Indentation tests are performed on samples of Indiana Limestone and Berea Sandstone under confining pressures ranging from 0 to 2500 psi. The force-displacement data from these experiments are analyzed by comparing them to numerical results obtained for a simplified theoretical model which assumes (1) rigid-perfectly plastic behavior, (2) a Mohr-Coulomb linear yield envelope, and (3) negligible lip formation. In addition, indentation is assumed to be a quasi-static, equilibrium process. The two Mohr-Coulomb parameters cohesive strength (c) and angle of internal friction (ϕ) are bounded by consideration of the following two heuristic conditions: (1) The force-displacement curve generated by a perfectly rough assumption must be an upper bound to the experimentally observed curve. (2) The frictionless solution must be a lower bound. These two conditions restrict ϕ and c to a narrow allowable region in ϕ-c space, and are applicable to more realistic yield conditions, as well.