7.3" Septarian "Dragon Egg" Geode - Black Crystals

This is a really cool septarian "dragon egg" geode collected in the Betsiboka Region of Madagascar. The hollow cavity is full of beautiful black an brown calcite crystals, and the mud pockets are loaded with ammonite cross sections. It is a hollow septarian nodule which has been polished into an egg shape, and the natural cracked pattern of the septarian gives it the appearance of a dragons egg. A spectacular display piece which would look great in your home/office or make a great gift for the Game of Thrones enthusiast you know.

Comes with the pictured display stand.

There are multiple spots of gap fill around this specimen, this has been reflected in the price.

Septarian or septarian nodules are concretions containing angular cavities or cracks, called "septaria" which have become filled with calcite and aragonite. A concretion is a hard, compact mass of rock that often forms around decaying organic matter. In the case of septarian nodules the concretions formed around decaying sea-life in a marine environment.

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 (yellow) 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.
Septarian with Calcite
Ambondromamy, Betsiboka Region, Madagascar
7.3" tall, 5.3" wide