Rock Identifier
Fossiliferous limestone with colonial coral (Calcite (CaCO₃) limestone containing fossil tabulate or rugose coral colonies) — fossil
fossil

Fossiliferous limestone with colonial coral

Calcite (CaCO₃) limestone containing fossil tabulate or rugose coral colonies

AI-generated identification · may be incorrect

Typically cream to tan and earthy, with abundant polygonal coral corallites; calcite has Mohs hardness 3, vitreous to dull luster, rhombohedral cleavage, and specific gravity about 2.7. It effervesces strongly with dilute hydrochloric acid.

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Physical properties

Typically cream to tan and earthy, with abundant polygonal coral corallites; calcite has Mohs hardness 3, vitreous to dull luster, rhombohedral cleavage, and specific gravity about 2.7. It effervesces strongly with dilute hydrochloric acid.

Formation & geological history

A marine carbonate sediment accumulated and lithified around Paleozoic coral colonies, commonly Devonian to Permian in age (about 419–252 million years old). Burial, compaction, and calcite cement produced the limestone matrix.

Uses & applications

Used mainly as a collectible fossil specimen, educational material, and decorative stone; related limestone is widely used for cement, aggregate, and building stone. Value depends on preservation, rarity, and preparation quality.

Geological facts

The repeated cup- or honeycomb-like structures are individual coral corallites, not mineral crystals. Coral fossils can indicate warm, shallow, well-oxygenated ancient seas.

Field identification & locations

Identify it by the regular corallite pattern and acid reaction of the matrix; common localities include the Great Lakes region, Morocco, Australia, and parts of Europe. Avoid confusing it with man-made coral-textured concrete or modern coral.

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