fossil

Fossilized coral (likely honeycomb or brain coral)

Calcitic coral skeleton; commonly Favosites or Porites-like colonial coral

AI-generated identification · may be incorrect

White to cream, porous branching or corallite structure with dull to slightly waxy luster; composed mainly of calcium carbonate (calcite or originally aragonite). Mohs hardness is about 3, with poor cleavage and specific gravity near 2.6–2.8.

Identified September 5, 2026More fossil →

Explore Fossilized coral (likely honeycomb or brain 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

A colonial coral skeleton accumulated in a shallow, warm marine reef and was later lithified and commonly recrystallized during diagenesis. The exact geological age cannot be determined from the photograph; fossil corals range from Paleozoic to recent deposits.

Uses & applications

Used as a fossil specimen, educational material, and decorative stone; rarely cut or polished for jewelry and carvings. Its porous surface makes it unsuitable for most structural construction.

Geological facts

The holes are individual corallites, each formerly occupied by a tiny coral polyp; this cellular pattern distinguishes coral from ordinary vesicular volcanic rock.

Field identification & locations

Identify it by repeated polygonal or rounded corallite chambers, often with internal radial walls, rather than random gas bubbles. Fossil coral occurs widely in limestone deposits and ancient reef regions, including the Great Lakes, Florida, the Caribbean, and Australia.