"Ancient Roman Glass" 2" Earrings - Bezel-set Tiny Round Tiles of 2,000-Year-Old Ancient Roman Glass, with a Trio of Seed Pearl Dangles, Sterling Hammered Drop & French Hooks
The iridescence is caused by being under the earth for thousands of years - it's mineral deposits! So, it's best not to get these wet - of course, that's true for all jewelry! :)