One of the most common ways to be paid by jewelry stores when you Sell Diamonds Long Island is by giving you store credit. This is great if you want to upgrade to a better diamond, but otherwise it is almost worthless. You cannot go on a vacation with store credit nor can you pay off your credit cards with store credit. When you Sell Diamonds Long Island you want to be sure you are being paid in cash. Not check, not a gift card – cash. Not all diamond buyers are capable of doing this – especially when a high quality diamond can pay upwards of $10,000.