Open Cut » Geology
The objective of this project was to create a public spectral library for coal samples, which did not previously exist. To achieve this, coal samples were scanned using commercially available hyperspectral systems in the Visible Near InfraRed (VNIR) from 450 nm to 1000 nm wavelength, Short-Wave InfraRed (SWIR) from 1000 nm to 2500 nm, Mid-Wave InfraRed (MWIR) from 2500 nm to 7000 nm and Long-Wave InfraRed (LWIR) from 7000 nm to 14000 nm wavelength, including, respectively, Corescan© HCI-3, Agilent 4300 Handheld FTIR and CSIRO HyLogger-3™. The MWIR comprises the fundamental molecular vibrations of the coal, such as stretch and bending, displaying the most intense absorptions compared to the combinations and overtones of those in the VNIR/SWIR which are weaker in intensity.
For this study 18 coal samples were made available by different coal mining companies. The rank of the samples varied from sub-bituminous (0.45% Rr) to low volatile bituminous coal (1.76% Rr); that allowed us to track the evolution of the spectrum during coalification. The results showed that the coal spectrum changes with coalification.
Spectral maps of mineral matter and coal lithotypes were created based on the mineral and coal spectral features, respectively, in the VNIR/SWIR region.
Full spectrum for 14 coal samples can now be incorporated into spectral libraries available for use by anyone. Different types of surfaces were scanned, including slabbed surfaces, outer core, compressed pellets from whole coal and bright bands concentrates, resulting in 46 spectra in the range of 450 nm to 14500 nm. One of the major outcomes of this project is the understanding of the spectral information acquired from coal scanning, how it varies during coalification and which spectral parameters work best for coal characterisation.