The chemistry of extracts from spent shale disposal environments is controlled by a number of chemical processes including the formation of inorganic complexes and precipitation-dissolution reactions. The objectives of this study were (1) to alter the data base of a geochemical code by including data for different solution species and solid phases that are important to spent shale environments and (2) to predict the chemistry of extracts from non-recarbonated and recarbonated spent shales by evaluating the solid phases controlling the solubilities of major elements such as calcium and magnesium, and trace elements like fluorine and molybdenum. The geochemical code used for this study was the GEOCHEM model. The data base of this code was altered using updated association constants and solubility products for different elements that the authors and others have developed. Three spent shale samples (PPP3, PPP6, and Lurgi) were recarbonated under slightly elevated CO{sub 2} pressure in a specially designed chamber. The non-recarbonated and recarbonated samples were subjected to solubility studies. The total element concentrations and pH of extracts were used as input to the GEOCHEM code to predict the chemistry. The model predicted that silicate phases (produced during the heating process) initially buffered the pH and controlled Ca{sup 2 } and Mg{sup 2 } concentrations in extracts. The GEOCHEM model predicted that after recarbonation, the Ca{sup 2 } concentrations are controlled by calcite. The F{sup {minus}} concentrations in extracts from non-recarbonated and recarbonated spent shales are controlled by fluorite. Further, GEOCHEM predicted that powellite does not control the solubility of molybdenum in non-recarbonated recarbonated spent shale extracts. 27 refs., 1 fig., 2 tabs.