sedimentary
Fossil Coral
Scleractinia (Anthos), primarily Calcium Carbonate (CaCO3)
Hardness: 3.5 to 4.0; Color: White, cream, or pale beige; Luster: Dull to earthy; Texture: Porous with visible radial septal structures (corallites); Cleavage: None
- Hardness
- 3
- Color
- White, cream, or pale beige
- Luster
- Dull to earthy
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 3.5 to 4.0; Color: White, cream, or pale beige; Luster: Dull to earthy; Texture: Porous with visible radial septal structures (corallites); Cleavage: None
Formation & geological history
Formed by the accumulation of calcium carbonate skeletons from marine polyps. Over millions of years, these remains are buried under sediment and lithified into rock. Most specimens range from the Devonian period to recent Holocene formations.
Uses & applications
Used primarily in home decor, jewelry (when agatized), construction materials (limestone), and as a teaching tool for paleontology.
Geological facts
Fossil corals are direct evidence of ancient warm, shallow seas. While many are found as limestone, 'Agatized Coral' occurs when the original calcium carbonate is replaced by silica, turning it into a semi-precious gemstone over 20-30 million years.
Field identification & locations
Identify in the field by looking for distinct radial, star-like, or honeycomb patterns on the surface of white/grey rocks. Common in limestone quarries or coastal areas like Florida, Indonesia, and Morocco.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary