The Key Largo limestone is a Pleistocene, white to light gray marine limestone, which contains numerous fossil corals. Some of these corals have been partially dissolved by ground water and the spaces remaining filled with crystalline calcite. The Key Largo limestone is found at the land surface in the Florida Keys from Sand Key to Loggerhead Key. An excellent exposure may be fiewed at Windley Key Fossil Reef Geological State Park, at mile marker 85.5 in the keys