This pendant focal element in solid copper with fire patina can be worn as is or be used to trap a stone, polymers, sea glass, a large pearl or whatever your muses whisper. Set a stone into the cup and lightly press the sides closing it a bit to be sure it will not fall. 
One of a kind it measures total 82mm x 58mm approx.
 
https://metalpearlsfireandstoneblog.wordpress.com/2022/09/23/focal-pendant-setting/