Have you ever noticed a rock that had numerous concentric layers like the sandstone pictured to the left? If so then you’ve seen liesegang bands Strange as they may look these bands occur naturally within many sedimentary rocks and less commonly within igneous and metamorphic rocks. At some point after the rock formed it was buried and saturated with iron-rich ground water and the bands, which are typically an iron-rich mineral such as limonite, precipitated within the rock in repeating rings. Later, it was exposed at the surface and the softer sandstone eroded away leaving the harder rings standing in relief on the rock.
Liesegang bands can form an array of visually stunning patterns. Sometimes they form near-perfect cylinders that resemble iron pipes.