The science behind it
Infrared images are captured using an appropriate illumination source reflected off a sample and measured by an imaging spectrometer. Specific bonds present in the sample cause absorptions in the measured reflectance spectra. These spectral signatures then reflect characteristic features that allow mineral identification and mineral variation determination. Minerals are detected in the infrared imagery depending on the bonds present in the sample and the infrared wavelength range measured.
The infrared and mineral detection
The electromagnetic spectrum can be divided into different wavelength ranges. Hydroxyl and carbonate bond related vibrations are typically measured in the shortwave infrared (SWIR). Phyllosilicate and carbonate minerals are commonly identified across the SWIR region. Clay minerals, micas, chlorites and different carbonate species are detectable. The SWIR is an important range for mineral detection. Longer wavelength ranges are necessary to detect the fundamental vibrations related to silica and aluminium. In the longwave infrared (LWIR) region quartz, feldspar and other silicate minerals can be detected and identified. Often referred to as the thermal infrared this region is another important range for mineral detection.