Past and present (a)biotic soil processes can be preserved by mineral surface coatings, which can sequester contaminants in soils and sediments. The coatings can contain complex assemblages of nanometer-size minerals and organic components. The formation, composition, and morphology of these complex mineral assemblages depend on, and hence reflect, the mineralogical and chemical composition of the substrate they develop on and the environmental factors in the surrounding soils and sediments. Mineral surface coatings typically contain complex and variable porosities, many with regions of limited fluid flow. Low-flow conditions, combined with different nanometer-size phases in the interior of mineral surface coatings, allow coatings to sequester contaminant-bearing solutes, complexes, and nanoparticles.