fossil

Fossilized coral fragment

Agatized or silicified coral, likely *Hexagonaria* (identification uncertain from photo)

AI-generated identification · may be incorrect

Gray-beige, fine-grained and dull to slightly waxy; the pale branching/polygonal pattern may represent fossil corallite structures. Hardness is typically about 6.5–7 Mohs if silicified, with no obvious cleavage and moderate-to-high density.

Identified September 6, 2026More fossil →

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Physical properties

Formation & geological history

Ancient colonial coral was buried in marine sediment and later replaced or infilled by silica-rich groundwater, commonly during the Paleozoic (roughly 250–450 million years ago). Weathering exposed the fossil fragment.

Uses & applications

Used as a decorative stone, cabochon material, educational specimen, and collector fossil; silicified coral can be polished for jewelry and ornaments.

Geological facts

Fossil corals often preserve repeated corallite cells or honeycomb patterns, distinguishing them from ordinary veined limestone. Exact species requires a close examination of the corallite geometry and surface.

Field identification & locations

Look for consistent repeated cell patterns across broken or polished surfaces, rather than random mineral veins; common examples occur in Paleozoic marine limestones of the Great Lakes region and elsewhere. A hand lens and acid test can help distinguish limestone matrix from silica replacement.