mineral

Polished fossiliferous agate

Chalcedony (microcrystalline SiO₂), likely fossil-bearing agate

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; brown, honey, cream, and gray banding with waxy to vitreous luster. Microcrystalline quartz forms concentric bands, cavities, and fossil-like orbicular structures; no obvious cleavage, specific gravity about 2.6.

Identified August 23, 2026More mineral →

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Physical properties

Formation & geological history

Silica-rich groundwater deposited chalcedony and quartz in cavities of volcanic rock, while the circular textures may preserve replaced shells or microbial structures. Formation is generally Cenozoic to older, depending on locality.

Uses & applications

Used as a lapidary stone for cabochons, carvings, and display specimens; attractive fossil-patterned pieces are collected rather than used structurally.

Geological facts

The rounded “eyes” and cellular patterns are characteristic of fossil agate or orbicular agate, though similar patterns can arise from mineralized cavities and Liesegang banding.

Field identification & locations

Identify by its fine concentric banding, glassy/waxy surface, hardness, and lack of fizz in dilute acid. Common sources include Indonesia, Madagascar, Brazil, Mexico, and the western United States.