Combined Thermal and X-Ray Diffraction Technique for Identification of Ceramicware Temper and Paste Minerals

AbstractThe identification of the original paste and temper minerals present in ceramicware fragments can often be useful in determining if the fragments are indigenous to the area or whether they represent tradeware. To date, it has generally been believed that no certain means existed to identify the mineral constitutents once they were destroyed in the original kiln-firing operation. A new technique is described that permits the investigator to often identify both temper and the fine-grained paste materials as well. This method involves: (1) crushing the fragment to a fine powder; (2) heating the powder in a high temperature furnace to sufficient temperatures to cause the constituent ions present to recombine to form new, high temperature minerals; and (3) X-ray diffraction analysis to identify the new minerals. In many cases, identification of the resulting high temperature minerals will clearly indicate the composition of the original clay paste and temper. Examples are shown for the clay minerals kaolinite, montmorillonite and palygorskite. Diffractograms are also presented for comparison of ceramic fragments from Mexico and Alabama that contain the above minerals as original constituents.