Atomic force microscopy (AFM) observations and profile measurements by a three-dimensional measuring system were carried out on the surface microtopographs of the r, z, m, and Z faces of synthetic quartz crystals, and the differences of growth mechanism between smooth and rough interfaces were examined. We demonstrated that the r, z, and m faces grow by a spiral growth mechanism, whereas the Z face grows by an adhesive-type mechanism. We found that the formation of cobbles on the Z face is due to morphological instability, and the step-like patterns observed on type 11 cobbles appear due to the instability generated by mixed dislocations. (C) 2003 Elsevier B.V. All rights reserved.