A Trial PIXE/PIGME analysis of Pre-Islamic Arabian Coinage

Eight previously published (1) pre-Islamic coins minted in Arabia were subjected to non-destructive ion beam analysis by Proton Induced X-Ray (PIXE) and Gamma-Ray Emission (PIGME) at Lucas Heights. The results (2) were interpreted using Principal Components Analysis (PCA). The relative X-ray intensities of fifteen elements, supplemented with additional L alpha lines for two of the elements, were extracted for this analysis. PCA (results appended) was first carried out on the whole dataset where the distinctive high iron and nickel composition of two coins (331 and 335) resulted in their position as outliers. A second analysis of the subset of silver coins showed the compositional similarity between four coins (44, 222, 226, 359) and distinguished two separate outliers. One of these (369) has a high lead and tin content while the other (354) has a greater proportion of elements present as impurities (?) including iron and nickel. The two outliers and the relatively homogenous compositions of the group of four coins suggest that three compositional types of silver coinage are represented in the dataset: 1. a relatively silver-rich group of four coins; 2. silver coins debased with lead; and 3. silver coins debased with iron and nickel.