mineral

Polished/tumbled agate (likely carnelian or iron-stained chalcedony)

Microcrystalline quartz, SiO₂; chalcedony with iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; waxy to vitreous luster; cream, honey, orange, and reddish-brown coloration; translucent margins with cloudy banding and no visible cleavage. The orange-red areas are likely hematite/goethite staining or inclusions.

Identified August 21, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks, depositing chalcedony in layers over long periods, commonly during the Cenozoic or older volcanic episodes. Natural weathering and human tumbling/polishing produced the rounded shape.

Uses & applications

Used as an ornamental stone, cabochon, bead, carving material, and inexpensive jewelry or display specimen; also popular in lapidary work.

Geological facts

Agate is a variety of chalcedony distinguished by concentric or irregularly layered textures; iron oxidation creates the vivid orange and rust colors.

Field identification & locations

Identify by its waxy luster, curved or cloudy chalcedony banding, rounded fracture, translucency, and hardness sufficient to scratch glass. Common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the western United States.