Agatized (Fossil) Coral

  • Agatized (Fossil) Coral
  • Agatized (Fossil) Coral
  • Agatized (Fossil) Coral
  • Agatized (Fossil) Coral
  • Agatized (Fossil) Coral

Agatized Coral forms when silica replaces the original calcium carbonate skeleton of a coral colony. This replacement process creates beautiful specimens with cave-like appearances.


Agatized Coral by Roger Portell

This is an example of Florida’s state stone, which are the fossilized remains of colonial corals which became colorful geodes lined with smooth spherical-shaped agate. The transformation occurs over time when the coral’s original calcium carbonate skeleton is slowly dissolved by acidic groundwater and partially replaced by dissolved silica. The various colors are due to deposition of trace minerals (like iron and manganese) during this process.

This magnificent specimen is part of a collection that was generously donated to the Florida Museum in 2008 by Gene Hamm and his family of High Springs, Florida. For over 40 years Mr. Hamm, his wife and children regularly explored sites along the Suwannee and Withlacoochee rivers looking for these rare 20- to 34-million-year-old specimens.

Roger Portell
Collection Manager, Invertebrate Paleontology
Florida Museum of Natural History


Agatized (Fossil) Coral (Siderastrea sp.)
From Florida
Lived ~34–28 million years ago (Early Oligocene)

State Stone

Exhibit Area

100 Years of History


Sunshine State Symbols

Additional Information

Agatized (Fossil) CoralRadha Krueger