National Park Service U.S. Department of the Interior

Fort Matanzas Fort Matanzas National Monument

Coquina - The that Saved St. Augustine

A Fort Made out of Who would think that a fort made of ? seashells would last 300 years? Who would think that a fort made out of seashells would last three days under cannon fire?

But the , made of local coquina stone, did and has survived very well for over 300 years. What exactly is this strange rock? How was it formed, and where did it come from? And how did this rock shape the history of St. Augustine?

How Coquina is Thousands of years ago, the tiny coquina water percolating through the dead Formed clam donax variabilis lived in the shallow vegetation and soil picked up carbon waters of coastal , as they still do dioxide and became carbonic acid, the today. These are the small pink, lavender, same ingredient that makes soda pop fizz.

yellow, or white shells one sees along the beach at the waterline. As the resident As this weak acid soaked downward, it clam died, the shells accumulated in layers, dissolved some of the calcium in the shells, year after year, century after century, for producing calcium carbonate, which thousands of years forming submerged solidified in lower layers much like deposits several feet thick. flowstone and stalactites are formed in caves. This material "glued" the shell During the last ice age, sea levels dropped, fragments together into a porous type of exposing these shell layers to air and rain. we now call coquina, Spanish Eventually, the shell became covered with for "tiny shell". soil, then trees and other vegetation. Rain

A Stronger Fort Although found in very few places in the British from taking over Florida and using Is Needed world, conditions were just right that it as a base of operations to attack the several deposits of this shell rock formed Spanish treasure fleets and the more along the east coast of Florida. The wealthy colonies of the Spanish Spanish knew about this rock, and while Caribbean. they might have picked up loose chunks, the people of St. Augustine were primarily So, in 1672, the Spanish began to build the soldiers, not stone masons, and so this Castillo de San Marcos out of coquina rock sat mostly unused and unappreciated stone from a quarry located in the area of for years. Wood was more plentiful, at present-day Anastasia State Recreation first, and easier to work with. Area on . Military engineers and stone masons were brought But then the British, settling to the north, from Spain. Convicts and additional edged into the Carolinas. Spanish Florida soldiers were brought from Cuba. Oyster was only a short sail away. Something shells were burned into lime, mixed with more than a wooden fort was needed to sand and water to make mortar. protect St. Augustine and to keep the

Attack! Slowly the walls rose. Since no one had Moore from Charleston led his British ever built a fort or any large building out of forces against St. Augustine and the Castillo. coquina, they had no idea how strong it He captured the town and set his cannon up would be. At least it would not burn, and among the houses to bombard the fortress. the termites wouldn’t eat it. But how well But a strange thing happened. Instead of would seashells last under cannon fire? No shattering, the coquina stone merely one knew, so they built the walls 12 feet compressed and absorbed the shock of the (3.7m) thick with the walls on the ocean side hit! The cannon balls just bounced off or 19 feet (5.8 m) thick! stuck in a few inches! The shell rock worked! (It is not true that the cannonballs They did not have long to wait before the were then dug out of the walls and shot back coquina walls were tested. In 1702 James at the enemy.

The Rock that Even when General Oglethorpe tried his and not much clay, either, to make bricks. If Changed History? hand against Srt. Augustine in 1740 and not for coquina, perhaps the British would bombarded the Castillo for 27 days, the have captured St. Augustine much earlier walls held firm. The rock made of seashells than 1763 when they finally gained Florida turned out to be an excellent building by treaty. If the British had Florida earlier, it material. When the Spanish decided to might have changed the course of the fortify the southern approaches to St. American Revolution. Maybe our country Augustine by building Fort Matanzas later would still be a part of Great Britain as a that year, they again used coquina stone, commonwealth like Canada! and like the Castillo, this smaller fort was never captured, either. Our history might have been quite different but for this little clam known as donax and This makes one think. What if the Spanish for coquina, the rock that saved St. had not had this coquina stone? Afterall, Augustine. there is not a lot of exposed rock in Florida LAC 1999 LAC 1999

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