Spectroscopic and rock magnetic studies on some ancient Indian pottery samples

Abstract

In this study, the ancient potteries from Tamilnadu (Nedungur: Lat.10° 57′N; Long.77°51′E) were collected and investigated for their chemical and mineralogical characteristics to estimate their firing temperature and firing atmosphere. The physical and chemical state of iron (Fe2+/Fe3+) and iron oxide phases obtained using Mössbauer spectra were used to establish the temperature and atmosphere of firing. The clay mineral type and its structural deformation due to firing were established using X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF) and Fourier Transform Infrared (FTIR) Spectroscopy. The data collected from these techniques show that quartz was the predominant mineral, followed by traces of albite, orthoclase and Fe-bearing minerals (hematite and magnetite) and suggested that the firing temperature of potteries lies in the range of 600–800 °C in oxidizing atmosphere. The mineral types and domain states of the constituent magnetic fine particles were elucidated using the variation of susceptibility at various frequencies and temperature under low field. An attempt has also been made to correlate the magnetic parameters from the percentage of Fe2+/Fe3+ and iron oxides. The information obtained paves a way for a better understanding of the technological development that took place in the ancient past and also the suitability of the samples for the determination of reliable ancient geomagnetic field intensity values.