The optical absorption spectra of certain transition metal ions in muscovite, lepidolite, and fuchsite

The unpolarized optical absorption spectra of the sheet silicate minerals muscovite, lepidolite, and fuchsite have been examined. The spectra, interpreted on the basis of ligand field theory, indicate that all three minerals contain Fe 3+ and possibly Ti 3+ in octahedral sites. In addition, muscovite is shown to contain octahedrally coordinated Fe 2+ , lepidolite octahedral Fe 2+ and Mn 2+ , and fuchsite octahedral Cr 3+ . No evidence was found for transition metals in tetrahedral sites.Some comments are made on the similarity of the spectra of certain of the transition metal ions in several classes of minerals. This leads to the speculation that the cations Fe3 + , Mn 2+ , and Cr 3+ may tend to 'mold' their immediate surroundings.