mineral

Tumbled agate (probable moss or dendritic agate)

Microcrystalline quartz, SiO₂, with iron/manganese dendritic inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7; translucent gray-brown to amber with dark branching or cloudy inclusions, waxy-to-glassy luster, and no visible cleavage. Agate commonly has cryptocrystalline quartz structure and specific gravity around 2.6.

Identified August 11, 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 long periods, commonly during the Cenozoic or older volcanic episodes. The rounded shape indicates human tumbling and polishing.

Uses & applications

Used for inexpensive jewelry, cabochons, ornaments, lapidary work, and collector specimens.

Geological facts

Branching dark patterns may be manganese- or iron-oxide dendrites rather than fossils or true plant material.

Field identification & locations

Identify by its translucency, smooth waxy polish, conchoidal fracture, and resistance to scratching by steel; it should not scratch glass easily unless quartz-rich. Common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the western United States.