Are there any lore-established unusual materials that a fae jeweler might work with?

Asking strictly for flavor, not creation of a practical item. My character wants to make an engagement ring for her suitor with materials that have a personal significance of some sort. The gem is a valuable aquamarine found at the bottom of a crystal-clear stream (having been one of many items thrown there by weirdo cultists to some weird-ass god.) She's currently in a demi-plane among mostly a bunch of friendly fey creatures, and would like to find one of them to set the gemstone in an unusual ring of some sort.