Standoff mid-infrared reflectance spectroscopy using quantum cascade laser for mineral identification

In this work, quantum cascade laser (QCL) mid-infrared (MIR) reflectance spectroscopy is used to discriminate silicate and carbonate minerals in a standoff measurement setting. The tunable external cavity QCL source that was used allows measurements from 5.2 μm to 13.4 μm wavelength, where the fundamental vibrational bands of silicates and carbonates are observed. Spectra measured from a half-core sample were analyzed using multivariate analysis to extract and identify the end-member spectra from the mixtures. The end-member spectra were compared and validated using the ASTER database spectra and the spectra measured on reference samples with the same QCL MIR reflectance spectroscopy setup. Spectra of minerals commonly found in the mining industry were compared: quartz, microcline, albite, chlorite, muscovite, biotite, calcite and dolomite. MIR reflectance spectroscopy using compact QCL sources allow rapid spectral measurements at standoff distances and high spatial resolution. All these advantages show the potential of QCL MIR reflectance spectroscopy for in-the-field mining applications.