AGS Gets Proportion-al

AGS may have done itself a disservice by describing their new “Gold Standard” grading system as only “proportion based” while calling their “Platinum Standard” AGS 0-10 system “performance based”. The reality is both of their systems are performance based, and use the same evaluation metrics to arrive at a different 6-level word grade instead of the 11-level numerical 0-10 grade. Calling one system proportion based and the other performance based is semantics originally used to imply the superiority of their “performance based” grading system to that of GIA's, which, for several reasons, including necessary averaging and rounding, AGS and others referred to as “proportion based”. The underlying truth is that both GIA's and AGSLAB's grading systems are both performance based. That is, they are based upon the three-dimensional (3-D) light performance resulting from the 3-D interaction of light with a diamond's proportions. This is in contrast to the old 2-D ray trace analysis of proportions done in the past by diamond cut investigators, the most celebrated of whom was Marcel Tolkowsky. His theoretical angles were developed from ray tracing using only a 2-D cross-sectional slice of the 3-D round brilliant cut diamond. Performance based means that the AGS system evaluates the 3-D light performance of a diamond to arrive at a grade, by raytracing a virtual model of its proportions obtained from a Sarin scan. This is compared to the GIA system, which takes the same proportions from the scan, judiciously averages them, and arrives at an estimated grade with their “performance based” system embodied in the “GIA Facetware”. Facetware contains “Cut Grade Reference Charts” and “Cut Grade Estimation Tables” which are published in GIA's Diamond Grading Lab Manual for use in cut grade estimation by gemologists, appraisers and cutters. These charts and tables are a simple method of communicating their grading system. This method of estimating a cut grade using look-up tables, which, through usage, has incorrectly come to be called proportion based, is winning the day for GIA because a diamond cutter can determine from them how to best optimize the cutting of a rough diamond crystal to get the best grade and yield. Seeing the GIA's success, and recognizing this need on the part of the cutters and others desiring the simplest way to understand their grading system, AGSLAB has developed and published their “Gold Standard” grading system with their own charts and tables. Lab director, Peter Yantzer feels this new system “is much easier to use, easier to understand, easier to teach and easier to explain. AGSLAB has developed with this Gold Standard, a mainstream way of communicating their grading system using the word rather than numeric terminology: Ideal, Excellent, Very Good, Good, Fair and Poor. Some craftsmanship issues not effecting light performance, such as polish grade have been relaxed. However, underlying this new Gold Standard is the same AGSLAB's performance based grading system. It is expressed and communicated with this simpler word scale with charts and tables similar to those successfully employed by GIA. Remember that underlying both GIA's grading system and AGSLAB's two grading systems are each laboratories' 3D light-performance based, grading metrics.

In reply to Jules " I advise AGS to work with GIA instead of against GIA ". Why work with a corrupt organisation that refuses to name the GIA bribers of the Certifigate scandal and does NOT guarantee their reports ? All these major labs vying for market share have to " reinvent the wheel " in order to compete but always risk their reputations doing so. I agree it's confusing. Both vendor and buyer are unprotected.Everyone seems to forget the two main purposes of a report are to verify if a diamond is natural or treated. Use your eyes when buying.It's that simple. NAME THE GIA BRIBERS Daniel Katz www.DiamondImports.com.au

Wow, How interesting. AGS, has once again reinvented the wheel. If AGS would just take the time to consider that they and they alone have always created the confusion by using a number system, instead of the world wide GIA system, it just might, penterate through that they are the ones confusing things for the customers. Using different nomenclature to mean the same thing as a world wide system to pass yourself off as an ELITE group, has caused many headaches in the industry and has created a schism to an industry already suffering from poor press. I advise AGS to work with GIA instead of against GIA.

Questioning whether the industry should move to a standardized cut grade, like we have for color and clarity, is ironic. While we have a standardized "nomenclature" for grading, which all of the labs use, there is nothing at all standard about its application.

Well, this is interesting - and confusing. If I read this right, AGS now sees what GIA saw... that consumers cannot distinguish between 10 different grades. Hence GIA's five grade Cut Grading Scale. But given an AGS "Ideal" being the equivalent to an old AGS Zero or One Cut Grade, and GIA's "Excellent" being roughly equivalent to an AGS "Ideal" - Zero and One Cut Grade, this puts AGS's "Excellent" equivalent to GIA's "Very Good", and so on, until somewhere they finally agree with each other - at Fair or Poor? I'm confused.