2-3"
Random pull 
Your piece will be (if not the exact picture) quite similar!
 
Septarian are strong Shamanic stones harnessing the different vibrational energies of the stones they are made up of.  A combination of calcite, limestone (chalcedony) and aragonite, this stone brings a very calming, protective energy that is ancient and magical.
 
Please see our Crystal Lore Section for more info on this amazing stone!