The regular zones or bands of precipitated chemical materials, when a mineral such as red iron oxide (which precipitates from an aqueous solution as a catalytic agent) moves through into undisturbed solution to reinitiate the process. This process again results in precipitation of iron oxide into a narrow band, freeing the catalytic agent to continue its movement through the solution or silica gel. This banding is called ‘Liesegang banding’ and forms in response to diffusion controlled movement of iron and oxygen in the solution or rock.