State geologists Harley Means and Tom Scott visited the Miami Circle in 1999. They note that the surface of the limestone at the site is coated with a thin layer of laminated duricrust. This crust is the result of a chemical process that acts on the limestone while it is buried under soil. Earlier research on similar crusts in the Florida Keys indicates that duricrust builds up at about 1mm per 1000 years. This geological evidence confirms the antiquity of the Miami Circle and other carved features at the Brickell Point site.