mineral

Tumbled agate/chalcedony

Microcrystalline quartz (SiO₂), likely mossy or dendritic agate with iron-oxide inclusions

AI-generated identification · may be incorrect

Mohs hardness 6.5–7; translucent milky-white to gray with brown/black inclusions, waxy to vitreous luster, cryptocrystalline structure, and no visible cleavage. The smoothly rounded surface indicates tumbling and polishing.

Identified August 19, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony and trapped iron/manganese oxides or manganese dendrites in successive layers. Agate formation commonly occurred from the Paleozoic through Cenozoic eras, depending on locality.

Uses & applications

Used for cabochons, beads, carvings, decorative stones, and inexpensive jewelry; polished pieces are popular mineral-collection specimens.

Geological facts

The dark markings may resemble moss or branching plants but are inorganic mineral inclusions. Agate is a variety of chalcedony rather than a separate mineral species.

Field identification & locations

Identify it by its translucency, very fine quartz texture, conchoidal fracture, lack of cleavage, and resistance to scratching by a steel blade; avoid testing the polished face. Common sources include Brazil, Uruguay, India, Mexico, and the United States.