mineral

Black tourmaline (schorl)

Schorl, a sodium–iron tourmaline; approximate formula NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄

AI-generated identification · may be incorrect

Typically Mohs 7–7.5, black with a vitreous to dull luster and trigonal crystals; tourmaline commonly shows lengthwise striations and poor cleavage. The pictured rough, dark fragment is consistent with schorl, though the photo alone cannot confirm the species.

Identified October 8, 2026More mineral →

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Physical properties

Formation & geological history

Forms in boron-rich granitic pegmatites and some metamorphic rocks as magma or hot fluids crystallize; deposits range from Precambrian to geologically recent.

Uses & applications

Collected as a mineral specimen and sometimes used in beads or jewelry; industrial use is limited.

Geological facts

Tourmaline crystals are often strongly pleochroic, appearing different shades when viewed along different directions.

Field identification & locations

Look for black, elongated crystals with parallel grooves and a vitreous luster in pegmatites; common sources include Brazil, Afghanistan, Pakistan, and the United States. Small rough pieces typically sell for about $2–$20, depending on crystal quality and locality.