1.If you have access to a diamond tester, you can test for diamonds vs. fakes. (Beware, moissanite can fool the electronic diamond testers.)
2.The transparency test. Turn your diamond upside down and place it over printed text. If you can clearly read through the stone, it’s not a diamond.
3.The fog test. Put your diamond in front of your mouth and fog it like you would fog a mirror. If it stays fogged for 2-4 seconds, it’s a fake. A real diamond will disperse the heat instantly so by the time you look at it, it has already cleared up.
4.Test for weight. The most popular fake is a cubic zirconia. C.Z.’s will weigh approximately 55% more than diamonds for the same shape and size. Use a carat or gram scale to see if the impostor tips the scales too much.
5.The U.V. test. Many diamonds will show fluorescence of blue if put under an ultra violet light or black light. 99% of all fakes don’t do this; so, a positive identification of medium to strong blue would indicate a diamond. Diamonds with blue fluorescence can be as much as 20% less valuable; however, lack of blue fluorescence doesn’t mean it’s a fake; it could be a better quality diamond.
6.The under the loop test. With a magnifying lens, there are some things you can look for on the stone that might give away its identity:
1.Look at your diamond from the top and see how the facets (the cuts on top of the diamond) are joined. They should be sharp but not rolled.
2.Is the girdle faceted or frosty (yes, then it’s a diamond) or waxy and slick (yes, then it’s a fake.)
3.Under magnification, look into your diamond for flaws (carbon, pinpoints, small cracks.) It’s very hard to put inclusions into a fake.
4.Look at the stamps inside the setting. A stamp of “14K, 18K, 750, 900, 950, PT, Plat” indicates the setting is real gold or platinum. This gives a better chance that the stone in it is real as well. Look for any “C.Z.” stamps. This will tell you the center stone is not a diamond.

A good rule of thumb in choosing a diamond jewelry appraiser is if you don’t know where to go to get jewelry appraised…read your local jewelry appraiser reviews. If you only choose one item, a diamond ring appraisal would probably be your best choice.  Also, if your purpose is to sell diamond jewelry, a current jewelry appraisal will help you decide a better selling price.