Septarian specimens are believed to have formed during the Cretaceous period when sea levels were much higher. Volcanic eruptions and other occurrences resulted in the death of small sealife that then sank to into the seabed. As the specimens decomposed, sediments would accumulate and create a nodule or mud ball. When the oceans eventually receded, these mud balls were left exposed to the air and dried out, causing shrinking and cracking. The beautiful patterns you see inside septarian nodules are the result of this cracking. Each one so unique in patterns. 
Septarian Crystals in general are beautifully grounding , healing and protective. 
 
* measures approx 5 1/4"  x 5 "