A series of experiments were conducted to provide insight into the chemistry and mineralogy of spent western and eastern reference oil shales. The solubility of CaMoO{sub 4} was determined and the results used to evaluate the occurrence of CaMoO{sub 4} in spent western oil shales. The influence of oil extraction process, solid-solution contact time, and recarbonation on spent oil shale leachate chemical composition was examined. The mineralogy of spent eastern oil shale was characterized, as was the mineralogy of hydrated and recarbonated spent western oil shale samples. Some shortcomings associated with the use of geochemical models were identified. The use of geochemical models to predict leachate composition was also illustrated. 69 refs., 17 figs., 19 tabs.