I think Tibetan district is the first place I would look for something like this. I’ve been in a few shops there that have very high quality and expensive stones for sale, which can be set into jewelry or worn as bracelets and necklaces. You rarely see Chinese people wearing that type of stuff, but they have jade and other stones available for sale near temples like Wuhou Ci, which is right on the edge of the Tibetan district in Chengdu.