mineral

Dendritic agate (moss agate-like chalcedony)

Microcrystalline quartz, SiO₂, with manganese/iron-oxide dendrites

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; milky white to gray chalcedony with black branching, fern-like inclusions, waxy to vitreous luster, cryptocrystalline structure, and no cleavage. The dark patterns are mineral dendrites rather than fossils.

Identified September 17, 2026More mineral →

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Physical properties

Formation & geological history

Silica-rich groundwater filled cavities and fractures, forming chalcedony; manganese or iron oxides later crystallized in branching patterns. It is generally a young-to-ancient secondary vein or cavity deposit, commonly associated with volcanic rocks.

Uses & applications

Cut and polished for cabochons, slabs, carvings, ornaments, and lapidary collections; typically not used structurally because it occurs in small pieces.

Geological facts

Despite the name “moss agate,” this material is not true agate unless it has distinct banding; dendritic chalcedony is often marketed broadly as dendritic or moss agate.

Field identification & locations

Identify by its translucent milky chalcedony body, glassy/waxy polish, conchoidal fracture, and delicate branching inclusions. Common sources include India, Brazil, Uruguay, Mexico, and the United States.