fossil

Polished fossil shell or crinoid fragment

Likely calcitic fossil, possibly a bivalve shell; exact identification requires clearer detail

AI-generated identification · may be incorrect

Pale gray-white, translucent to opaque, with curved layered growth lines and a smooth polished surface. Likely calcite (Mohs 3), vitreous to pearly luster, with poor cleavage; reacts with dilute hydrochloric acid.

Identified September 15, 2026More fossil →

Explore Polished fossil shell or crinoid fragment 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

A marine carbonate fossil formed when shell material was buried and preserved, commonly during Paleozoic–Mesozoic sedimentation, then later weathered or polished. The image does not show enough diagnostic anatomy for a precise age.

Uses & applications

Primarily a decorative or educational specimen; polished fossil pieces may be used in jewelry, cabochons, and collections. It has little commercial value unless exceptionally well-preserved or from a documented locality.

Geological facts

The visible concentric ridges resemble shell growth lines, while the internal curved markings may represent fossil structure or surface fractures. Calcite fossils commonly become translucent when thin or polished.

Field identification & locations

Look for symmetrical shell geometry, growth lines, and acid effervescence; hardness testing and locality information help distinguish it from quartz or glass. Common in limestone and other marine sedimentary rocks worldwide.