gemstone

Polished agate (likely moss or plume agate)

Microcrystalline quartz, SiO₂, chiefly chalcedony with possible included iron oxides

AI-generated identification · may be incorrect

Mohs hardness 6.5–7; translucent gray-green, cream, and honey-brown zones with waxy to vitreous luster. Cryptocrystalline quartz has no visible cleavage and commonly shows curved banding or dendritic inclusions; specific gravity is about 2.6.

Identified August 30, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks, depositing chalcedony and quartz in successive layers; iron and other minerals create the colored inclusions. Individual agates may range from Cenozoic to much older, depending on the host rock.

Uses & applications

Commonly tumbled and used for cabochons, beads, carvings, ornamental objects, and paperweights; durable agate is also used for precision grinding and laboratory mortars.

Geological facts

Color patterns are produced by microscopic growth bands and mineral impurities rather than paint. “Moss agate” contains branching mineral inclusions, while “plume agate” has feathery internal patterns.

Field identification & locations

Identify by translucency, curved or plume-like internal patterns, waxy polish, and hardness sufficient to scratch glass; it is commonly found in volcanic regions worldwide, including Brazil, Uruguay, India, Mexico, and the western United States.