I just took mine to my jeweler and have some info. The base metal is copper and the finish is very delicate. They tried to polish on one of the links and the finish came off and exposed the pink copper underneath. They replated that part and were able to gently clean it with baking soda and water, and it looks much better. Just an FYI- whatever manner of cleaning you use, proceed with caution and test it first on an obscure part of the necklace.