Dendritic Agate double band ring Sz 10Gorgeous Dendritic Agate set in sterling and fine silver with a double band. Size 10. Dendrites, a Greek word for tree like, are inclusions that appear organic due to their plant like structure, but they are actually inorganic traces of iron or manganese. The iron and manganese ions gain access to the forming stone as weathering solutions from neighboring rock. The impurities crystallize inside the agate in branching formations seeping through fine