"Various tests were performed on 12 domestic and foreign oil shales to ascertain differences or similarities of the structure of kerogens and the composition of the soluble organic material associated with the kerogens. The oil shales varied in geologic age, environment, source material, and elemental composition. The kerogens were studied by oxidative degradation, pyrolytic degradation and physical property analyses. The associated bitumens were studied by bitumen compositional analyses. The results of this study showed major differences in the structure of the kerogens and in the composition of the associated bitumens. Most of the differences appear to be related by geologic age, but in some instances, the differences are related to source material or elemental compounds."