For the expansion of the functionality of diamond crystallites by modification of surface morphology, catalytic etching of synthetic diamond crystallites at 1173 K by iron, which were loaded by the impregnation method using an aqueous solution of iron nitrate; in a streaming mixed gas (pH(2) = 0.1 MPa, pN(2) = 0.9 MPa), has been investigated by scanning electron microscopy (SEM) and Raman spectroscopy. The dependence of the crystal planes {111} and {100}, of the diamond crystallites and the loading amount of iron on the diamond on the etching behavior by iron particles, the morphology of the etch pits, and potential formation of iron carbide through the catalytic etching, were discussed. (C) 2012 Elsevier B.V. All rights reserved.