X-ray Fluorescence and Neutron Activation Analysis of Obsidian from the Red Sea Coast of Eritrea — illustration 1, PDF page 4

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Fig. 2. Selected artifacts from Misse East: Backed blades and geometric tools The XRF analyses were conducted at 35 kV using a tube current of 45 microamps and an operating time of 400 seconds. Concentrations were calculated in parts per million by the ElvaX Regression program based on use of a quadratic regression model for a series of obsidian reference samples previously characterized by both XRF and NAA. The XRF analysis permits quantification of the following elements in obsidian: K, Ti, Mn, Fe, Zn, Ga, Rb, Sr, Y, Zr, and Nb. After completing the analysis by XRF, a subset of the artifacts and the three Kusrale Basin samples were analyzed by NAA to obtain higher resolution data. Due to the destructive nature of sample preparation by NAA, only twenty artifacts were available for analysis. The procedures employed were described in Glascock et al (1999).

Fig. 3. Bivariate plot of Fe and Rb showing the XRF data obtained for three Kusrale Basin source samples and 93 obsidian artifacts from three sites along the Red Sea Coast of Eritrea. Note that Fe can be converted from ppm to percent by dividing by 10,000