fossil

Polished fossiliferous agate

Chalcedony (microcrystalline SiO₂) containing fossil fragments, likely an agatized limestone or stromatolite

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; brown, cream, gray, and reddish banding with waxy to glassy luster. The curved layers and fossil-like inclusions indicate fibrous chalcedony replacing or filling a carbonate host.

Identified August 28, 2026More fossil →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater permeates cavities or porous marine limestone, preserving and replacing shells or microbial textures; age depends on locality, commonly Paleozoic–Cenozoic. Often associated with volcanic or sedimentary silica deposits.

Uses & applications

Primarily a lapidary and collectible material, used for polished cabochons, ornaments, paperweights, and display specimens; generally unsuitable as a major construction stone.

Geological facts

Polishing accentuates concentric banding and fossil outlines. Identification as a specific fossil type or locality requires magnification, hardness testing, and geological provenance.

Field identification & locations

Look for fine parallel or concentric chalcedony bands, waxy luster, silica-level hardness, and recognizable fossil silhouettes; common sources include Brazil, Madagascar, Uruguay, Mexico, and the United States.