A study of mid-infrared reflectance spectra of powdered mineral mixtures

Interest is growing in the use of mid-infrared reflectance and emittance spectra for both laboratory and remote sensing applications. Yet much work still needs to be done to better understand the uses of mineral and rock spectra. This study examines high resolution laboratory spectra of powdered mineral samples. The three sections of this work look at the linearity of spectra of mixtures, the mineralogic information in spectral mixtures and a spectral unmixing technique.;A statistical correlation analysis of looks for strong correlations between spectral bands of varying width and mineral type, major oxide content, and polymerization indicators. The strongest and most useful correlations were associated with polymerization indicators and major oxides that are associated with degree of polymerization. Results confirm that mineralogic information is retained at broad band widths.;The least squares technique was employed to unmix the mid-infrared spectra. Using a suit of pure mineral spectra the methods closely predicts the mineral type and percentage in a mixture. The technique promises to be useful in the laboratory as a non-destructive technique for mineral determination, and may have applications for remote sensing as well.;The linear mixing relationship for mid-infrared mineral mixtures is demonstrated for the first time. This contrasts with the non-linear mixing model in the visible and near infrared and in absorption spectra in the mid-infrared. The linear relationship points to the use of spectral unmixing techniques to predict the composition of mixed materials.