sedimentary

Eye Agate

Chalcedony (Silicon Dioxide, SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Gray, lavender, and brown concentric banding. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (hexagonal). Cleavage: None. Specific Gravity: 2.58-2.64.

Hardness: 6
Color: Gray, lavender, and brown concentric banding
Luster: Waxy to vitreous

Identified July 20, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the deposition of silica from groundwater into cavities (gas bubbles) in volcanic or sedimentary rocks. The 'eye' pattern is a result of concentric layering as silica-rich fluids cooled and solidified within the cavity.

Uses & applications

Largely used for lapidary arts, jewelry (cabochons), and collecting. In ancient times, eye agates were valued as talismans believed to protect the wearer from the 'evil eye'.

Geological facts

Agates are one of the oldest gemstones used in jewelry. The unique 'eye' patterns are highly sought after by collectors of patterned chalcedony. This specific specimen appears to be a small nodule that has been polished.

Field identification & locations

Identify by concentric circular banding and translucency when held to light. Common in Brazil, Botswana, and the Lake Superior region of the US. Field identification often requires breaking through a rough, weathered exterior.