the diamond industry is mainly built around selling to consumers, not buying back like gold or silver. if you try to sell a diamond, most buyers will only offer close to the raw or wholesale price. keep in mind, the market is flooded with diamonds, and most dealers are looking to turn inventory into cash, not hand out cash for yours. for certified stones, you might get around 20% of the original price, maybe 30–40% if it’s a really nice piece and you’re lucky. if it’s not certified, chances are they won’t even make an offer.