Electronic Spectra of Minerals in the Visible and Near-Infrared Regions

Many of the spectral features ofminerals in the visible to near-infrared region (VNIR; defined here as ~0.4–2.5 μm) arise from electronic transitions within and between transition elements and the anions chemically bound to them. Thousands of minerals have color or wavelengthvariable properties in this portion of the spectrum.Metal ions including vanadium, chromium, manganese, iron, cobalt, nickel, and copper, usually in either the 2+ or 3+ oxidation state, are responsible for the color of many minerals. However, only a few of these elements, typically iron, titanium, and oxygen, are important in most remote sensing applications of rocky bodies. Many features arise from electronic transitions of electrons between the d orbitals of a metal ion, while some spectroscopic features arise from interactions between atoms.