This "Dragon Egg" is crafted by carving a truly fantastic septarian nodule from the Betsiboka region in Madagascar. It's a septarian nodule filled with beautiful calcite and aragonite crystals, carved and polished into an egg shape. The natural pattern of the septarian cracks gives it the appearance of a dragon egg. A spectacular display piece that would look great at home/office or would be a fantastic gift for the Game of Thrones enthusiast you know! Septarian nodules or septarians are concretions containing angular cavities or fissures, called "septaria", 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 marine life in a marine environment. The exact mechanism by which 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. The cracks could also be caused by the expansion of gas produced by decaying organic matter within a concretion. Earthquakes have also been suggested as another mechanism. The fissures in the concretions are then filled with minerals such as calcite (yellow), aragonite (brown), and sometimes pyrite, resulting in very interesting patterns. They have often been described as resembling dragon skin. They are often found as geodes with hollow cavities filled with calcite crystals. More rarely, fossils that originally initiated the formation of the concretion are still preserved in the septarian.