sedimentary

Fossil Coral

Cnidaria Anthozoa (Fossilized)

Hardness: 3-4 (Calcite based); Color: Tan, beige, or white with dark skeletal patterns; Luster: Dull to earthy; Structure: Hexagonal or colonial pore patterns; Specific Gravity: 2.6-2.7

Hardness: 3-4 (Calcite based)
Color: Tan, beige, or white with dark skeletal patterns
Luster: Dull to earthy

Identified April 8, 2026More sedimentary →

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Physical properties

Hardness: 3-4 (Calcite based); Color: Tan, beige, or white with dark skeletal patterns; Luster: Dull to earthy; Structure: Hexagonal or colonial pore patterns; Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the replacement of organic calcium carbonate skeletons by minerals (permineralization), typically during the Devonian to Jurassic periods. Found in ancient marine sedimentary beds.

Uses & applications

Used primarily for jewelry (cabochons), interior decoration, paperweights, and as educational geological specimens.

Geological facts

Many fossil corals are hundreds of millions of years old, predating the dinosaurs. Petoskey stones from Michigan are a famous variety of fossilized colonial coral.

Field identification & locations

Identify by looking for a 'honeycomb' or 'starlike' pattern on the surface that does not wash off. They are common in areas that were once prehistoric shallow seas, like the Midwest USA or parts of North Africa.