mineral

Tumbled smoky quartz (probable)

Quartz, silicon dioxide (SiO₂), colored by irradiation and trace aluminum

AI-generated identification · may be incorrect

Hardness 7 Mohs; translucent gray-brown to smoky black, with a vitreous luster and conchoidal fracture. Quartz is trigonal and lacks cleavage; the rounded shape indicates tumbling and polishing.

Identified September 5, 2026More mineral →

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Physical properties

Hardness 7 Mohs; translucent gray-brown to smoky black, with a vitreous luster and conchoidal fracture. Quartz is trigonal and lacks cleavage; the rounded shape indicates tumbling and polishing.

Formation & geological history

Forms in silica-rich hydrothermal veins, pegmatites, and cavities in igneous rocks, commonly during Precambrian to younger geological events. The specimen’s exact locality and age cannot be determined from the photograph.

Uses & applications

Used as a decorative and lapidary stone, in jewelry, and by collectors; quartz also has major industrial uses in glass, electronics, and abrasives.

Geological facts

The dark color results mainly from natural radiation affecting trace impurities, not from a separate mineral. It may be confused with smoky glass, obsidian, or dark chalcedony.

Field identification & locations

Look for glassy luster, conchoidal edges, and the ability to scratch ordinary glass; quartz should not be scratched by a steel knife. Common sources include Brazil, Madagascar, Switzerland, and the United States.