There is a pair of Fossilized Agatized Coral. One piece measures  approx. 141 x 37 mm: thickness is 19 mm: weight is 145 grams. The other piece measures approx. 94 x 40 mm: thickness 23 mm: weight is 74 grams. The faces of these pairs are polished and there are some great botryoidal's. They were found in Tampa Bay, Florida.
 
Agatized Coral are the skeletal remains of anthozoans. These animals died some 25 to 38 million years ago. Agatized process over time is when the coral and the limestone voids are filled with silica rich water and the limestone is replaced by chalcedony quartz aka a common opal.