EPR and optical absorption spectroscopy on minerals

Abstract

In solid state spectroscopy, the study of natural minerals and their synthetic analogues grown in the laboratory plays an important role. In the last three decades a number of investigations have been carried out in this direction using primarily electron paramagnetic resonance (EPR) and optical absorption spectroscopy as tools. An attempt at the systematic presentation of the results has been made in the present paper. Geo-chemically, Mn2+ and Fe3+ occur in many major mineral groups. Estimating the exact percentage of these impurity ions in minerals is useful to grade the minerals for industrial applications. EPR technique is quite useful to assess these impurities even if they are present as minor impurities/traces. EPR technique is also quite effective in the understanding of the properties of these minerals. Other ions Cr3+, Co2+, Ni2+, Cu2+ and Ti3+ are also present as minor impurities though in restricted groups of minerals. These ions are also used as EPR probes. Optical absorption studies of many minerals have been carried out in our laboratories and EPR investigations of suitable minerals have also been undertaken. The optical and EPR results have been correlated to understand the nature of the transition metal environment and bonding characteristics.