In this paper, we report a thermochemical etching method to fabricate well-distributed micropatterns with large pattern ratios on diamond crystallites using cobalt (Co) powder. The effect of temperature on the depth and area of the micropatterns on different crystal planes is quantified. Results show that the depth and area of the patterns on the same plane increase with the temperature and that, at the same processing temperature, the pattern depth and area on {100} planes are larger than those on {111} planes. After heat treatment at 850 A degrees C, the pattern depths on {100} and {111} planes reach 4.0 and 3.5 A mu m, and the corresponding average ratios of the pattern area are 54 and 46 %, respectively. The morphologies of the micropatterns on (001), (113), (101), and (111) planes are dependent on the relative orientations between the etched crystal plane and its adjacent planes, and diamond nanoparticles with specific orientations are observed on etched {100} planes. Furthermore, graphite is detected in the etch patterns, suggesting that thermochemical etching process involves the phase transformation from diamond to graphite.