Fake or Real Diamond?

Buying a diamond for the first time is a very personal and exciting experience. Hands down, the first thing on the mind of the buyer will be: How can I know I am buying the real thing and not a fake?

If you have been given a beautiful diamond or heirloom and you want to be absolutely sure that your diamond is real, get a professional appraisal. This can be done by looking under "Jewelry" (Appraisal) found in your yellow pages. Call to inquire about their services and ask these two important questions:

1. Will I be able to accompany my jewelry at all times or will you take my jewelry to evaluate elsewhere? If they say they will need to separate your jewelry from you at any point, it would be wise to find another appraiser.
2. What is the fee? ($50.00-$75.00 is considered a good fee.)

If a professional appraisal is not within your limited budget, here are some other methods.

1. If you have access to a diamond tester, you can test for diamonds vs. simulants. (Beware, moissanite is the only stone than can fool the electronic diamond tester.)
2. The transparency test. Flip your diamond upside down and place it over some newsprint. If you can clearly read through the stone, it's not a diamond. (Beware, some low cut diamonds or stones such as emeralds can be read through.)
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 instantaneously so by the time you look at it, it has already cleared up. Oil and dirt on the stone can affect reliability and the test is not accurate at all on doublets where the top of the stone is diamond and the bottom is cubic zirconia glued together.
4. Test for weight. The most popular diamond simulant (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 "10K, 14K, 18K, 585, 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.

source: http://www.nationaljewelerssupplies.com/diamonds-real-or-fake.html