How to Examine a Diamond

To accurately judge the quality of a diamond, it is advisable to use more than the naked eye.It is much harder than judging a Rolex watch. Here are common ways to examine a diamond.
Microscope/Loop: To examine inclusions, one uses either a microscope or a 10x magnifying glass called a jeweler's loop. This enables one to see inclusions in stones. Most dealers will let you use theirs.
Diamond Tester: A diamond tester uses light to verify that the stone you are examining is really a diamond. It does not guarantee quality -- just the type of stone. Most testers will still work when the stone is mounted. Jewelry Mall Diamond Tester Search Results
Certification: If you are unsure of your diamond knowledge or the jeweler you are buying from, get a certified Diamond. The best known and reliable certification is from GIA (Gemological Institute of America) or EGL (European Gemological Laboratory). Be aware that certificates will cost you an extra $100-$200 on average.
Also there are some diamonds on the watches,such as Rolex Daytona,Rolex Datejust,Rolex Day-Date,Richard Mille,Porsche Design and Breitling,you can also examine the diamonds using the ways below.