The circle has been formed from copper wire, which has then been hammered to give a textured finish using a vintage hammer. It is finished with a shard of reticulated sterling silver and hangs on an 18 inch 1mm ball chain necklace.
Reticulation is a process whereby sterling silver is heated, quenched and pickled repeatedly. This removes some copper from the alloy concentrating the remainder at the core and allowing a pattern to be formed on the surface. The resulting surface texture is completely organic, so each piece will be different and cannot be replicated.
This has been coated with a wax polish to protect the finish, but this will come off with wear, so it will naturally discolour with exposure to moisture, oxygen, heat, etc. You can polish with a soft cloth and a metal polishing cream suitable for copper and find the shade you like, as the beauty of copper is it has many tones.
Store away from direct sunlight and moisture and avoid wearing while swimming, showering, etc or it coming into direct contact with chemicals, such as perfume, household cleaning products, etc.