Septarian Nodule Polished End-Cuts (Bargain Flat) - 13 Pieces


This is a flat of 13 cut and polished Septarian nodules from Utah. Unfortunately they all incurred some slight damage while being shipped to us from our supplier. Most of them have a single, small chip to the edge of them. They are still beautiful pieces, which we would typically retail for $25-35 each. Because of the damage we are selling them the lot at an average price of $5/each.

They show beautiful patterns with a nice polish and range from 4.1 to 5.2" wide. The base of each nodule has been cut flat so that they sit nicely on a flat surface.

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 a suggested as yet another mechanism.

The cracks in the concretions are then filled in with minerals such as calcite (yellow) and aragonite (brown) and sometime 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.
West of Orderville, Utah
Frontier Formation
4.1 to 5.2" wide