mineral
Likely black tourmaline (schorl)
Schorl, NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄
AI-generated identification · may be incorrectOpaque black with a vitreous to slightly dull luster and longitudinal striations; Mohs hardness 7–7.5, trigonal crystal structure, poor cleavage, and uneven fracture. The rough, small specimen is consistent with tourmaline, though identification from this image alone is uncertain.
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Physical properties
Opaque black with a vitreous to slightly dull luster and longitudinal striations; Mohs hardness 7–7.5, trigonal crystal structure, poor cleavage, and uneven fracture. The rough, small specimen is consistent with tourmaline, though identification from this image alone is uncertain.
Formation & geological history
Typically crystallizes in boron-rich granitic pegmatites and metamorphic rocks; forms as magma cools, with deposits spanning many geological ages.
Uses & applications
Used as a mineral specimen and occasionally in jewelry; black tourmaline is commonly cut or polished, while industrial use is limited.
Geological facts
Schorl is the most common tourmaline species and is strongly pleochroic in suitable crystals.
Field identification & locations
Look for black, elongated crystals with parallel lengthwise grooves and no obvious cleavage; common sources include Brazil, Africa, and the United States.
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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