The mechanical properties of coal are often represented by the orthotropic material model, which consists of nine elastic constants. The material symmetries involved are found in coal primarily because of the natural process by which the coal was formed. In this report, the material properties of five U.S. coals, as obtained from cubical testing, are examined using the assumption of the orthotropic material model as a basis for comparison. An analysis is performed on each set of coal material data in order to examine its conformability to other, less complex material models-- the transversely isotropic model consisting of five elastic constants and the isotropic model consisting of two elastic constants. In addition, the material properties of the two U.S. shales are analyzed, based on the assumption that they comply with the transversely isotropic model. An analysis similar to that performed on the coal material is applied to the shale to determine the conformity of its material properties to the isotropic model.