mineral
Polished smoky quartz or brown chalcedony pebble
Silicon dioxide (SiO₂), likely quartz/chalcedony with iron-oxide inclusions
AI-generated identification · may be incorrectTranslucent brown to black with a glassy-to-waxy luster, conchoidal-looking fractures, and rounded polishing. Quartz hardness is Mohs 7; chalcedony is cryptocrystalline quartz with no visible cleavage and specific gravity near 2.6.
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Physical properties
Translucent brown to black with a glassy-to-waxy luster, conchoidal-looking fractures, and rounded polishing. Quartz hardness is Mohs 7; chalcedony is cryptocrystalline quartz with no visible cleavage and specific gravity near 2.6.
Formation & geological history
Formed when silica-rich fluids precipitated quartz or chalcedony in cavities and fractures, with iron producing the brown coloration; the geological age cannot be determined from the image. Its smooth shape indicates water-worn and/or tumbled material.
Uses & applications
Used as a lapidary cabochon, ornamental stone, bead, or collector specimen; it has little industrial value at this small size.
Geological facts
The dark bands and metallic-looking areas may reflect iron oxides or inclusions rather than a separate metal mineral. A glassy translucent edge and resistance to scratching help distinguish quartz from glass or softer stones.
Field identification & locations
Commonly found in silica-rich volcanic rocks, hydrothermal veins, and alluvial gravels; test cautiously with a steel file or quartz point, since surface coatings can alter results. Likely localities include agate and quartz regions worldwide.
