mineral

Polished moss agate cabochon

Chalcedony (microcrystalline quartz, SiO₂) with chlorite/iron-oxide inclusions

AI-generated identification · may be incorrect

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.

Identified September 12, 2026More mineral →

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Physical properties

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.