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Igneous rock types can be roughly determined from the wavelength position of the minima of absorption and emission, or the maxima of reflection, in their infrared spectra. Emission analysis is the method most attractive for field operations, particularly from aircraft or orbiting vehicles. The usefulness of the method is severely limited by surface roughness, small particle size (less than 50 microns), and physical discontinuities within the emitting surface.
R. J. P. Lyon (Tue,) studied this question.