fossil

Petrified Coral Fossil (Honeycomb Coral)

Favosites (Rugosa/Tabulate coral fossil replaced by microcrystalline quartz/chalcedony)

Hardness: 6.5-7 on the Mohs scale (due to silification); Color: Tan, brown, or grayish-white; Luster: Vitreous to waxy; Crystal structure: Trigonal (cryptocrystalline quartz); Cleavage: None

Hardness: 6
Color: Tan, brown, or grayish-white
Luster: Vitreous to waxy

Identified August 3, 2026More fossil →

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Physical properties

Hardness: 6.5-7 on the Mohs scale (due to silification); Color: Tan, brown, or grayish-white; Luster: Vitreous to waxy; Crystal structure: Trigonal (cryptocrystalline quartz); Cleavage: None

Formation & geological history

Formed when ancient coral skeletons from the Paleozoic era (approx. 400 million years ago) were buried in sediment and gradually replaced mineral by mineral with silica-rich groundwater over millions of years.

Uses & applications

Used primarily in lapidary work, wire-wrapped jewelry, decorative display pieces, and as a prized specimen for fossil and rock collectors.

Geological facts

Favosites is commonly known as 'honeycomb coral' due to the distinctive polygonal, tightly packed corallites that resemble a bee's honeycomb.

Field identification & locations

Easily identified in the field by its distinct geometric honeycomb-like pattern of tubes or cells on the surface. Commonly found in ancient marine limestone deposits, particularly in regions like Michigan, USA, and worldwide where shallow Paleozoic seas once existed.

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