An overview of vis-nir-swir field spectroscopy - Spectral International

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720nm, there is additional and complimentary information in the NIR (700 nm to
1000 nm).
Figure 3. – The plot shows some of the more common cations that can be identified in
the visible range.
For example, chlorites are more detectable in the visible range because there is
less interference from other species compared to in the SWIR range where their
signal is usually low unless chlorites are the dominant phase. Iron oxyhydroxides
(Figure 4) have many distinctive features that allow them to be discriminated
from each other. This allows a discrimination of pH zoning and something not
easily done before. The nickel cation also has diagnostic features in the visible
range that can be detected in nickel laterite deposits and correlated to the ore
zones. Chrome in kimberlite minerals such as chrome diopside and G-10
garnets make spectroscopy invaluable to the identification of indicator minerals.
Manganese is also detectable through features in the visible range.
Garnets, pyroxenes, olivine, selected iron and copper oxides, hydroxides,
sulfates, and for heavy element carbonates, a NIR major absorption feature.
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Fe2+ Fe2+ chlorites
Fe3+ hematite, goethite
Ni Chrysoprase
Cr Cr-diopside
Mn Mn-chlorite
Mn rhodonite
Mn rhodocrosite