mineral
Likely black tourmaline (schorl), shown as a rough fragment and polished cabochon
Schorl, NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄
AI-generated identification · may be incorrectTypically black with a vitreous luster and hexagonal/trigonal crystal structure; Mohs hardness 7–7.5, specific gravity about 3.0–3.3, and poor cleavage. The image alone does not confirm the identification; the smooth oval piece may be another black gemstone.
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Physical properties
Typically black with a vitreous luster and hexagonal/trigonal crystal structure; Mohs hardness 7–7.5, specific gravity about 3.0–3.3, and poor cleavage. The image alone does not confirm the identification; the smooth oval piece may be another black gemstone.
Formation & geological history
Forms in boron-rich granitic pegmatites and some metamorphic rocks as magma cools; crystals range widely in geological age.
Uses & applications
Used as a collectible mineral and, when attractive and durable, cut into cabochons or beads for jewelry.
Geological facts
Schorl is the most common tourmaline species and often forms long, striated prismatic crystals.
Field identification & locations
Look for a black, glassy appearance and lengthwise striations on rough crystals; common in pegmatites worldwide, including Brazil, Afghanistan, and the United States. Confirm with hardness and mineral testing rather than appearance alone.
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Gneiss or Schist
Gneiss or Mica Schist with Garnet
Metamorphic
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
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
Septarian Pebble
Septarian nodule / Concretion
sedimentary