mineral
Possible black tourmaline (schorl)
Schorl, NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄
AI-generated identification · may be incorrectSmall, black, opaque rough fragment with a vitreous-to-dull luster; tourmaline has Mohs hardness 7–7.5 and a trigonal crystal structure. The photo lacks enough detail to confirm its characteristic lengthwise striations or crystal shape.
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Physical properties
Small, black, opaque rough fragment with a vitreous-to-dull luster; tourmaline has Mohs hardness 7–7.5 and a trigonal crystal structure. The photo lacks enough detail to confirm its characteristic lengthwise striations or crystal shape.
Formation & geological history
Schorl crystallizes in boron-rich granitic pegmatites and metamorphic rocks; such deposits formed at many geological ages. The specimen’s specific origin and age cannot be determined from the image.
Uses & applications
Used as a collector mineral and occasionally in jewelry; most black rough fragments of this size have modest value.
Geological facts
Black tourmaline is the most common tourmaline variety and commonly forms elongated, striated crystals.
Field identification & locations
Look for a hard, black crystal with parallel lengthwise grooves and a roughly triangular cross-section; common sources include Brazil, Africa, and the United States. Identification from this image is tentative—the fragment could be another dark mineral or rock.
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