mineral
Black tourmaline (schorl)
Schorl, NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄
AI-generated identification · may be incorrectLikely a small, dark brown-black tourmaline fragment with a vitreous-to-submetallic luster and lengthwise striations. Mohs hardness 7–7.5; trigonal crystals, usually with no prominent cleavage. Identification from the photo is tentative.
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Physical properties
Likely a small, dark brown-black tourmaline fragment with a vitreous-to-submetallic luster and lengthwise striations. Mohs hardness 7–7.5; trigonal crystals, usually with no prominent cleavage. Identification from the photo is tentative.
Formation & geological history
Tourmaline commonly crystallizes in boron-rich granitic pegmatites and hydrothermal veins, often during late-stage magma cooling. Such deposits span a wide range of geological ages.
Uses & applications
Gem-quality material is cut for jewelry; common schorl is collected and used decoratively, with limited industrial use.
Geological facts
Tourmaline crystals are commonly strongly striated along their length and can become electrically charged when heated or rubbed.
Field identification & locations
Look for a hard, lustrous black crystal with parallel lengthwise grooves and an irregular or conchoidal break; commonly found in pegmatites worldwide. The small size and image alone do not confirm the identification.
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