mineral
Likely black tourmaline (schorl)
Schorl, NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄
AI-generated identification · may be incorrectDark blue-black, vitreous to submetallic luster, with prominent lengthwise striations; Mohs hardness 7–7.5 and specific gravity about 3.2. The image does not show enough detail to confirm mineral identity or crystal form.
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Physical properties
Dark blue-black, vitreous to submetallic luster, with prominent lengthwise striations; Mohs hardness 7–7.5 and specific gravity about 3.2. The image does not show enough detail to confirm mineral identity or crystal form.
Formation & geological history
Schorl crystallizes in boron-rich granitic pegmatites and hydrothermal veins, commonly during late-stage magma cooling; deposits range from Precambrian to recent geological settings.
Uses & applications
Used as a collector specimen and, when well-formed, in jewelry; tourmaline varieties are also studied for their electrical properties.
Geological facts
Tourmaline can become electrically polarized when heated or rubbed, a property known as pyroelectricity and piezoelectricity.
Field identification & locations
Look for a hard, black crystal with parallel lengthwise grooves and a roughly triangular cross-section; common sources include Brazil, Afghanistan, and the United States. The pictured piece may instead be another dark, striated mineral, so identification is tentative.
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Sandstone (with potential mineral staining/concretions)
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Epidote
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Pegmatite with Tourmaline and Quartz
Igneous Pegmatite
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Granite
Granite (Phaneritic intrusive igneous rock)
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