I have a bunch of jewelry that I no longer wear nor want. Any places that buy either by the weight or piece. Most of it is gold - necklaces, bracelets, earrings. I also randomnly have 1 diamond earring.
My only advice is to make sure you check whether they will pay you for the stones - some of them ONLY want gold and will basically make money on the stones, but won't pay you for them. I think the places like West Seattle Coins or something will do that, but the money for gold places in the mall won't. Just be sure to ask!
(I haven't ever sold anything, but looked into it briefly because my dad wanted to sell a gold ring)