Spectroscopic Properties of Rocks and Minerals

Abstract

The fundamental properties that determine spectroscopic behavior of a solid in absorption, reflection, or emission are the optical constants, namely the refractive index and extinction coefficient. For solids, radiation is absorbed or emitted as a consequence of changes in the total energy content of the material. The mafic accessory minerals of intermediate rocks offer the potential for spectral features due to the presence of ferrous and ferric ions, but the best displayed bands are the water and hydroxyl features of alteration products. For geologic materials, electronic processes provide information about the presence and nature of a particular ion and its environment, about adjacent ions, or about defects in specific crystal locations. In the infrared, large variations occur in the value of the extinction coefficient, for solid materials, and it reaches very high values in the region of the resonance frequencies, particularly for silicates near 10 and 20 µm.