fossil

Fossilized Coral (Rugose or Tabulate) or Stromatolite

Phylum Cnidaria / Stromatolithus

Mohs hardness typically 3 to 7 depending on silicification (quartz replacement); colors range from gray, brown, tan, to multi-colored; luster is dull to vitreous if agatized; exhibits distinct internal growth lines, wrinkles, or cellular coral structures.

Identified August 1, 2026More fossil →

Explore Fossilized Coral (Rugose or Tabulate) or Stromatolite in the encyclopedia →

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Physical properties

Formation & geological history

Formed in ancient shallow marine environments through the accumulation of calcium carbonate skeletons of colonial marine organisms or microbial mats, subsequently fossilized and often replaced by silica over millions of years (Paleozoic era, e.g., Ordovician to Carboniferous).

Uses & applications

Used as a decorative lapidary stone, in jewelry, and as a prized specimen for fossil and rock collectors.

Geological facts

Many fossil corals found in North America and Europe date back over 300 to 450 million years when continents were covered by shallow warm seas.

Field identification & locations

Identified by distinct concentric bands, wrinkles, or coral calices (tubes/cells) on weathered surfaces. Found in sedimentary limestone or gravel beds worldwide.

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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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