mineral

Tumbled black stone, likely black tourmaline or obsidian

Schörl tourmaline: NaFe3Al6(BO3)3Si6O18(OH)4, or volcanic glass (obsidian: mainly SiO2)

AI-generated identification · may be incorrect

Smooth, highly polished, black, opaque, and glassy-to-waxy; the rounded form indicates tumbling. Hardness is approximately 7–7.5 for tourmaline or 5–5.5 for obsidian; crystal structure cannot be confirmed from this blurred image.

Identified September 14, 2026More mineral →

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Physical properties

Formation & geological history

Black tourmaline forms in granitic pegmatites and metamorphic rocks; obsidian forms when silica-rich lava cools rapidly, generally during the Quaternary or older volcanic episodes.

Uses & applications

Used as a decorative tumbled stone, carving material, and collector specimen; black tourmaline is also used in jewelry. Obsidian can be knapped into very sharp tools.

Geological facts

The image does not show diagnostic crystal faces or conchoidal fracture, so exact identification is uncertain. Its uniformly rounded, glossy appearance is also compatible with dyed or coated stone.

Field identification & locations

Near 10.6°N, 61.1°W (Trinidad), dark tumbled material could be imported; natural obsidian is not a typical local Trinidad rock. Test gently with a steel file: obsidian may scratch more easily, while tourmaline generally resists; a streak test and specific gravity would help.