fossil

Polished fossil coral

Fossilized coral, commonly agatized coral (silica replacing CaCO₃)

AI-generated identification · may be incorrect

Typically Mohs 6.5–7 when silicified; tan, honey, orange, or brown with distinctive polygonal coral-cell patterns, vitreous to waxy luster, and no obvious cleavage. The visible honeycomb texture strongly indicates coral structure rather than ordinary jasper.

Identified August 29, 2026More fossil →

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Physical properties

Formation & geological history

Ancient coral colonies were buried in marine sediments and mineralized as silica or chalcedony replaced the original skeleton, often during the Paleozoic–Cenozoic eras. Common sources include Indonesia, Madagascar, Florida, and the western United States.

Uses & applications

Used as a polished ornamental stone, cabochons, beads, carvings, and jewelry; it has little industrial value. Collecting value depends on pattern quality, polish, size, and confirmed provenance.

Geological facts

Agatized coral preserves individual corallite chambers, producing the characteristic web-like or honeycomb pattern. It is a fossil rather than a true igneous, sedimentary, or metamorphic rock.

Field identification & locations

Identify it by repeating polygonal cells across the surface, silica-like hardness, and inability to scratch with a steel nail; acid testing should be avoided or done cautiously. Common polished pieces sell for about $10–$50, while large, exceptionally patterned specimens may reach $100–$300.