There are three places you can sell diamonds: in a jewelry store; in an online store; or as a private seller.If you sell diamonds in a jewelry store, this is probably the best bet that you are going to make a decent profit. You will have a steady stream of customers coming in to buy your products (of course assuming that all the difficult legwork of marketing and so forth have been readily achieved, and people know about your store). Marketing, that being said, is key. People have to know about your store to go there. If people aren't aware that your store deals in diamond jewelry, how will they ever know to come to your store if that is what they are in the market to buy? That being said, you should always know your customers. Are the people in your store coming in to buy engagement rings