mineral

Tumbled agate/chalcedony pebble

Microcrystalline quartz (SiO₂), likely brown/banded agate or jasper

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; brown, reddish, and translucent gray zones; waxy to vitreous luster; cryptocrystalline quartz with no visible cleavage; specific gravity about 2.6.

Identified September 11, 2026More mineral →

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Physical properties

Hardness about 6.5–7 Mohs; brown, reddish, and translucent gray zones; waxy to vitreous luster; cryptocrystalline quartz with no visible cleavage; specific gravity about 2.6.

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing layered chalcedony and quartz over long periods, commonly during the Cenozoic or older volcanic episodes. Its smooth shape indicates natural stream/beach abrasion or tumbling.

Uses & applications

Used as a decorative pebble, cabochon, bead, and lapidary material; attractive pieces may be polished for jewelry or collecting.

Geological facts

Agate is a variety of chalcedony distinguished by translucency and banding, while jasper is more opaque and impurity-rich; this specimen appears partly translucent but lacks enough detail for a precise variety identification.

Field identification & locations

Common in volcanic terrains and gravel beaches, especially Oregon, Washington, California, Brazil, Uruguay, India, and Madagascar. Field tests include scratching glass, resisting steel scratching, and showing translucency at thin edges; avoid confusing it with slag or colored glass.