mineral

Polished moss agate / dendritic agate

Microcrystalline quartz (SiO₂) with iron- and manganese-oxide inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent to opaque gray-white chalcedony with dark green-black, brown, and reddish inclusions; vitreous to waxy luster; cryptocrystalline structure with no cleavage. The rounded shape indicates tumbling or polishing.

Identified August 19, 2026More mineral →

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Physical properties

Formation & geological history

Silica-rich groundwater filled cavities and fractures in volcanic rock, depositing chalcedony around mineral inclusions; iron and manganese produced the mossy or dendritic patterns. Formation is generally Cenozoic to older, depending on its host volcanic material.

Uses & applications

Used for cabochons, beads, decorative stones, and lapidary collections; polished pieces have modest jewelry value.

Geological facts

Despite its plant-like patterns, moss agate contains no organic moss. Color and pattern arise mainly from chlorite, hornblende, iron oxides, or manganese oxides.

Field identification & locations

Identify by translucent chalcedony, waxy surface, irregular branching inclusions, and lack of obvious quartz crystal faces or cleavage; common sources include India, Brazil, Uruguay, the United States, and Madagascar.