All About Diamond Grading
Article By Admin
Feb 11, 2019
When buying a diamond, the most important assurance is that it should come with a certificate by an internationally recognized gemological authority. It is a form of validation by trained professionals in the field, of the quality of your diamond. Leading authorities includes the Gemological Institute of America (GIA), American Gemological Society (AGS) and International Gemological Institute (IGI). That being said, is one better than another?
Key Gemlogical Laboratories
GIA is one of the foremost gemological authority in the world. Established in 1931, it has entrenched itself as a key player in the field of diamond grading. The convention of 4Cs of diamond grading was developed by GIA and it has since been a gold standard in diamond grading. AGS was established in 1934, initially to cater to the United States domestic jewelry market, serving as a market standard. It soon expanded and is one of the key institutes worldwide. They utilize their own numeric scale of diamond grading, based on the grading standard developed by GIA. IGI was established in 1975 in Antwerp, the diamond capital of the world. Since then it has stood against the well-established institutes like GIA and AGS, who had accumulated 40 odd years of followings.
Research from an Empirical Perspective
Joseph Lee from Diamond Screener took an empirical approach to compare the certification standards of the gemological institutions, using dual certified diamonds (GIA and IGI) from inventories of Blue Nile and James Allen.
The study is based on 29 dual certified stones, and the grading of cut and color was analysed, yielding 58 comparisons. 32 comparison showed same grading standards, while GIA was stricter on 11 occasions and IGI was stricter on 15 occasions. Of these occurrence of differences in grading, the differences were a single unit apart, which was an acceptable deviation, with the exception of two comparison. One of which was GIA grading color of the diamond as ‘I’, while IGI graded it a ‘G’, two units apart. Both grades falls under the ‘near-colorless’ band. On the other occasion, GIA graded the clarity of a diamond as ‘VVS1’, while IGI graded it as ‘VS1’. The conclusion that can be drawn is that the grading was consistent between the two gemological laboratories and difference were mainly one unit apart (except for two comparisons).
Research from an Experimental Perspective
Another study came from Rapaport group, a network of companies providing value added service supporting fair and transparent diamond and jewelry market. They compared grading standards on six grading labs. To conduct the study, they sent 10 diamonds to six grading labs worldwide. With the grading report, they normalized the results on a ‘quality index’, whereby the lower the number the less lenient they are. Results showed that GIA was the strictest (at 14.8), with IGI trailing behind by one basis point (14.9). Median was at 15.9, while the ceiling was at 19.8.
Apart from that, the diamonds’ pricing was extrapolated from similar diamonds with similar quality on the Rapnet database. Data showed that GIA would yield the most revenue (i.e. being sold at the highest price), while revenue for IGI would rank fourth. This showed that while grading are consistent with GIA, their pricing are significantly lower than what the quality would deserve. This highlights a discounts for the consumers that cost are borne by the jewelers.
In conclusion, while diamond grading could be a somewhat subjective field, these variation do not stray much among these laboratories. The analysis of multitudes of grades of gems have only made the standards more consistent. In fact, these gemological institutes have only made buying a diamond more transparent than ever.