gemstone

Polished mossy dendritic agate

Microcrystalline quartz (chalcedony), SiO₂, with iron/manganese dendrites and possible inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; opaque to translucent gray-blue, cream, brown, and reddish zones; waxy to vitreous luster; cryptocrystalline quartz with no visible cleavage and conchoidal fracture. The smooth shape is tumbled and polished.

Identified September 15, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, depositing chalcedony in layers; colored dendrites commonly develop from manganese or iron oxides. Formation is generally Cenozoic to older, depending on the host volcanic rock.

Uses & applications

Used for cabochons, beads, carvings, and decorative objects; ordinary pieces have modest jewelry value.

Geological facts

Its branching brown markings can resemble moss or miniature landscapes, though they are mineral inclusions rather than fossils or plant material.

Field identification & locations

Identify by its glassy/waxy polish, very fine quartz texture, hardness, and irregular dendritic inclusions; it commonly occurs in volcanic terrains, including Brazil, India, Madagascar, Mexico, and the western United States. A steel file should not easily scratch it.