Spotting a fake diamond is fairly simple once you know the steps.
Cubic zirconia is a synthetic material that to the naked eye can be almost indistinguishable from a genuine diamond stone. When spending a large sum of money on a piece of jewelry, it is important to know that what you're purchasing is an authentic diamond. There are a few simple ways for the everyday shopper to tell the difference between a cubic zirconia and a diamond.
•1 Place a small piece of newspaper behind the stone. If you can read the newspaper through the stone, it is not a real diamond. Diamonds have internal facets that impact their transparency.
•2 Scratch a piece of glass with the stone. Real diamonds are incredibly hard and will scratch glass, while cubic zirconias will not. Be aware that some synthetic stones may produce small scratches, so don't rely on this test alone.
•3 Breathe on the stone as if you were trying to fog up a window. Diamonds are not capable of holding heat, so if the fog does not clear immediately the stone is not a genuine diamond.
•4 Weigh the stone against a confirmed diamond of the same carat. Diamonds weigh less than cubic zirconias, so if the two stones are real diamonds they will have roughly the same weight.