Wide-angle x-ray diagrams of quartz (Bragg and Laue case) showed along the lines of weak and of missing reflections (forbidden ones) a rather close sequence of “umweganregung” spots. These spots were indexed by a special method. With the crystal surface etched or polished, the form of the spots was as expected. With the surface ground, the spots along the forbidden lines showed double-spikes, their directions varying from spot to spot as well as with the source-to-crystal and crystal-to-film distances. The spikes are considered as a special kind of reflection broadening produced by the mosaic structure of the crystal surface. Each of the two reflections contributing to an umweg reflection consists of two components: the first is rather divergent because it is produced by the mosaic layer formed by grinding; the second is just slightly divergent because it is produced by the crystal matrix which proved to be nearly perfect. The combination of the narrow but intensive component of one reflection with the wide component of the other results in a double-spike. This idealizing concept, mathematically formulated by means of vectors in the reciprocal lattice, quantitatively explained the observed directions of the spikes.