Question: What is known as the rock that saved St. Augustine?
Answer: Coquina
Although found in very few places in the world, conditions were just right for forming the stone known as coquina along the east coast of Florida. The Spanish began construction on the Castillo de San Marcos in 1672 with coquina stone quarried in the area of present-day Anastasia State Park on Anastasia Island. Coquina doesn’t shatter or crack when hit by cannon fire. Instead, it absorbs the shock. That fact saved the fort from invaders several times.
