Chip Formation in Anisotropic Rock In a series of previous papers it was shown that the fracture of brittle materials such as rock subjected to a globally compressive stress field is accompanied by the formation of microdamage regions. Quantitative descriptions of these regions exist for isotropic materials. In the present paper the theory is extended to brittle materials which exhibit anisotropic fracture behavior due to the presence of a preferred prefracture flaw distribution. Results are computed for three orientations of a given flaw distribution and compared with some existing theoretical and experimental isotropic results. A new type of chip formation, not found in the isotropic case, involving multiple initiation sites, is predicted.