Characterizing filter media mineral coatings using analytical techniques from geological science helps unlock fundamental filtration phenomena.Fundamental analytical techniques from the geological sciences were employed to characterize the surface coatings found on anthracite and sand filter media from a variety of full‐scale water treatment facilities. Attempts were made to relate the presence of various chemical surface coatings to the process chemistry used at the facility, the presence of various chemical species (e.g., manganese) in the raw water, or both. The authors also considered the role that such chemical oxide surfaces may play in the overall performance of filtration systems.