MIR spectral library

Reflectance spectra collected of rocks and soils in the mid infrared wavelength range (2500 to 6000 nm; MIR) of the electromagnetic spectrum contain fingerprints of a wide range of rock forming and alteration minerals. The MIR is complementary to the visible-near infrared (VNIR; 380 to 1300 nm), shortwave infrared (SWIR; 1300 to 2500 nm), and thermal infrared (TIR; 6000 to 15000 nm) wavelength ranges. However, due to technological challenges with regards to proximal and remote hyperspectral sensing instruments, the MIR has been underutilised with regards to applications in mineral exploration and mining. With the advent of readily commercially available, hyperspectral handheld and drill core sensing instruments, such as portable Fourier transform infrared (pFTIR) spectrometers and the newly developed HyLogger4TM (Corescan Pty Ltd.), reflectance spectra of this relatively unexplored wavelength range become accessible to the mineral resources sector. Numerous methods exist for inferring mineralogy from hyperspectral reflectance spectra collected from, for example, drill core or field samples, ranging from automated or semi-automated unmixing algorithms that compare the collected reflectance spectra with a spectral reference library (e.g. https://mineralspectrallibraries.csiro.au/) to scripts targeting specific mineral groups and Gaussian deconvolution. This collection of MIR reflectance spectra aims to help improve the understanding of MIR spectral signatures of rock forming and vector minerals that will underpin the development and testing of methods for inferring, for example, relative mineral abundance, mineral composition, crystallinity, water content and grain size from the MIR wavelength range. The presented MIR reflectance spectra feature associated quantitative and semi-quantitative X-ray diffractometry, measured from various types of samples that were collected from a wide range of geological environments.