According to Kerry Folan for Racked.com, a diamond engagement ring can be analyzed for authenticity using several evaluations, such as the rainbow test, weight test, electric test, flawless test and magnifying test. These methods assess a diamond's unique qualities, including electrical conductivity, density, refractivity, visible flaws and crisp edges. An experienced jeweler can quickly inspect a stone and determine if it is an authentic diamond or a cubic zirconia substitute.
Debra Kelly from Knowledge Nuts suggests attempting to read a newspaper through the stone to determine if it is diamond or cubic zirconia. If letters are apparent through the stone, it is most likely cubic zirconia, because diamonds refract too much light to be able to see through them. Diamonds that are not flawless should also appear blue under a black light. If the stone is clear, it is either a rare perfect diamond or a cubic zirconia substitute.
As Kelly explains, cubic zirconia stones are flawless, extremely vibrant diamond look-alikes that many people mistake for the real thing. It is very difficult to identify differences between the two stones with the naked eye. However, cubic zirconia are not nearly as strong and scratch-resistant as diamonds are. It is highly uncommon to find any scrapes on the face of a diamond, so the presence of small cuts on the stone are telltale signs that it is fake, notes Kelly.