Liesegang rings (geology)
Liesegang rings (; also called Liesegangen rings or Liesegang bands) are colored bands of cement observed in sedimentary rocks that typically cut across bedding. These secondary (diagenetic) sedimentary structures exhibit bands of (authigenic) minerals that are arranged in a regular repeating pattern.
Source: Wikipedia — Liesegang rings (geology) (CC BY-SA 4.0)