Waterfront home in Miami Beach that we supplied the authentic florida keystone tiles. notice the natural patina that occurs over time, now this is what a coral stone pool deck is suppose to look like NICE. The islands of the Lower Keys in the Florida Keys, as well as some barrier islands east of Miami bordering Biscayne Bay, are mainly oolitic limestone, which was formed by deposition when shallow seas covered the area between periods of glaciation. The material consolidated and eroded during later exposure above the ocean surface.