THE CHARACTERISTICS AND SIGNIFICANCE OF RUSTICLES FROM THE H. L. HUNLEY

The H. L. Hunley, the world's first successful submarine which sank in 1864 offshore of Carleston, South Carolina, contains a number of rusticles identified on the interior of the hull during excavation. Rusticles are biologically mediated iron concretions that form on exposed iron in marine environments; within the Hunley they are generally one-half to two centimeters in diameter, two to six centimeters in length, and extend down from hull pertubations such as rivet heads, plate seams, and other metal objects. Petrographic observations made with fabricated polished thin sections in both normal and reflected light provide insights on the internal morphology of several rusticles in this preliminary investigation. Different internal regions of the rusticles were found to have different morphologic and chemical character. Chemical assays from SEM/EDS were used to characterize and map the elemental distributions in the rusticles. Different regions, as segregated by their morphology, were found to have different elemental concentrations. It was found that the elemental assemblage from the rusticles as observed in SEM/EDS included; O, Fe, C, Si, Zn, Ca, Cl, S, Mg, Al, Mn, Ti, K, and P. These chemical assays allow for comparison between rusticles collected and studied from other marine wrecks. XRD techniques have also been used to attempt characterization of the specific mineralogy of the generally amorphous samples. These rusticles may provide useful information as to the nature of their formation through time and the environment in which they formed.