A novel type of experiment was developed where the crack initiation of medium-grained granite was studied in detail. Flat specimens with a discontinuous width were loaded in compression and the strain was measured by strain gauges on the sides and displacements by Digital Image Correlation on the flat surface. The cracking process was studied using acoustic emission monitoring. The specimen geometry yields a stress concentration with a mixed tensile and shear stress state. Specimens with three different discontinuity sizes were tested to study the discontinuity size in relation to the grain size. The results show that the discontinuity size affects both when crack initiation occurs and the crack propagation path. The crack patterns were assessed using images taken on the specimen during loading.