fossil

Fossil Coral

Rugosa or Tabulata coral fossil (Calcite/Silica replacement)

Hardness varies around 3 to 4 on the Mohs scale for calcified specimens, or up to 7 if silicified. Colors range from white, grey, brown, to yellowish. Luster is dull to vitreous. Crystal structure is hexagonal/trigonal for the replacing calcite or microcrystalline for quartz.

Identified August 3, 2026More fossil →

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Physical properties

Formation & geological history

Formed in ancient shallow marine environments where coral reefs grew, died, and were subsequently buried by sediment. Over millions of years, the original skeletal material (aragonite) was replaced by minerals like calcite, silica, or agate through permineralization.

Uses & applications

Used in lapidary arts, cabochons for jewelry, decorative display pieces, and as a valuable specimen for fossil collectors and geologists studying ancient marine ecosystems.

Geological facts

Fossil corals can date back hundreds of millions of years, often to the Paleozoic era (such as the Devonian and Carboniferous periods). They provide crucial clues about past climates and ancient sea levels.

Field identification & locations

Can be identified by the characteristic honeycomb, star-like, or cellular patterns visible on the surface representing individual coral polyps. Commonly found in sedimentary rock formations worldwide, particularly in limestone-rich areas.

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Crinoid Stem Fossil in Matrix

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Sedimentary Outcrop (Sandstone/Shale)

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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