Objective Diamond Clarity Grading

The diamond clarity grading scale used worldwide today was introduced by the Gemological Institute of America (GIA) in 1953. To help address varying interpretations and inconsistencies in clarity grading between laboratories (and even within some labs), this article introduces an objective system for diamond clarity grading. The determination of the clarity grade is influenced by up to five factors: size, number, contrast (colour and relief), position and nature of the inclusions. The proposed system assesses these factors (with emphasis on the first four) by using an objective metric that emulates the intuitive analysis done by experienced diamond graders. Using high-quality photographs of more than 100 randomly selected diamond examples, this article demonstrates a high degree of agreement between clarity grades obtained using this system and those determined by GIA and the American Gem Society Laboratories (AGSL). The system’s objective methodology may offer a means for improving inter- and intra-laboratory grading consistency.

Click to download the pdf: Objective Diamond Clarity Grading – published in The Journal of Gemmology, 34(4), 2014, pp. 316–332, http://dx.doi.org/10.15506/JoG.2014.34.4.316

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Michael Cowing