$50 · Septarian Nodule

Septarian Nodule, this piece is about 8" in size. fossilized mud ball (concretion) from ancient seabeds, characterized by a grey, limestone-like exterior and internal, cracked "septa" (partitions) filled with colorful, crystalline minerals like yellow calcite and brown aragonite, resembling a turtle shell or geode when cut open, formed from shrinking mud around organic matter 50-70 million years ago.