Virus inactivation and virus adsorption, resulting from interactions with minerals, constitute important aspects of an aquifers disinfection capacity. Investigations using a 20 cm column filled with medium-grained natural sands demonstrated that the sands can attenuate up to 62% of a pulse of viruses injected. Experiments using repeatedly washed sands had significantly lower attenuation capacity than fresh sands, due to removal of fine-grained (silt and clay-sized) coatings on grain surfaces. X-ray diffraction analyses of the sand, and the associated fine-grained coating indicated that no significant mineralogical differences existed between these two materials. The experimental data suggested that rougher surfaces/crystal edges in the grain coatings reduced repulsive forces between viruses and the sands permitting greater virus adsorption to the column matrix. Soaking all sands with Tryptone solution after testing released adsorbed viruses indicated that short-term viral inactivation due to interactions with the column matrix was a negligible part of the attenuation process.