mineral

Tumbled brown agate or jasper

Microcrystalline quartz (SiO₂), likely chalcedony with iron-oxide impurities

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; rounded, polished surface with waxy to glassy luster, brown/olive-gray color, and faint translucent banding or cloudy internal structure. Quartz has trigonal crystal structure but is cryptocrystalline here; cleavage is absent and fracture is conchoidal.

Identified August 29, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rock, with iron oxides producing brown coloration; commonly Paleozoic to Cenozoic in age depending on locality. Tumbled and polished commercially.

Uses & applications

Used for cabochons, beads, worry stones, carvings, and decorative specimens; not generally used as a construction stone in this form.

Geological facts

Agate is banded chalcedony, while jasper is more opaque and impurity-rich; many specimens grade between the two and cannot be identified precisely from a photograph.

Field identification & locations

Commonly found in volcanic terrains, especially Brazil, Uruguay, Mexico, India, Madagascar, and the western United States. Check for translucency, conchoidal fracture, hardness sufficient to scratch glass, and lack of bubbling or uniform glassy texture.