mineral

Tumbled agate/chalcedony

Microcrystalline quartz (SiO₂), likely agate with iron-oxide and other mineral inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent brown, gray, cream, and greenish patches; waxy to dull luster; cryptocrystalline quartz with no cleavage, conchoidal fracture, and specific gravity about 2.6. The irregular rounded shape indicates natural weathering or tumbling.

Identified August 19, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks, depositing layered chalcedony and quartz over time; associated host rocks are commonly Cretaceous to Cenozoic volcanic formations. Exact age and locality cannot be determined from the photograph.

Uses & applications

Used for cabochons, beads, carvings, polished ornaments, and inexpensive collector specimens; agate is also used decoratively and occasionally for small industrial components.

Geological facts

Color zoning and cloudy bands reflect changing fluids and trace-element impurities during cavity filling. Green areas may represent chlorite, celadonite, or other inclusions rather than green quartz.

Field identification & locations

Look for waxy translucency, curved fracture surfaces, subtle banding, and a glass scratch test; it should not be scratched by a steel knife. Common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the western United States.