Quartz is an anisotropic mineral, and each mid-infrared (7–15 μm) reflectance spectrum collected from an individual quartz crystal is strongly influenced by its orientation. As a result, quartz reflectance spectra contain features that systematically change with orientation. In this study, the trough at 8.63 μm was used to derive crystal orientation information from quartz reflectance spectra collected using a high spatial resolution spectrometer with a 100 × 100 μm spot size. The intensity of this trough was quantified using two band ratios (Ref8.48 / Ref8.63 and Ref9.01 / Ref8.63), and band ratio Ref8.48 / Ref8.63 was used to infer the orientation of quartz crystals in an Archean granite sample to characterize any fabric.

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