These rings are very cool

Found them: http://www.omniaoddities.com/#!/r-e-s-i-n-·-b-a-n-g-l-e-s/c/6117983/offset=0&sort=normal

Relatedish: http://projectresonate.com/our-product.html

You also can find plenty of these on Etsy. Search for resin ring / rings.