Spectral signatures of rocks and mineral provide information on their chemical composition and crystal properties, grain size and roughness over a wide range of wavelengths from the visible to the thermal infrared. For example, the iron-rich minerals are characterized by low reflectance (high absorbance) below 0.7 μm, carbonates show a typical absorbance feature around 2.3 μm, the water content can be instead evaluated by the depth of absorptionat 1,4 and 1,9 μm. Particualrly importantant are the spectral signatures which rocks exhibit in emissivity in the Thermal Infrared (TIR) spectral region. For instance looking at the shift of lower emission band of SiO2 from around 9 up to 10 μm as far as its concentration reduces e.g. moving from granite to peridotite.
Describe the spectral regions where Mineral and Rocks exhibit their main signatures
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