Septarian Geode

Septarian, also known as septarian nodules or septarian concretions, is a distinctive type of sedimentary rock that often contains crystals. These nodules typically form in mud-rich marine environments. The term "septarian" refers to the characteristic pattern of cracks (septa) that radiate outward from a central cavity, creating a unique and eye-catching appearance.

The exterior of septarian nodules is often rough and can be brown or gray, while the interior reveals intricate patterns of angular cavities filled with various minerals. The most common minerals found in these cavities include calcite, aragonite, barite, and occasionally other minerals like quartz.