other then a testor here are some quick ways to tell if a diamond is real or fake
Cubic Zirconia's are usually made of glass, but they can sparkle and shine almost as much as a real diamond can. What they can't do, however, is scratch glass. One of the most important keys to distinguishing between a real diamond and a fake one is to perform the "Scratch Test". A real diamond will scratch glass, ruby, sapphire, and even Cubic Zirconia. This is because, on the Moh's Scale, real diamonds have a hardness rating of "ten". They give them the distinction of being the hardest natural mineral known to man. Cubic Zirconia only has a rating of "eight and a half" on the Moh's Scale. It can also be scratched by a ruby or a sapphire.
Another way you can tell if a diamond is real or a fake is to give it a "Fog Test". Hold the diamond up to your mouth and breathe on it as if you were going to clean it. Then, immediately look at it and see if the fog has quickly dissipated or not. If it did, then chances are the stone is real. If the fog stays on the stone longer than a few seconds, it may well be a Cubic Zirconia.
If you hold a real diamond under a black light, it will give off a blue look. Since most of the Cubic Zirconia look - alikes don't, this could be yet another way to tell if it's real or not. Or, if you look at a diamond under a high - powered magnifying glass, you should look for tiny, thin cracks or other flaws. If the stone has them, it could well be the "real McCoy"because it's impossible to implant these typed of imperfections in a fake diamond.
i higly recomond the magnifying glass and the black light combined
Mav