mineral
Black tourmaline (schorl), likely
Schorl, a sodium–iron tourmaline; approximate formula NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄
AI-generated identification · may be incorrectOpaque black, vitreous to dull luster, with lengthwise striations and an apparent prismatic habit. Tourmaline is Mohs 7–7.5, trigonal, and has poor cleavage; the photo alone cannot confirm the identification.
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Physical properties
Opaque black, vitreous to dull luster, with lengthwise striations and an apparent prismatic habit. Tourmaline is Mohs 7–7.5, trigonal, and has poor cleavage; the photo alone cannot confirm the identification.
Formation & geological history
Typically crystallizes in boron-rich granitic pegmatites and metamorphic rocks as magma cools; specimens may range from ancient to geologically recent.
Uses & applications
Used as a collector mineral and occasionally in jewelry; tourmaline varieties are also valued as gemstones.
Geological facts
Tourmaline crystals can become electrically charged when heated or rubbed (pyroelectric and piezoelectric effects).
Field identification & locations
Check for a triangular or rounded-triangular cross-section and strong longitudinal grooves; common sources include Brazil, Afghanistan, Pakistan, and parts of the United States. A clear view or simple tests would help distinguish it from other black minerals.
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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