There are good diamont testers on the market that will tell you if you have a real diamond, an imitation or some other colorless gem. However, when buying diamonds from someone other than a certified retailer, most buyers will not know the difference between a diamond and an imitation. And if 'out in the field', it can be challenging to tell the difference. Below are fove (5)simple tests that may help.
See-through test - looking at the stone face up, if you can see through it, it's probably and imitation. The exception would be if a real diamond were poorly cut or the presence of dirt or grease allowed you to see through it. You can also try placing the stone face down over newsprint, if you can read the letters through the stone - again, probably imitation. Note, some diamonds set in antique jewelry will allow you to see through them due to the different cut (rose or mine cut) and the presence of the large culet (cut on the bottom parallel to the top of the stone)|
Rainbow test - move the stone under a light and note the flashes of rainbow colors compared to a diamond. If the colors are more obvious, chances are the stone may be synthetic; less obvious, the stone may be imitation.
Closed back test - When looking at jewelry set with diamonds, check the back. If the bottom of the stone is blocked or enclosed in metal it is probably imitation as most diamonds have at the very minimum the bottom partially viewable. However, an open back does not guarantee the stone is a diamond. Note: In antique jewelry prior to the eighteenth century, it was common to put a foil backing on diamonds to improve on their brilliance. Current styles where channel set diamonds are used, jewelers have used solid backs to increase the rigidity of the setting. |
Tilt test - Tilt the stone against a dark background and look for an obvious dark, fan shaped area. If you see such a fan, chances are the stone is imitation. This test is easier to perform on mounted stones and also works best on round cuts.
Price test - if the stone is being sold at an unbelievably low price - chances are it might be imitation, stolen - or maybe you just found the find of the century.
This is a very brief overview of testing for diamonds without use of a professional testing kit. For those that are seriously interested in diamonds, there's no substitute for experience. A good reference book to start with is The Diamond Ring Buying Guide by Renee Newman - available from this link.
And for who really want to be certain of what they are buying or have - we would recommend getting a diamond testing kit by Presidium - it positively will test stones as being authentically diamonds. We've had one for many years and it has proved invaluable.