Have you ever seen such a beautiful concretion? Prop up this polished cube to see the dozens of crevices filled with crystals of yellow calcite and rivers of brown aragonite! 

Septarians are concretions that have cracks or "septoria" filled with minerals like calcite (the yellow), aragonite (the brown) and limestone (the gray rock). Concretions were formed millions of years ago as decaying organic matter mixed with sediment. Septarian has been known to be called "dragon stone" as its cracked surface gives the allusion of the skin of a dragon. 

Size: 2.38 x 1.63 x 2.5 inches

Weight: 8 oz.