Septarian is a distinct and visually captivating kind of concretion, characterized by a rounded mass of mineral material that forms within soft sediment. As these concretions dry and contract, they develop cracks, which subsequently fill with other minerals, usually calcite (yellow) and aragonite (brown). This complex process creates a unique network of intersecting veins, resulting in a stone that is both striking and intricate. Septarian nodules are frequently polished to showcase their internal beauty and are highly sought after by collectors due to their distinctive look and fascinating geological heritage.