mineral

Small dark tumbled stone, likely black tourmaline

Possibly schorl, NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄; identification uncertain from the image

AI-generated identification · may be incorrect

Opaque, black to dark brown, with a subdued luster and rounded, polished surfaces. If schorl, hardness is 7–7.5 Mohs, with a trigonal crystal structure and no distinct cleavage; the image is too small to confirm diagnostic features.

Identified October 7, 2026More mineral →

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Physical properties

Formation & geological history

Black tourmaline forms in boron-rich granitic pegmatites and metamorphic rocks over a wide range of geological ages. Tumbling smooths the natural material without changing its geological origin.

Uses & applications

Tumbled stones are commonly sold for collecting, crafts, and jewelry; tourmaline is also used as a gemstone.

Geological facts

The visible specimen is too small and featureless for reliable mineral identification; other dark minerals or rocks could look similar.

Field identification & locations

Check for lengthwise striations or a triangular cross-section to support tourmaline identification; hardness testing should be done cautiously. Tourmaline is found worldwide, including Brazil, Afghanistan, and the United States.