A highly polished, freestanding septarian nodule.
The piece pictured is exactly the piece you would receive, and with between 250-500g (~0.5-1lb)
This would definitely be a great piece of home decor or addition for a collector!
Septarian nodules were formed about 50 to 70 million years ago during the Cretaceous Period in what is now southern Utah and, back then was a sea bed. Volcanic eruptions in the era killed sea life which had a chemical attraction for the sediment around them, creating mud (clay) balls. As the seabed dried, the balls were left to dry and crack. As calcite from the dissolved shells was carried into the cracks in the balls, yellow calcite crystals formed. A thin wall of calcite was transformed into the brown aragonite separating the gray bentonite heavy clay exteriors from the calcite centers.