A set of sediment “resuspension” experiments was designed to test various aspects of previously hypothesized clay reconstitution reactions in nearshore sediments. Aliquots of wet sediment of approximately equal weight from Flax Pond, Long Island Sound were suspended in stirred and aerated, high salinity solutions having variable adjusted initial dissolved Si concentrations but otherwise nearly identical properties. Dissolved Al and Si and the water pH were monitored over the course of three days. Dissolved Si was removed from solution in the high initial Si (325 and 650 μM) containers, while little change in Si concentration was observed in a “blank” and 0 Si-spike container. Short-term dissolved Al production in the experiments suggests that clay dissolution is important in these sediments. Long-term dissolved Al behavior agrees fairly well with quantitative predictions based upon previous studies of nearshore sediments, where authigenic clays were believed to cause observed inverse relationships between dissolved Al and Si. The unambiguous results give strong evidence that inverse Al-Si relations in dissolved Fe-poor sediments are a direct result of mineral precipitation, rather than being due to some fortuitous combination of unrelated reactions affecting Al and Si. The Si Al composition of authigenic clay precipitates in marine sediments probably varies directly with the dissolved Si content of contacting waters. This indicates that a combination of “weathering” and “reverse weathering” of minerals may affect Si distributions, and provides a theoretical link between these two sets of previously suggested mechanisms for clay reconstitution in sediments.