An account is given of optical and interferometric studies on spiral patterns which have been found on the basal planes of synthetic quartz crystals. These patterns have high visibility and show both single and interlaced triangular spirals, of but a few turns, and always enclosed within a linear boundary. The topographies of the spirals are studied with the help of a new, highly sensitive, accurately contouring, thin-film multiple-beam interference technique which is described. The spirals differ in character from the usual growth spirals, being in effect shallow ruts running round hillocks. It is proposed that these spirals arise from an etching or solution mechanism.