sedimentary

Tumbled coral limestone

Biogenic calcarenite/coral limestone, predominantly calcium carbonate (CaCO₃; calcite/aragonite)

AI-generated identification · may be incorrect

Cream-white, fine-grained, dull to satin luster, with abundant rounded fossil pores and cavities; Mohs hardness about 3, no visible cleavage, and typically reacts vigorously with dilute hydrochloric acid or vinegar.

Identified September 4, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from accumulated coral skeletons and other marine carbonate debris, later lithified and naturally or artificially rounded by abrasion. The specimen’s exact geological age cannot be determined visually; coral limestones range from modern to Paleozoic–Cenozoic.

Uses & applications

Used as a decorative or educational specimen, aquarium décor, and occasionally as ornamental stone; it is generally unsuitable for durable jewelry because calcite is soft and porous.

Geological facts

The hole patterns preserve the original coral framework or later dissolution cavities. Aragonitic coral may recrystallize into calcite during diagenesis, obscuring the original structure.

Field identification & locations

Common in tropical reef and raised-reef deposits, including Florida, the Caribbean, the Indo-Pacific, and Mediterranean regions. Identify it by its lightweight porous texture, carbonate acid reaction, and fossil-coral pattern; avoid confusing it with pumice or ceramic.