fossil

Agatized fossil fragment, possibly silicified coral

Chalcedony (microcrystalline SiO₂) replacing carbonate fossil material

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; pale gray, cream, tan, and translucent brown with waxy to dull luster. Irregular banding, cellular or fossil-like textures, and conchoidal fracture are visible; crystal structure is cryptocrystalline quartz, with no obvious cleavage.

Identified August 9, 2026More fossil →

Explore Agatized fossil fragment, possibly silicified coral in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Likely formed when silica-rich groundwater replaced or filled a carbonate shell/coral structure during diagenesis, preserving its texture. The precise geological age cannot be determined from the photograph; such silicified fossils occur in rocks from many Paleozoic to Cenozoic formations.

Uses & applications

Collected as a lapidary and fossil specimen; suitable pieces may be cut or polished for display, cabochons, or ornaments. Common examples generally have modest commercial value.

Geological facts

The preserved ridges and cavities may represent coral, shell, or another porous fossil, but the image is insufficient for a confident taxonomic identification.

Field identification & locations

Look for repeating biological chambers, pores, or growth bands, a glassy waxy fracture, and hardness sufficient to scratch ordinary glass; vinegar or acid testing should be avoided if preservation is uncertain. Common in silica-rich limestone and volcanic-ash-bearing sedimentary formations worldwide.