fossil

Fossil coral (likely colonial/tabulate coral)

Fossilized scleractinian or tabulate coral; calcium carbonate, chiefly CaCO₃ (calcite/aragonite replaced by calcite)

AI-generated identification · may be incorrect

Hardness about 3–4 Mohs, pale gray to tan with weathered brown-green patches, dull to slightly waxy luster, and abundant polygonal corallite chambers or honeycomb-like skeletal structure. Cleavage is poor to absent; specific gravity is roughly 2.6–2.8.

Identified August 12, 2026More fossil →

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At a glance

Common name: Fossil coral (likely colonial/tabulate coral)
Scientific name: Fossilized scleractinian or tabulate coral; calcium carbonate, chiefly CaCO₃ (calcite/aragonite replaced by calcite)
Category: fossil
Identified: August 12, 2026
Method: Standard

AI Estimated Value

Approximately $5–$30 for a common weathered piece; $30–$150 or more for large, well-preserved, locality-documented specimens.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

A colonial marine coral skeleton was buried in carbonate sediment and mineralized during diagenesis, commonly during the Paleozoic or Mesozoic; the exact age cannot be determined from the photograph. Weathering has exposed the internal coral structure.

Uses & applications

Primarily a collector specimen, educational fossil, or decorative stone; fossil coral is occasionally polished for jewelry and cabochons, but it is not generally used as structural stone.

Geological facts

The repeated pits and walls represent individual coral polyps, allowing identification as a colonial coral rather than ordinary limestone. Acid may cause weak effervescence if carbonate remains exposed.

Field identification & locations

Common in ancient shallow-marine limestone beds worldwide, including parts of North America, Europe, Australia, and Asia. Confirm by examining the regular corallite pattern and testing a hidden area with dilute hydrochloric acid; avoid damaging valuable specimens.