gems, spectroscopy, advanced instrumentation, garnet, infrared spectroscopy

Optical spectra are concerned with the quantitative measurement of the absorption, reflection, and emission of light in the near-ultraviolet (∼250 nm) through the mid-infrared (∼3000 nm) portions of the spectrum. The reflection spectroscopy of minerals has been motivated largely by interest in remote sensing. Studies of metal ion site occupancy, oxidation states, and concentrations have generally been done with absorption spectroscopy. This chapter will concentrate on single-crystal absorption spectroscopy.