3.2" Cut/Polished Septarian Nodule Half - Morocco

This is a cut and polished septarian nodule from Morocco. Only the pictured half of the nodule is included, however it is accompanied with an acrylic display stand to assist with presentation. The nodule half is 3.2" wide and contains a beautiful and unique inner structure.

Septarian is a form of sedimentary geode that formed on sea beds millions of years ago. When they dried out they cracked and formed hollow interiors. The interiors usually become either partly or completely full with other minerals, such as calcite, giving septarian its unusual texture and features. Calcite was carried down into the cracks of the mud balls and calcite crystals formed.

Septarian or septarian nodules are concretions containing angular cavities or cracks, called "septaria" which have become filled with calcite and aragonite. A concretion is 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.
3.2" wide (each)