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We performed K-band observations of the Uranian rings during the 1985 opposition in order to determine if a measurable opposition effect occurs. The investigation, carried out over a period of several months and over a range of 0.021° to 2.5° in solar phase angle, revealed an opposition surge of approximately 0.2 mag. This result is interpreted in terms of two simple models: mutual shadowing and surface microstructure. If entirely due to interparticle shadowing, the brightening implies a ring thickness inconsistent with surface mass densities derived from dynamical considerations. If the surge results from surface effects, the ring particles have dark surfaces with a porosity comparable to that of terrestrial snow.