W0142

X-ray Powder Diffraction of Small Amounts of Material (μXRPD): Applications in Archeology. Joseph H. Reibenspies & Nattamai Bhuvanesh, Dept. of Chemistry, Texas A&M Univ., College Station, Texas 77842.

Micro X-ray Powder Diffraction (μXRPD) has been employed in physics, chemistry, forensic sciences, toxicology, geology, art and archeology, just to name a few. There is particular interest in archeological investigations, due to the very small and precious amounts of material. For example, the identification of materials used in the construction of pictographs and ancient wall paintings can help to identify and characterize these items. Materials such as clay, plaster, cement and rock are common substrates on which these paintings are found. For cave paintings the substrates of calcite (CaCO₃) and gypsum (CaSO₄•2H₂O) are of particular interest. These compounds can identify the type of cave environment where the paintings were originally drawn. Unfortunately the amount of material in archeological investigations is very small (sometimes only a few grains) and methods must be developed to identify even micro amounts of material. Our laboratory has developed new methods for μXRPD based upon pinhole X-ray sources and area detectors (CCD and Multi-wire). Powder mounts including single-crystals, nylon loops and Mylar^® film have been employed to analyze micro-grams of material. This presentation will discuss these methods and show examples of μXRPD for calcite and gypsum.