mineral

Tumbled agate or chalcedony

Microcrystalline quartz (SiO₂), likely brown/orange chalcedony or agate

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; waxy to vitreous luster, translucent brown-golden coloration, and no obvious cleavage. The apparent white ridges may be natural banding, fractures, or surface alteration; crystal structure is cryptocrystalline quartz.

Identified August 11, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, often developing concentric bands over long periods during the Cenozoic or older volcanic episodes. Exact age and locality cannot be determined from the image.

Uses & applications

Used for cabochons, beads, carvings, tumbled stones, ornaments, and occasionally abrasive or decorative material. Its value is mainly aesthetic and depends on color, translucency, pattern, and polish.

Geological facts

Agate is a variety of chalcedony distinguished by visible banding or patterned silica growth; plain chalcedony may lack bands. The specimen appears naturally rounded or partly shaped and may have been tumbled.

Field identification & locations

Look for glassy-to-waxy luster, hardness sufficient to scratch ordinary glass, conchoidal fracture, and lack of cleavage; a steel blade should not scratch it easily. Common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the western United States.