Simply immerse the loose stone in water. Because loose diamonds are so thick, they should sink to the bottom of a glass of water if dropped in. Because they are less thick, many diamond imitations, including glass and quartz, may float or sink more slowly. Always check with a gemologist before you buy a diamond. However, if you wear your diamond ring all the time, it can be worn down by constant movement and use. This will cause the diamond to need cleaning or polishing. If you don't clean it regularly, the dirt will scratch the surface of the stone preventing it from reflecting light as well as it could. Also, some chemicals used during cleaning processes might remove the superficial coating of metal that protects the diamond's surface. In this case, the diamond would need to be re-coated. The re-coating process involves covering the diamond with layers of other metals or compounds. These can include gold, silver, platinum, or carbon. The goal is to produce a smooth finish that doesn't show the original texture of the diamond itself. Real diamond jewelry tends to be more expensive than its imitation counterparts because they are made up of multiple gems set into one piece. Imitations often use cubic zirconia or glass for their stones. While these materials can look like diamonds on the outside, they aren't actually diamond inside. Only real diamonds can truly reflect light and create sparkle.