fossil

Fossilized coral or stromatoporoid

Calcitic fossil carbonate, possibly tabulate coral (order Favositida) or stromatoporoid

AI-generated identification · may be incorrect

Gray to cream, opaque, dull-to-waxy surface with rounded, irregular colonies or chambers; composed mainly of calcite (Mohs hardness 3), commonly showing faint cellular or honeycomb textures. Exact identification is limited by the image and surface weathering.

Identified August 19, 2026More fossil →

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Physical properties

Formation & geological history

A Paleozoic marine organism formed a calcium-carbonate skeleton that was later buried and mineralized, commonly during the Ordovician–Devonian (about 485–359 million years ago).

Uses & applications

Primarily a teaching, lapidary, and collecting specimen; polished fossil coral is occasionally used for decorative objects and jewelry.

Geological facts

Fossil coral can resemble agate or limestone, but coral colonies typically preserve repeated corallite tubes or polygonal chambers. Acid may produce effervescence because of calcite.

Field identification & locations

Look for regular microscopic pores, tubes, or star-like corallites on a broken or polished surface; test cautiously with a drop of dilute hydrochloric acid or vinegar. Common in Paleozoic limestone deposits worldwide, including the Great Lakes region and parts of Europe and Asia.