## 5 Discussion and Conclusions  
Utilising a simple combination of two spectral metrics, namely the Fe oxide wavelength and the Fe oxide FWHM, it is demonstrated that a large collection of spectral samples from BIF, BID and CID of the Pilbara Province of Western Australia fall within a distinctive manifold. The manifold named the iron boomerang provides an overview of the dataset and offers a qualitative means of ascertaining the iron oxides paragenesis and when incorporated with other spectral metrics, the possibility to further subclass the goethite types. It was shown that the distribution of the samples when examined in a density plot along the peripheries of the iron boomerang is lower than those within the core of the iron boomerang probably because of the samples mostly occurring in BID. If the dataset contains unmixed hematite and vitreous goethite, then two spectral endmembers can be located at either end of the iron boomerang. Samples comprised of the shortest Fe oxide wavelengths and the smallest Fe oxide FWHM values are comprised of hematite while those at approximately 1050 nm and with an Fe oxide FWHM value greater than 370 nm are observed to be vitreous goethite. Additionally, samples along the top edge of the iron boomerang and above a Fe oxide FWHM of 360 nm, and with a combined low SWIR dropoff metric value, are predominantly vitreous goethite. The selection of potential ochreous goethite samples can be achieved by selecting samples that have Fe oxide wavelengths greater than 930 nm and lie along the bottom edge of the iron boomerang. It is tempting to infer that a traverse along any of the iron boomerang outer edges might be representative of a two-member spectral mixture, namely hematite and goethite. Further work with known mixtures of hematite and goethite is required to evaluate the potential mixing pathways within the iron boomerang. Additionally, even though previous studies have established a hematite-goethite ratio, it would be beneficial in any future work to assess if the ratios are affected by the type of hematite and goethite used. This could be done when assessing the potential mixing pathways. The ability to identify at least three mineral types, hematite as well as vitreous and ochreous goethite, should allow a selection of representative samples to test the mixing pathways and the effects that they may have on the iron boomerang and the hematite-goethite ratio. Samples that contain spectral absorptions due to the presence of weathering minerals were found to have an impact on the overall distribution of the iron boomerang. The presence of kaolinite was observed to induce a reduction in the calculated Fe oxide FWHM value. Weathered samples are easily masked out and do not present a major issue. In this study, the number of samples that were impacted by the presence of alteration minerals was approximately 33%. It was demonstrated that the iron boomerang, when examined as a per dataset collection, allows an overview of each dataset relative to each other and thus provides a direct comparison of the datasets. However, it is worth noting the impact of crushing and reducing the particle size on the individual spectral samples. The iron boomerang yielded from the Hamersley Basin pulp samples is known to contain hematite, vitreous goethite and ochreous goethite. However, the decreased particle size has seemingly reduced the range of Fe oxide wavelengths and Fe oxide FWHM values that might be expected when the other datasets are examined. It is noted that, in this case, the features that are indicative of vitreous goethite, such as larger SWIR dropoff values and larger Fe oxide wavelength and Fe oxide FWHM values, have been suppressed and give the overall impression of the spectral samples being more ochreous in spectral appearance.