mineral
Black tourmaline (schorl)
Schorl, NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄
AI-generated identification · may be incorrectHardness 7–7.5 Mohs; opaque black with vitreous to resinous luster and typically striated, elongated crystals. Trigonal crystal structure; cleavage indistinct, fracture uneven to conchoidal; specific gravity about 3.1–3.3.
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Physical properties
Hardness 7–7.5 Mohs; opaque black with vitreous to resinous luster and typically striated, elongated crystals. Trigonal crystal structure; cleavage indistinct, fracture uneven to conchoidal; specific gravity about 3.1–3.3.
Formation & geological history
Forms in boron-rich granitic pegmatites and some metamorphic rocks as magma cools and crystallizes. Commonly associated with late-stage pegmatite minerals; specimens may be millions to billions of years old.
Uses & applications
Collected as mineral specimens and used in jewelry, usually as polished beads or cabochons. Also used in mineralogical study and, historically, as a source of boron-bearing material.
Geological facts
Schorl is the most common tourmaline species and gives the tourmaline group much of its characteristic black color.
Field identification & locations
Look for opaque, deeply black crystals with lengthwise striations and a triangular or rounded-triangular cross-section; common sources include Brazil, Afghanistan, Pakistan, and the United States. The pictured pieces appear consistent with fractured schorl crystals.
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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
Unidentified pink-and-gray mineral or rock specimen
Undetermined; the image is too blurry for reliable identification
mineral