Beware of self-certification or certifications from less stringent local labs. These may be used by sellers to inflate their profits, as subtle differences in diamond grading can dramatically affect price. Remember, comparing diamonds with different certifications is misleading. Demand a recognized international certificate for diamonds larger than 0.30ct for an accurate and fair assessment.

To protect consumers, the five leading diamond certification organizations assign a unique number to each diamond they grade. This number is often laser-inscribed on the diamond's girdle, particularly on GIA certificates and some others, and can be easily verified with a magnifying glass. This ensures that the diamond you purchase is authentic and matches the information on its certificate.

Even among internationally recognized diamond certifications, discrepancies exist. The diamond industry often uses the Gemological Institute of America (GIA) as its benchmark due to its strict standards. Comparing a diamond certified by GIA to one graded by IGI or the more lenient EGL is not an apples-to-apples comparison. A diamond with a certain color or clarity grade on an EGL certificate might receive a 2-3 grade lower rating if evaluated by GIA. Therefore, diamonds with EGL certifications should be priced accordingly lower than GIA-certified diamonds with the same reported grades.