fossil

Fossilized Coral (Rugose or Tabulate Coral)

Phylum Cnidaria, Class Anthozoa (silicified or calcified coral fossil)

Hardness: 7 on Mohs scale (if silicified/replaced by quartz/chert) or 3-4 (if calcite/limestone); Color: White, grey, brownish tan; Luster: Vitreous to dull; Crystal Structure: Microcrystalline quartz or trigonal calcite with distinct radial or honeycomb corallite structures; Cleavage: None distinct.

Color: White, grey, brownish tan
Luster: Vitreous to dull

Identified August 3, 2026More fossil →

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Physical properties

Formation & geological history

Formed in ancient shallow marine environments, primarily during the Paleozoic era (such as the Devonian or Ordovician periods, roughly 300 to 400 million years ago), where coral skeletons were gradually replaced by silica (chert/flint) or calcite through permineralization.

Uses & applications

Used primarily as educational specimens, in fossil collecting, lapidary arts (cutting and polishing into cabs), and as decorative display pieces.

Geological facts

Fossil corals like this often showcase preservation where the original calcium carbonate structure has been replaced by microcrystalline quartz (chalcedony/chert), making them extremely durable and resistant to weathering.

Field identification & locations

Can be identified in the field by looking for distinct honeycomb, star-like, or radiating tube patterns (corallites) on the weathered surface. Commonly found in limestone and chert-rich gravel beds globally, especially in regions with ancient shallow sea bedrock.

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Microcrystalline Quartz (SiO2) with Calcitic Brachiopod inclusion

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Fossilized Crinoid Stem in Limestone

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Fossiliferous Limestone with Crinoid stems

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