sedimentary
Coral Fossil (Petrified Coral)
Scleractinia (Order) - Calcified Fossil Skeleton (CaCO3)
Hardness: 3.5–4.0 (Mohs scale); Color: White, grey, or tan; Luster: Dull to earthy; Structure: Hexagonal or radiating patterns (corallites); Specific Gravity: 2.6–2.7
- Hardness
- 3
- Color
- White, grey, or tan
- Luster
- Dull to earthy
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Physical properties
Hardness: 3.5–4.0 (Mohs scale); Color: White, grey, or tan; Luster: Dull to earthy; Structure: Hexagonal or radiating patterns (corallites); Specific Gravity: 2.6–2.7
Formation & geological history
Formed through the fossilization of marine coral. As the organic material decays, calcium carbonate minerals (aragonite or calcite) replace or consolidate the skeletal structure in shallow marine environments. Ages can range from recent (Holocene) to hundreds of millions of years old.
Uses & applications
Used primarily for aquarium decor, jewelry (when agatized), landscaping, and as a popular collector's item for hobbyist paleontology.
Geological facts
Many of these specimens found on beaches are relatively young 'calcareous fossils.' If replaced by silica over millions of years, they become 'Agatized Coral,' which is the official state rock of Florida.
Field identification & locations
Identify by looking for the distinct 'star-burst' or honeycomb-like holes (calyx) where the polyps once lived. Commonly found on beaches in Florida, Indonesia, and ancient seabed deposits globally.
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