Tracing the use of freshwater naiad shells as prehistoric implements through scanning electron microscopy and x-ray microanalysis

Abstract

Many freshwater naiad shells recovered from prehistoric Iowa archaeological sites have edges exhibiting patterns of use-wear. The ethnographic and ethnohistoric records contain accounts of the use of these shells in the removal of kernels from corn cobs. Recently, archaeologists have begun tracing use of stone implements through analysis of microscopic wear patterns and deposition of material such as opal phytoliths. Opal phytoliths are small silica bodies which plants deposit within and between some cells. Corn is among the plants which produce opal phytoliths in abundance. Experimentally created naiad shell implements were used to remove kernels from corn cobs. The deposits left on the edges of these implements were compared to those of prehistoric naiad shells thought to be utilized. Scanning electron microscopy (SEM) and x-ray microanalysis were utilized.The prehistoric and experimentally created edges were prepared for examination by cleaning and coating with carbon. Examination of the tools was performed with a Hitachi S-570 electron microscope equipped with a Kevex 8000 x-ray microanalyzer.