We have measured crustal absorption, expressed as a wavelength dependent imaginary index of refraction (nIM) at both visible and infrared wavelengths. Measurements at visible wavelengths show values of nIM that range from ~0.02 at 300 nm to ~0.004 to 700 nm. Infrared measurements show an absorption that is dominated by a silicate absorption with a maximum value of nIM~1 near 10 μm. Comparisons of our measurements with other reported measurements of well-documented crustal aerosols show a great deal of similarity among the measured values. We have shown that these measured optical properties, and the similarities and differences in the measured values, can be understood in terms of mineralogical characteristics of the aerosol and fractionation processes that occur in the generation and transport of these aerosols.