Precision multiple-beam interference methods are applied to the study of the topography of octahedral faces of three diamonds. A new crossed fringe technique of high sensitivity is described. Evidence is adduced to support the view that the curvature of diamond faces and the occurrence of triangular pits are to be attributed to growth and not to solution. The observations thus settle a long-standing controversy. Irregular depressions which are observed are attributed to a solution mechanism. New features associated with the triangular growth pits are described and interpreted. A crystal surface with regions showing an abnormally high degree of optical plane uniformity is described. The surface of a polished diamond is described.