PIXE analysis of ancient Indian coins

A number of coins of Hindu Shahis Dynasty of Kabul (990–1015 A.D.) have been analysed using proton induced X-ray emission (PIXE) technique. The 3 MeV proton beam from the Pelletron Accelerator at the Institute of Physics, Bhubaneswar, India was used for the production of X-rays. The X-rays were detected by Si(Li) detector ( FWHM=180 eV at 5.9 keV) placed at 90° to the beam direction. For the reliable calibration of the analytical system, thin foils of Micromatter standards of Fe, CuS, KCl, and RbNO3 were used. The computer code GUPIX was employed to get concentration of trace elements in these coins. The elements Ca, Ti, Cr, Fe, Ni, Zn, As, Sb, Pb, and Bi were detected in these coins alongwith the major component of Cu and Ag. The coins were classified in two groups, coins no. 3, 9, 10, 11, 13, 14, 15, 16, 18, 19 as copper or billon coins having major component of copper, while coins no. 6, 17, 20, 21, 22 as silver coins having the major component of silver. The first group seems to belong to lower denomination while the other group belongs to higher denomination coins. There is a strong positive correlation between lead and zinc and also a strong negative correlation between copper and silver. The weight of coins varied between 3.05 and 3.39 gram. The comparison of our results with that of the ores of various mines indicates that the source of copper in these coins is from Khetri mine in Rajasthan. Silver seems to come from Afghanistan since it is not reported to occur as a primary mineral in ancient India.