mineral
Black tourmaline (schorl)
Schorl, NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄
AI-generated identification · may be incorrectBlack, vitreous luster, strongly lengthwise-striated prismatic crystal with uneven fracture; Mohs hardness 7–7.5. Trigonal crystal system; no distinct cleavage; specific gravity about 3.0–3.3.
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Physical properties
Black, vitreous luster, strongly lengthwise-striated prismatic crystal with uneven fracture; Mohs hardness 7–7.5. Trigonal crystal system; no distinct cleavage; specific gravity about 3.0–3.3.
Formation & geological history
Forms in boron-rich granitic pegmatites and metamorphic rocks as magma cools and fluids crystallize; individual crystals may be millions to billions of years old.
Uses & applications
Used as a collectible mineral and occasionally as a black gemstone; tourmaline is also valued for its piezoelectric and pyroelectric properties.
Geological facts
Schorl is the most common tourmaline species and is typically opaque and iron-rich.
Field identification & locations
The black color and prominent parallel grooves strongly suggest schorl. Common sources include Brazil, Afghanistan, Pakistan, and the United States; confirm with hardness and mineral testing.
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Other mineral specimens
Gneiss or Schist
Gneiss or Mica Schist with Garnet
Metamorphic
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Tumbled granite
Granite, a coarse-grained felsic intrusive igneous rock
igneous
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Pegmatite with Tourmaline and Quartz
Igneous Pegmatite
igneous
Granite
Granite (Phaneritic intrusive igneous rock)
igneous