The Fort Johnston “rocks” that you see here are not rocks at all. They are what remains of the original fort, constructed using a man made material known as tapia. Tapia is made by mixing a concrete like slurry of crushed oyster shells, sand and lime all of which are still in abundant supply in this area. For more about Fort Johnston, visit the Southport Visitors Center or take a tour with Blue Tarp Tours. And don’t forget…..” Keep On Tourin’ ” y’all.