When you shop for a diamond, the most advertised factors which affect its value are the “4 C’s” carat weight, cut, (proportions, not shape), color and clarity.  Don’t forget another important factor, cost.  In order to understand the complexity of the diamond grading system, you should consult with a diamond expert, preferably a graduate gemologist, who has earned the highest degree offered by the Gemological Institute of America (GIA), or Accredited Jewelry Professional (AJP.)  

• Shop for an un-mounted diamond. A diamond that has been set in a ring may have imperfections that are hidden behind the ring’s prongs. 
• Ask to see several diamonds within your price range and compare their characteristics. 
• Insist each diamond is accompanied by a grading report preferably from GIA. GIA Diamond Grading Reports are the most widely used reports in the industry and grade only unmounted diamonds. GIA offers laboratory grading services to the trade and the public. 
• GIA Laboratory can also laser-inscribe the diamond’s report number on the diamond so the diamond can be identified if it is ever lost or stolen. 
• To locate a diamond expert near you, visit www.gia.edu.
• Diamond clarity is an indication of a diamond’s purity.
•  An internally flawless diamond is extremely rare and costly. Therefore, it is wise to have each diamond inspected to determine the type of flaw it contains and how it may weaken the stone (if it breaks the stone’s surface) or obstructs the refraction of light through the stone.
• Look for the retail jeweler’s refund policy. The Virginia Consumer Protection Act requires that it must be conspicuously posted. The refund policy should give you sufficient time to take the diamond for an insurance appraisal (the diamond should appraise higher than the price you paid) to an independent appraiser/graduate gemologist (not another retailer who may have a vested interest in selling you another diamond).  If the retailer does not permit refunds, go to another jeweler.    
• Never leave your new diamond to be set in a ring or leave the ring for repairs or cleaning unless you are given an intake receipt which contains the retailer’s name and address, date, your name and address and a complete description of the stone and value of the ring. When you receive the ring back, take it (with your independent appraisal or GIA Report) to your selling jeweler or independent appraiser to verify that the stone matches the reports.  Some jewelers have been known to switch diamonds with cubic zirconia.   
• If you buy a diamond online, print out the web pages that detail the transaction, including the site’s return policy.