Patterns that formed spontaneously upon heating thermally evaporated thin films of gold (Au) and chromium (Cr) on silicon (Si) substrates to 500 °C were investigated. A variety of patterns were observed. The type of pattern formed correlated with the thickness ratio of Cr to Au. The most striking pattern consisted of concentric rings spaced approximately 10–30 μm apart. Each ring was composed of pits 2–5 μm in length, which extended 200–400 nm into the silicon substrate. While concentric patterns are widely seen in chemical reaction-diffusion systems, pattern formation in the heated Au/Cr/Si system has not been previously observed.