The existence of large-sized satellite faces on crystals of the mineral calaverite (Au1-xAgxTe2) is reported. These anomalous high-index faces can be related directly to the wave vector q of the displacive incommensurate modulation recently found in the crystal structure. If we extend the classical morphological law of rational indices to include q as a fourth basic vector, the high-index faces can be described by four low integers (hklm).@en