Coral Fossil (Petrified Coral)

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.

Identified on: 4/17/2026

Mode: Standard