mineral
Polished moss agate cabochon
Chalcedony (microcrystalline quartz, SiO₂) with chlorite/iron-oxide inclusions
AI-generated identification · may be incorrectHardness 6.5–7 Mohs; translucent to opaque green, gray, and cream with a waxy to vitreous luster. Fibrous microcrystalline quartz lacks visible cleavage; the specimen is cut and polished into a freeform cabochon.
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Physical properties
Hardness 6.5–7 Mohs; translucent to opaque green, gray, and cream with a waxy to vitreous luster. Fibrous microcrystalline quartz lacks visible cleavage; the specimen is cut and polished into a freeform cabochon.
Formation & geological history
Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, while chlorite or iron minerals create the moss-like patterns. Most material is Cenozoic to Mesozoic, depending on locality.
Uses & applications
Used for cabochons, jewelry, ornamental slabs, and lapidary collecting; value is generally modest unless the pattern and polish are exceptional.
Geological facts
The green “moss” is usually mineral inclusion rather than organic material. Although commonly called moss agate, it is chalcedony rather than true agate when distinct banding is absent.
Field identification & locations
Identify by its glassy/waxy polish, quartz-like hardness, lack of cleavage, and branching green inclusions; common sources include Montana and Oregon, USA, India, Brazil, and Central Europe. A steel file should not scratch it easily, while quartz can scratch glass.
