Around 1960, the GIA (Gemological Institute of America) developed the first laboratory grading reports to identify diamonds and report on some features of their quality. This followed the original system developed in Europe by DeBeers decades earlier. This also marked the beginning of the growth of the laboratory report industry. Those involved believed that some day many diamonds would be sold with reports issued by laboratories that were independent of the selling process.

In 2016 there are many such laboratories, each issuing their own version of a diamond grading report. The reports issued by the GIA and the American Gem Society (AGS) laboratories are considered to be the most accurate in the industry. For our customers we use and recommend reports issued only by these two laboratories.

There are several laboratories outside of the GIA and the AGS that claim to be using the GIA-AGS systems. But when their diamonds are re-graded using the GIA system, the final grades are often different, usually lower than their claim. This is because each laboratory may interpret differently identical grading language, causing many diamonds to be incorrectly graded and misrepresented at the time of the sale.

When clients bring in diamonds with other grading reports, they are examined to determine their grades under the GIA-AGS systems. Those grades are then compared to those stated on the customer’s report.

Laboratory reports of all kinds are here to stay. In fact, with diamonds of certain sizes and values, they are required by some homeowner’s insurance policies. Here are the questions you should always ask about laboratory grading reports:

  • If the report is not from the GIA or AGS, what grading scales are used and what do the grades mean in reference to the GIA grading system?
  • What features of the diamond are not described by the report? How do those features affect price?
  • Does the report provide a grade for the cut of the diamond? How is that grade established? What is the meaning of the grade compared to the systems designed by the GIA & AGS?
  • Was the report issued fairly recently? If not, has anything happened to the diamond since the report was issued?
  • Does the report contain any cost information? The best laboratories do not comment on cost of the gemstones they examine. Jewelers who use lab reports with values are attempting to create an appraised value that differs from their selling price. The gap between the two is used by buyers to judge “the deal.”


Don’t rely solely on the laboratory report to fully guarantee the quality of the diamond you purchase. Review the plot of the diamond’s flaws with your jeweler. Have the flaws explained. Ask if they affect the durability of the stone. Ask if the flaws block or distort light traveling through the diamond. Ask if flaws that are usually invisible suddenly become visible to the naked eye when the diamond’s pavilion is not clean.

Review with your jeweler the angles and proportions of the diamond and the amount of light that explodes from the top of the stone. This information is often hard to interpret from even very fine lab reports.

You are purchasing a diamond from your jeweler who should be your diamond expert, and the report is merely a written statement of corroboration that is useful to your insurance company. It is the jeweler’s knowledge that should create the necessary credibility to complete the purchase, not that of any faraway laboratory which has nothing to do with your satisfaction or happiness with your diamond.

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