mineral
Dendritic agate (moss agate-like chalcedony)
Microcrystalline quartz, SiO₂, with manganese/iron-oxide dendrites
AI-generated identification · may be incorrectHardness 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.
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Physical properties
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.
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.
