How to tell if a Diamond is real

I found this info while Googling. I thought you might find it useful here too. Short of a jeweler's appraisal...
There are some less reliable methods you can try but there are no guarantees with these:
1. The old “If it will scratch glass it has to be a diamond.” Well, it is true that diamonds do scratch glass but so do a lot of the other fakes on the market. To boot, it’s possible to injure your rock even if it’s real during your hardness test.
2. The transparency test. If you flip the diamond in question upside down and place it over some newsprint and can clearly read through the stone, it’s not a diamond. (The problem with this test is some diamonds are cut shallow and can be read through.)
3. The fog test. This test I like a lot. Put the rock in front of your mouth and fog it like you would try to fog a mirror. If it stays fogged for 2-4 seconds, it’s a fake. A real diamond disperses the heat instantaneously so by the time you look at it, it has already cleared up. (A down fall to this test is oil and dirt on the stone can effect its 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 epoxied together.)
4. The weight test. The most popular of diamond simulants (fake) is a cubic zirconia. C.Z.’s weigh approximately 55% more than diamonds for the same shape and dimension. So if you have a carat or gram scale at your disposal you can see if the imposter tips the scales too much.
5. The U.V. test. A high percentage of diamonds fluorescence blue when put under an ultra violet light (black light). Since 99% of all fakes don’t, a positive identification of medium to strong blue would indicate a diamond. The bad news is if this method proves you have a diamond, it also proves your diamond is worth less. Diamonds with blue fluorescence are as much as 20% less valuable. Remember, lack of blue fluorescence doesn’t mean it’s a fake; it could just be a better quality diamond.
6. Under the loop test. If you own some sort of magnifying lens, there are some things you can look for on the stone that might give away its identity:

A. Look at the rock from the top and see how well the facets (cuts on top of the diamond) are joined. They should be sharp not rolled.
B. Look at the girdle and see if it is faceted or frosty (a clear sign it’s a diamond) or waxy and slick (an indication it’s a fake).
C. While you’re looking at your stone under magnification, look into your stone to see if you detect any flaws (carbon, pinpoints, small cracks). These are typically clear indications it’s the real thing since it’s very hard to put inclusions in a fake.
D. After examining the stone, focus in on 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 which gives a better chance that the stone in it is real as well. While you’re looking at the interior of the ring, also look for any "C.Z." stamps that would indicate the center stone is not a diamond.

Good info. I have a $99 diamond tester that works on the principle of thermal dissipation time curve...... and is usually 99% accurate.

The breath test works if the diamond is large enough

A jeweler will test it for you, most time for free. They use a hardness tester.

Check out this page too: [www.darasdiamonds.com] It is about diamond education. It teaches you things like diamond clarity, diamond color, diamond carat and diamond cuts.

I use this test, I give it to my wife , if she likes it, it's real and gets me out of the dog house and I live to detect another day

Hard to top caretaker but always remember found a 14 kt..16 diamond ring covered with mud...came home ran under cold water and from two rooms away my wife knew it was real.

Hard to believe but they are now putting fakers in 14kt. rings so only your jeweler knows for sure....