Selling a jewellery of around $10,000 is more than a tough issue. You can try with ebay, but not sure regarding the possibility of success. Nothing coming to my mind which can help you!
Go to a reputable jeweler and get it appraised. Then see if they can recommend any good local Jewelry auctions or dealers that might be interested. Remember what you think it might be worth, doesn't mean you will get what you want. Selling high priced Jewelry on a site like eBay will only bring you problems. People like to see what they buy when it comes to things like that. -KiKi
Try Uploading on Social Networking Sites like Facebook, Pinterest maybe someone of your friends get you a good deal.
sell it on Amazon. They are easy to sell jewelry items, because that is supported by profesional marketing members all over the world.
Try the local jewelers, if price for the jewelry is not set, hit local jewelers and ask for the price as a buyer for the almost-same if not same necklace to obtain an idea of price range. But again, try local jewelers to avoid any issues.