2.0 Introduction 3.0 Experimental Technique 3.1 Sample Acquisition and Preparation 3.2 Sample Characterization 3.3 Acquisition of Spectra 3.4 Data Storage and Retrieval 4.0 Discussion of Spectra 4.1 Major Spectral Features of Minerals 4.2 Effect of Particle Size 4.21 Role of surface and volume scattering 4.22 Changes in spectral contrast 4.23 Transparency peaks 4.24 Christiansen frequency 4.3 Effect of Crystal!ographic Orientation 4.4 Effect of Packing 4.5 Effect of Atmospheric Gases 4.6 Effect of Impurities 4.7 Using Laboratory Spectra to Predict Remote Sensing Measurements 5.0 Acknowledgements 6.0 Appendix 1: Mineral spectra and description sheets are presented in alphabetical order. Minerals are listed alphabetically and by mineral class, subclass and group at the beginning of the appendix.

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Fundamental molecular vibration bands are significantly diminished by scattering. Thus such bands in spectra of fine particulate regoliths (i.e., dominated by <5‐μm particles), or regoliths displaying a similar scale of porosity, are difficult to use for mineralogical or rock type identification. Consequently, other spectral features have been sought that may be more useful in spectroscopic remote sensing of composition. We find that mineralogical information is retained in overtones and combination tones of the fundamental molecular vibrations in the 3.0‐ to 7.0‐μm region, but that relatively few minerals have a sufficiently distinctive band structure to be unambiguously identified with currently available techniques. More significantly, identification of general rock type, as defined by the SCFM chemical index (SCFM = SiO2/SiO2 + CaO + FeO + MgO), is possible using spectral features associated with the principal Christiansen frequency and with a region of relative transparency between the Si‐O stretching and bending bands. However, environmental factors may affect the appearance and wavelengths of these features. Finally, prominent absorption bands may result from the presence of relatively small amounts of water, hydroxyl or carbonate, because absorption bands exhibited by these materials in the 2.7‐ to 4.0‐μm region, where silicate spectra are otherwise featureless, increase strongly in spectral contrast with decreasing particle size. Such materials are thus detectable in very small amounts in a particulate regolith composed predominantly of silicate minerals.

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