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Aqueous solutions with about 10 ppt 195Au and [HC1] of 10-2.3 and 10-1.3 m were exposed to solid minerals for several months. The gold uptake with time was observed by time-stepped sampling and radiochemical Au analysis. Sorbants were polished thick sections of quartz, pyrite, pyrrhotite and elemental gold, as well as crushed grains and sawed mineral cubes of quartz and pyrite (all randomly oriented). The kinetics of gold sorption strongly varied with the surface area of the sorbents, the type of mineral and the pH of the solution. Mineral-specific differences in reaction rates were observed only at experimental pH values around 2.3, where sorption on pyrrhotite and elemental gold was much more rapid than by quartz and pyrite. At pH around 1.3 gold sorption was rapid on all minerals. This finding is thought to reflect the gold speciation, i.e. neutral hydroxo-gold complexes above pH 1.5, for which only chemisorption is possible, versus dominantly AuCI2 below pH 1.5, where unspecific electrostatic interaction enhances reaction rates with all protonated mineral surfaces.Metal contents in aqueous environments are controlled by mineral solubility and sorption reactions. These processes depend on the kinetics of mass transfer which is the reason why thermodynamic equilibrium is often not attained. Sorption provides a mechanism by which solution components far below bulk saturation can be fixed at mineral/solution interfaces, a process which may be particularly important for the formation of supergene and hydrothermal precious metal mineralization (Bakken et al. 1989;Bancroft and Hyland 1990;Knipe et al. 1991).The importance of sorption processes in the low-temperature geochemistry of gold is also shown by the fact that surface fresh water has gold contents of 1-10 ppt (McHugh 1988) and sea water has only 0.001-0.003 ppt (Falkner and Edmond 1990), whereas the calculated gold solubility as the species AuOH(HzO) ~ in oxygenated solutions is a few ppm (Vlassopoulos and Wood 1990). Experimental sorption studies show a strong dependence of gold-sorption on aqueous gold speciation, pH, and the physico-chemical nature of individual mineral surfaces (reviewed in Renders and Seward 1989;Bancroft and Hyland 1990;Machesky et al. 1991;Schoonen et al. 1992).Most of the previous studies had experimental constraints which focused on equilibrium situations and had extremely high contents of solute Au when compared to natural environments. We present here some preliminary data on gold uptake by a set of minerals as a function of time. The gold content of the experimental solutions was about 10 ppt, i.e. close to natural surface fresh water.There are a wide variety of possible gold-sorption reactions due to the number of solute-gold species and the number of different nucleation sites on mineral surfaces. An unspecific or physical adsorption can occur by electrostatic interaction between any charged gold-bearing complex and oppositely charged mineral surface. The charge of mineral surfaces in aqueous environments is typically related to...