mineral

Tumbled chalcedony (likely agate or jasper)

Microcrystalline quartz, SiO₂ (chalcedony)

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; gray, blue-gray, cream, and brown coloration with a waxy to vitreous luster. Cryptocrystalline quartz has no visible cleavage and typically conchoidal fracture; the rounded shape appears tumbled or naturally water-worn.

Identified August 19, 2026More mineral →

Explore Tumbled chalcedony (likely agate or jasper) in the encyclopedia →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities, fractures, or vesicles in volcanic rocks, precipitating microscopic quartz fibers and occasional banding. Formation ages vary widely, commonly from Paleozoic to Cenozoic deposits.

Uses & applications

Used for cabochons, beads, carvings, lapidary specimens, and ornamental stone; durable pieces may be polished for jewelry.

Geological facts

Chalcedony is an aggregate of quartz and moganite, and its varieties include agate, jasper, carnelian, and chrysoprase.

Field identification & locations

Identify by its translucent-to-opaque appearance, waxy surface, hardness, and lack of cleavage; agate usually shows curved bands, while jasper is more opaque and earthy. Common sources include Brazil, Uruguay, India, Madagascar, Mexico, and the western United States.