mineral

Polished/tumbled chalcedony or agate

Microcrystalline quartz, SiO₂; likely botryoidal chalcedony with agate-like banding

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent gray-green, cream, and brown; waxy to vitreous luster; cryptocrystalline quartz with no cleavage, conchoidal fracture, and specific gravity about 2.6. The rounded surface appears naturally weathered or lightly polished.

Identified September 6, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rock, depositing chalcedony and occasional concentric agate bands. Individual specimens may range from Paleozoic to Cenozoic depending on locality.

Uses & applications

Used for cabochons, carvings, beads, lapidary specimens, and decorative stone; attractive pieces have modest jewelry and collector value.

Geological facts

Green coloration may result from included chlorite, epidote, or other minerals; brown zones commonly reflect iron oxides. Exact identification requires a close examination of banding and inclusions.

Field identification & locations

Look for waxy luster, translucent edges, curved/concentric banding, and hardness sufficient to scratch ordinary glass. Common sources include Brazil, Uruguay, India, Madagascar, Mexico, and the western United States.