Septarian dragon eggs are Septarian nodules that have been carved and polished into a egg shape. The natural, cracked pattern of the septarian gives the surface of these polished stones a "dragon skin" look, hence the popular name. Septarian geodes are a specific geological formation, that occur when minerals (primarily calcite and aragonite) fill in cracks in a concretion. This creates a very unique patterning and often leaves hollow spaces inside, forming the geode. These Septarian dragon egg geodes are from Madgascar and were formed during the Jurassic period, around 150 million years ago.