.5 (Mohs), Color: Deep black, Luster: Vitreous to sub-metallic, Crystal Structure: Trigonal (striated prisms), Cleavage: Indistinct, Specific Gravity: 3.0-3.2
Formation & geological history
Typically forms in granitic pegmatites, hydrothermal veins, and metamorphic rocks such as mica schists. It is rich in boron and iron, forming during the late stages of magma crystallization.
Uses & applications
Commonly used in metaphysical practices for protection and grounding, as an ore for boron, in scientific instruments due to its piezoelectric properties, and as jewelry for collectors.
Geological facts
Tourmaline is both pyroelectric (develops charge when heated) and piezoelectric (develops charge under pressure). In the 1700s, Dutch traders used it to pull ash from their pipes, calling it 'aschentrekker'.
Field identification & locations
Identified in the field by its characteristic long, needle-like or prismatic crystals with vertical striations and its distinct triangular or rounded-triangular cross-section. Commonly found in Brazil, Namibia, and the USA.
More like this
Other mineral specimens
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Schist
Schist
Metamorphic
Sandstone with Mineral Veining or Crust
Sedimentary Sandstone (mostly SiO2 with Fe2O3 tinting)
sedimentary
Potassium Feldspar (Orthoclase)
Orthoclase (KAlSi3O8)
mineral
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Nephrite Jade
Nephrite
Mineral/Rock