fossil

Fossilized coral fragment

Fossil coral, commonly colonial scleractinian coral (order Scleractinia); exact genus indeterminate

AI-generated identification · may be incorrect

Small tan-brown fragment with dense honeycomb-like corallite patterns and pale mineral infilling; fossil coral is commonly calcite or silica-replaced. Original calcite/aragonite hardness was about Mohs 3–4, while silicified material may reach 6–7; dull to slightly waxy luster and no obvious cleavage.

Identified August 29, 2026More fossil →

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Physical properties

Formation & geological history

A colonial coral skeleton accumulated in a shallow tropical marine reef, was buried, lithified, and variably mineralized during diagenesis. Its precise geological age cannot be determined from the photograph; fossil corals range from Paleozoic to modern-era deposits.

Uses & applications

Used as a teaching specimen, collectible, lapidary material, and occasionally in cabochons or decorative pieces. Avoid jewelry claims unless provenance and treatment are known.

Geological facts

The repeated polygonal cups are individual corallites, each once occupied by a coral polyp. Patterned fossil coral can resemble agate or engineered stone when polished.

Field identification & locations

Identify it by the regular corallite honeycomb structure, unlike random crystal banding in agate; dilute acid may fizz if calcitic, though testing can damage it. Common in uplifted ancient reef limestones worldwide, including Florida, Indonesia, Australia, and the Caribbean.