Agatized Coral - Florida's State Stone

There's a reason why we call our award-winning monthly newsletter The Coral Geode.

In 1979, the Florida State Legislature passed a bill designating agatized coral (coral geode) as the State Stone of Florida, and some of the finest examples of this fossilized material are found in the Tampa Bay area.

Agatized coral, in many forms and colors, is found all over Florida. Sometimes these heads are solid; some, as around Tampa Bay, are hollow and properly called "geodes." Agatized coral is scientifically identified as "Chalcedony Pseudomorph after Coral" because one mineral (the limestone of the coral) has been replaced with another (a form of quartz called chalcedony).

Millions of years ago these "rocks" were colonies of little undersea animals; they grew as polyps. Coral is the name of the limey skeletons with which they encased themselves. Diluvial action over the ages covered these colonies of animals in water which contained other minerals. Over a long period of time, the carbonate of lime skeleton was replaced by the form chalcedony.

The geodes found in the Tampa Bay area may have hollow centers colored red, blue or black, or  varying sizes of quartz crystals. In the northern part of Florida, solid heads of various shades of yellows, banded with blue or black, have been found. Beautiful specimens have been found on the Caladesi Causeway. Other beautiful specimens have been located in the Perry area -- Econfina and Buckeye.

The crystal heads of northern Florida differ from the Tampa Bay heads. While heads have been found in all areas, no fingers have been found in the northern Suwannee basin. Many enhydros are found (these still have water trapped in them from ancient eras); while they are sometimes in salt water, the water contained in them is always fresh.

Heads and "fingers" (individual coral branches) are highly priced as specimens, cut into symmetrical halves and polished. Smaller pieces are made into jewelry. They have come to be known as "Ballast Point Diamonds" because they were first found in quantity at Ballast Point in Tampa, Florida, and to coral lovers, their beauty rivals that of the diamond.