Hand selected Septarian Nodule by Kings Apron.
World renowned as the Septarian "Dragon Stone” geode. Our special hand selection is from Betsiboka Region of Madagascar. The hollow Septarian Nodule cavity is full of beautiful Calcite crystals. 
The phenomenal alchemy history, which can be found below, makes this spectacular display piece a great conversation and educational piece for your home/office/learning environment. 
Septarian nodules originate from the Cretaceous period and formed anywhere between 50 to 70 million years ago! That means that they came about around the same time the dinosaurs become extinct.
Septarian or septarian nodules are concretions containing angular cavities or cracks, called "septaria" which have become filled with calcite and aragonite.
Sea life during that time became attracted to the molten sediment that was produced by these massive volcanic eruptions. Overtime as sea life began to die, their chemical composition became enriched in sedimentary rock, forming the nodules we see today. As oceans began to recede around the world, the water within soon dried out and massive cracks formed internally. The chemicals within the dead sea life eventually crystallized and formed Aragonite “crusts” and drusy Calcite crystals.
The exact mechanism for how the cracks form in the concretions is a mystery. One possible mechanism is the dehydration of the clay-rich core of a concretion causing it to shrink and crack. Another is the cracks being due to the expansion of gases produced by the decay of organic matter within a concretion. Earthquakes have also been suggested as yet another mechanism. 
The cracks in the concretions are then filled in with minerals such as calcite (clear) and aragonite (brown) and sometimes pyrite causing the very interesting patterns, which have often been described as dragon's skin. They are frequently found as geodes with hollow, calcite crystal filled cavities. More rarely the fossils that originally started the formation of the concretion are still preserved in the septarian.