gemstone

Polished moss agate

Moss agate, a variety of chalcedony (microcrystalline quartz, SiO₂)

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent gray-white to clear chalcedony with green, black, or brown dendritic inclusions, typically glassy to waxy luster and no visible cleavage. The pictured pieces are tumbled or polished fragments.

Identified August 24, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater deposits chalcedony in volcanic cavities, incorporating manganese- or iron-rich dendritic inclusions; deposits are generally associated with Cenozoic volcanic rocks. Common sources include Montana and Wyoming (USA), India, Brazil, Uruguay, and Australia.

Uses & applications

Used for cabochons, beads, carvings, décor, and collecting; durable enough for everyday jewelry but less valuable than transparent crystalline quartz gems.

Geological facts

Its “moss” patterns are mineral inclusions, not organic moss or fossils; dendritic markings commonly reflect manganese or iron oxides.

Field identification & locations

Identify by its waxy translucent body, irregular branching inclusions, lack of cleavage, and quartz-like hardness; glass scratches more easily. Exact variety may also be dendritic or plume agate.