Below are tips on how to find a lost diamond ring. Fluorescence Most diamonds have this property, which makes them glow under UV light. Get a black light and sweep the room. Look for a blue glow coming from under the couch or the coffee table, because that could be your lost diamond.       Use Hands and Feet Diamonds are hard, and cut diamonds are sharp as well. Feel around for your stone using your bare hands and feet, especially if you have a thick carpet whose fibers could be covering up the stone. Expect it to Have Gone Anywhere Diamonds do not roll the way balls do, because they have unusual shapes. This means they will likely end up in spots you would not expect them to be. Assume nothing, and cover every inch methodically. They Attract Grease This can be a good thing, especially if your beloved stone just fell down the sink. It may be stuck along the way, so get a flashlight and check that out.