ineralogical processes in soils and sediments provide an important control on trace metal abundance and distribution in natural and contaminated environments, and can ultimately govern whether soils and sediments act as a sink or a source of trace metals to surrounding waters. In particular, despite their relatively low abundance, iron and manganese minerals can provide a first order control on trace metal cycling, through coupled sorption and redox reactions. These interactions at the mineral-water interface are well known to strongly influence metal speciation and isotopic composition, and also metal concentration and distribution between the solid and aqueous components of soil and sediment systems. The effect of soil and sediment diagenesis on the mineral-water interface however, is less well known, and it is unclear how the aging and transformation of iron and manganese minerals influences the mobiity and ultimate fate of metals in soil and sediment systems. Here we use a combination of advanced, high resolution analytical techniques, including transmission electron microscopy and X-ray absorption spectroscopy and microscopy, coupled with laboratory sorption and isotope fractionation experiments, to investigate the reactivity and cycling of trace metals in the terrestrial and marine environments, focusing on the sorption and diagenetic processes that control metal cycling between soils and sediments and associated waters. We will exemplify our work with case studies focusing on the contrasting behaviour of nickel and cobalt in soils and sediments during sorption to and diagenesis of managense oxide minerals. We will focus on the processes that control the initial sequestration of these metals into their host mineral phases and the subsequent alteration of the primary host phases during soil and sediment diagenesis. We will show that a combination of molecular level mineralogical processes occurring during metal sequestration and diagenesis provide a first order control on the global cycling of nickel and cobalt in the terrestrial and marine environments.