The best choice would be to find a local Diamond buyer. Some web-based Cash for Diamond companies have been exposed as paying as little as 5% of the actual diamond's value. Plus you have to send your jewlry away without knowing what they will pay and if they are being honest.
When you sell Diamond locally, you can request that the buyer weighs your items in front of you, and you can get his offer without being required to sell.
By following this simple guide, you can be sure you will receive a fair price for all diamond jewelry!