On the other hand, non-certified diamonds have not been evaluated by an independent certifying agency, and a retailer can only speculate as to the diamond's quality. If a retailer tells you the clarity, color, carat weight, or cut of a non-certified stone, the retailer is only sharing a best guess.

For small stones or accent stones, you might consider purchasing a non-certified diamond. In smaller diamonds, it can be difficult or near impossible to view quality characteristics with the naked eye. However, GIA does offer special testing for loose and mounted diamonds in smaller sizes. Testing for diamonds less than .2 carats can determine whether your small diamonds are natural and whether they've been treated.