More references are info are here: http://www.metmuseum.org/collection/the-collection-online/search/464788?=&imgno=0&tabname=object-information It's glass cabochon in the center and silver for the ring.
This is my first serious use of ZBrush after casually using Mudbox for a while. The reference is taken from the Metropolitan Museum of art's collection online. My goals here are to not only to learn ZBrush, improve my sculpting but my material definition as well. I will be going for photo realism. I am not sure how far to…