Septarian Nodule Stone Egg Decorator Rock
A hand cut beautiful Septarian Nodule egg from Utah and it is 2.25 inches or 57 mm tall.
This material was formed when the Gulf of Mexico extended into what is now Southern Utah. Decomposing sea life (especially seashells) had molecular attraction for the sediment surrounding them, forming mud balls. As the ocean receded, the balls dried and cracked. The oceans returned, depositing more sediments. Aragonite then formed on the edges of the cracks and yellow Calcite crystals formed in the spaces.
The name comes from the Aragonite dividing ("septurn" in Latin) the calcite from the clay.