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Continuum-removed visible/near-infrared reflectance spectra, offset for clarity. Spectra of O2-oxidized samples that experienced additional exposure to air during storage and transport are plotted as dotted lines. The spectra of two smectite standards, nontronite NAu-2 and ferric smectite SWa-1, are included for comparison. Vertical lines at the band minima for (Fe3+Fe3+)-OH and (AlFe3+)-OH in nontronite are included for reference.
