fossil

Fossil Coral

Rugosa or Tabulata coral fossil (Calcium Carbonate, CaCO3)

Hardness: 3-4 on the Mohs scale; Color: White, grey, brownish, or yellowish; Luster: Dull to vitreous; Crystal Structure: Hexagonal (calcic); Cleavage: Perfect rhombohedral; Specific Gravity: 2.71

Hardness: 3-4 on the Mohs scale
Color: White, grey, brownish, or yellowish
Luster: Dull to vitreous

Identified August 3, 2026More fossil →

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Physical properties

Hardness: 3-4 on the Mohs scale; Color: White, grey, brownish, or yellowish; Luster: Dull to vitreous; Crystal Structure: Hexagonal (calcic); Cleavage: Perfect rhombohedral; Specific Gravity: 2.71

Formation & geological history

Formed through the process of permineralization or silicification, where ancient coral skeletons from prehistoric shallow marine environments (dating from the Paleozoic to Cenozoic eras, hundreds of millions of years ago) are preserved in sedimentary rock formations and later exposed by weathering.

Uses & applications

Used as lapidary material for cabochons and jewelry, as well as valued specimens for fossil and rock collectors.

Geological facts

Fossil corals provide crucial insights into ancient marine ecosystems, paleoclimates, and ancient plate tectonic positions. Many specimens are silicified, meaning the original calcium carbonate has been replaced by microcrystalline quartz.

Field identification & locations

Easily identified by the distinctive honeycomb or star-like patterned pores (corallites) visible on the surface. Commonly found in limestone and sedimentary deposits worldwide, particularly in areas with ancient seabed history.

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Sedimentary bedrock formation (variable composition)

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Chert with Fossil Brachiopod

Microcrystalline Quartz (SiO2) with Calcitic Brachiopod inclusion

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Fossilized Crinoid Stem in Limestone

Crinoidea (Class) in Calcium Carbonate (CaCO3) matrix

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Fossiliferous Limestone

Limestone with embedded fossil cross-section

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Fossiliferous Limestone with Crinoid stems

Limestone (CaCO3) containing Crinoidea fossils

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