Spectral characteristics of chlorites and Mg‐serpentines using high‐resolution reflectance spectroscopy

The present laboratory study using high‐resolution reflectance spectroscopy (0.25–2.7 μm) focuses on two primary phyllosilicate groups, serpentines and chlorites. The results show that it is possible to spectrally distinguish between isochemical end‐members of the Mg‐rich serpentine group (chrysotile, antigorite, and lizardite) and to recognize spectral variations in chlorites as a function of Fe/Mg ratio (∼8–38 wt % Fe). The position and relative strength of the 1.4‐μm absorption feature in the trioctahedral chlorites appear to be correlated to the total iron content and/or the Mg/Si ratio and the loss on ignition values of the sample. Spectral differences in the 2.3‐μm wavelength region can be attributed to differences in lattice environments and are characteristic for specific trioctahedral chlorites. The 1.4‐μm feature in the isochemical Mg‐rich serpentines (total iron content ∼1.5–7.0 wt%) show marked spectral differences, apparently due to structural differences.