mineral
Likely black tourmaline (schorl)
Schorl, NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄
AI-generated identification · may be incorrectAppears opaque black and rough with a vitreous-to-dull luster; tourmaline has Mohs hardness 7–7.5 and commonly shows lengthwise striations. The small, blurry specimen does not reveal diagnostic crystal form clearly.
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Physical properties
Appears opaque black and rough with a vitreous-to-dull luster; tourmaline has Mohs hardness 7–7.5 and commonly shows lengthwise striations. The small, blurry specimen does not reveal diagnostic crystal form clearly.
Formation & geological history
Schorl crystallizes in boron-rich granitic pegmatites and metamorphic rocks as magma cools; deposits range from ancient to geologically recent, depending on the host rock.
Uses & applications
Used as a collectible mineral and occasionally in jewelry; black specimens are commonly sold as rough crystals rather than cut gems.
Geological facts
Tourmaline crystals are often strongly striated and can become electrically charged when heated or rubbed.
Field identification & locations
The dark color and apparent rough, prismatic shape suggest schorl, but the image is insufficient for a confident identification. Check for longitudinal grooves and a hard, scratch-resistant surface; tourmaline occurs worldwide, including Brazil, Africa, and the United States.
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