Infrared absorption spectra of plagioclase feldspar: Dependencies of composition and temperature

We investigated the absorption spectra of crystalline plagioclase feldspar, using natural and synthetic samples with a wide compositional range, in the infrared region. And we also carried out cryogenic measurements for synthetic anorthite. In the absorption spectra, systematic spectroscopic variations that depend on the chemical composition were observed, in terms of characteristic features such as the number of absorption peaks, shift of peak location and variety of peak width and intensity. Since, plagioclase feldspar is considered as a reasonable mineral species formed in oxygen rich circumstellar environments from the viewpoint of the equilibrium condensation sequence, our spectral data obtained in this work is expected to be used widely in the field of astronomical mineralogy.