Methods for estimating the amounts of nahcolite, dawsonite, and the sum of these two sodium carbonate minerals from oil-yield assay data are developed and evaluated for Green River Formation oil shales from the saline sections of Colorado's Piceance Creek Basin. Derived statistically, these estimation methods depend on the fact that these minerals yield water and gas measured during oil-yield assay. The estimation procedures yield values for nahcolite and nahcolite-plus-dawsonite of sufficient accuracy for stratigraphic plotting and correlation, whereas estimates for dawsonite are more generalized. However, resource estimates and reserve computations for both nahcolite and dawsonite accurate within 10 percent of the real value are readily available by assuming the mineral amounts calculated by the procedures presented. These estimation procedures are applicable to oil-yield assay data on core samples from more than 30 coreholes which have penetrated the saline section of the Green River Formation in Colorado. Work done in cooperation with the University of Wyoming.