NON-DESTRUCTIVE GEOCHEMICAL ANALYSIS OF TOOL STONE QUARRY MATERIAL FROM WEST TEXAS

Five flake samples from each of four tool stone sources from the Big Bend region of west Texas (one chert, two brown agates, one rhyolite) were analyzed using non-destructive Energy Dispersive Spectroscopy (EDS) associated with a Scanning Electron Microscope (SEM). The twenty flakes were made for this study by breaking them from known tool stone sources. The flakes were no longer than 50 mm and no thicker than 15 mm in order to fit inside the SEM chamber for analysis. The procedure was to get a chemical analysis (spectrum and element maps) of two small areas per flake, one at each extremity. Then a grid was superimposed on the flake and a point analysis taken within each cell of the grid. There were no less than thirty point analyses per flake. The two area maps on each flake were compared and then the maps of all five flakes of the same rock type were compared. Preliminary results indicate that the chert may have a unique chemical signature indicated by the presence of Al and Ca. The brown agates were from two different areas and preliminary results suggest that each brown agate may have a unique chemical signature. One agate contained abundant Fe and common Al, K, and Ca. The other agate contained higher abundances of these elements as well as Mg, Mn and Ti. The rhyolite was chemically heterogeneous and preliminary results indicate no unique chemical pattern in the map areas. Preliminary results of the point analyses of the tool stone samples do not indicate any discernible unique chemical signature. This EDS chemical map methodology needs to be tested further. This method is currently being applied to archeological artifacts.