mineral

Tumbled black stone, possibly black tourmaline

Uncertain from the photo; possible schorl (NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄)

AI-generated identification · may be incorrect

Small, polished, glossy dark specimen with rounded, irregular shape. If schorl, hardness is 7–7.5 Mohs and crystals are trigonal; the image alone cannot confirm composition or cleavage.

Identified September 27, 2026More mineral →

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Physical properties

Small, polished, glossy dark specimen with rounded, irregular shape. If schorl, hardness is 7–7.5 Mohs and crystals are trigonal; the image alone cannot confirm composition or cleavage.

Formation & geological history

If tourmaline, it crystallized in boron-rich pegmatites or metamorphic rocks, commonly during the Precambrian to much younger geologic periods. A polished surface obscures diagnostic natural crystal form.

Uses & applications

Black tourmaline is collected and used in jewelry and decorative objects; it has limited industrial use.

Geological facts

Schorl is the most common tourmaline species and is typically black due to iron. This specimen’s identity cannot be established reliably from appearance alone.

Field identification & locations

Check for elongated striated crystals, hardness, and diagnostic mineral tests; polished shape and luster are not sufficient to distinguish tourmaline from other black minerals. Tourmaline occurs worldwide, including Brazil, Afghanistan, and the United States.