fossil

Fossilized Coral

Rugose Coral / Hexagonaria (Fossilized calcium carbonate)

Hardness: 3-4 on the Mohs scale (for calcite/aragonite replacement), Color: Varies from white, grey, beige to brown, Luster: Dull to vitreous, Crystal structure: Trigonal (mineralized as calcite)

Identified July 30, 2026More fossil →

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Physical properties

Hardness: 3-4 on the Mohs scale (for calcite/aragonite replacement), Color: Varies from white, grey, beige to brown, Luster: Dull to vitreous, Crystal structure: Trigonal (mineralized as calcite)

Formation & geological history

Formed when ancient marine coral skeletons were buried in sediment and gradually replaced by minerals like silica or calcite over millions of years, often dating from the Paleozoic era (such as the Devonian or Carboniferous periods)

Uses & applications

Used as a decorative lapidary stone, in jewelry making, education, and as a collectible geological specimen

Geological facts

Many fossilized corals, such as Petoskey stones, are state stones and provide crucial evidence of ancient tropical shallow seas in regions that are now temperate or dry land

Field identification & locations

Easily identified by distinctive honeycomb or star-like corallite patterns on the surface; commonly found in limestone-rich sedimentary rock formations worldwide

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