Florida’s state stone is agatized coral: ancient coral heads whose structure was replaced over millions of years, cell by cell, with agate and chalcedony, so a fossil coral turns to a gemstone that takes a polish. It weathers out of the Tampa Bay country and the Withlacoochee and Suwannee riverbeds; the Ballast Point and Tampa Bay area is the classic ground. Check land and collecting rules before you dig a bank.
Agatized coral
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Other places on the map within a couple of hours.