fossil
Coral Fossil (Hexagonaria)
Hexagonaria sp. (Silica-replaced)
Hardness: 6.5-7 (if silicified); Color: Tan, beige, or grey with distinctive dark circular/hexagonal pores; Luster: Dull to waxy; Structure: Colonial coral polyps; Cleavage: None.
- Hardness
- 6
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 (if silicified); Color: Tan, beige, or grey with distinctive dark circular/hexagonal pores; Luster: Dull to waxy; Structure: Colonial coral polyps; Cleavage: None.
Formation & geological history
Formed during the Devonian period (approx. 350-400 million years ago) in warm, shallow saltwater seas. The organic coral skeleton was replaced by silica or calcite over millions of years.
Uses & applications
Primarily used for educational purposes, geological collecting, and lapidary work (jewelry and polishing).
Geological facts
This specimen is closely related to the Petoskey Stone, the state rock of Michigan. The distinct pattern is created by the fossilized individual coral polyps known as corallites.
Field identification & locations
Identify by looking for a honeycomb or 'measles' pattern on the surface. Commonly found along the shores of the Great Lakes (especially Lake Michigan) and in limestone quarries in the Midwest U.S.
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