Hi there. I am selling this Rare Banded Rhodochrosite carved egg from Argentina. This is from a stalactite, or perhaps a stalagmite which formed as water dripped within a cave depositing minerals as the water evaporated. Over thousands of years these minerals build up, layer upon layer to form stalactites and stalagmites. If you slice though one of these formations you can see the layers. This piece has been polished where it was cut to reveal the banded layers. The layer can change color as the minerals within the water change over time. These rhodochrosite pieces are really rare and are becoming harder and harder to find. Thanks so much for visiting my store and have a great day!.