aureole (ôrˈēōlˌ) [key], in physics, luminous circle seen when the sun or other bright light is observed through a diffuse medium, i.e., smoke, thin cloud, fog, haze, or mist. It sometimes occurs as a series of concentric circles. The aureole results from the dispersion of light by particles of dust or water. Because of the refraction of the light waves, it exhibits color in varying intensities. In geology, an aureole zone is where rocks show the effect of contacting intruding, hot igneous rock, also called contact metamorphism.