Rock Identifier
Polished fossiliferous coral (agatized coral) (Silicified colonial coral; commonly sold as fossil coral or agatized coral) — fossil
fossil

Polished fossiliferous coral (agatized coral)

Silicified colonial coral; commonly sold as fossil coral or agatized coral

AI-generated identification · may be incorrect

Orange-brown, glossy polished surface with intricate coral-like cell patterns in silica and a rough, pale host matrix. Silica is Mohs 6.5–7, typically microcrystalline; the fossil’s original carbonate may be partly or wholly replaced.

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Physical properties

Orange-brown, glossy polished surface with intricate coral-like cell patterns in silica and a rough, pale host matrix. Silica is Mohs 6.5–7, typically microcrystalline; the fossil’s original carbonate may be partly or wholly replaced.

Formation & geological history

Ancient coral colonies were buried in sediment and later mineralized or replaced by silica-rich groundwater, preserving their skeletal patterns. Fossil ages and host deposits vary widely, commonly spanning Paleozoic to Cenozoic strata.

Uses & applications

Collected and displayed as a fossil specimen; polished pieces are also used for cabochons and decorative objects.

Geological facts

Silicification can preserve fine details of coral corallites, producing patterns that resemble lace or honeycomb.

Field identification & locations

Identify by repeated coral-polyp structures rather than random banding; inspect the polished face with magnification. Fossil coral occurs in sedimentary formations worldwide, including Florida and Indonesia.

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