mineral
Likely black tourmaline (schorl)
Schorl, NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄
AI-generated identification · may be incorrectDark brown-black, vitreous to dull, with lengthwise striations typical of tourmaline; Mohs hardness 7–7.5 and a trigonal crystal structure. The specimen appears broken or partly worn, so identification from the photo is provisional.
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Physical properties
Dark brown-black, vitreous to dull, with lengthwise striations typical of tourmaline; Mohs hardness 7–7.5 and a trigonal crystal structure. The specimen appears broken or partly worn, so identification from the photo is provisional.
Formation & geological history
Tourmaline crystallizes in boron-rich granitic pegmatites and related hydrothermal rocks, commonly during late-stage magma cooling; it occurs in rocks of many geological ages.
Uses & applications
Used as a mineral specimen and, when transparent and attractive, as a gemstone; black schorl is also collected and occasionally used decoratively.
Geological facts
Schorl is the most common tourmaline species and is typically opaque and iron-rich.
Field identification & locations
Look for a hard, dark crystal with pronounced parallel grooves along its length; common sources include Brazil, Afghanistan, Pakistan, and the United States. A scratch test or mineralogical analysis would help confirm the identification.
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