New GIA and AGSL Naming Conventions For Cushion Cut Diamonds
Since October 2009 The Gemological Institute of America (GIA) has attempted to clarify and reorganize its naming of cushion cut diamonds to leave less room for interpretation and inconsistency from one grader to the next. The American Gem Society Laboratories (AGSL) has also made similar efforts to enhance the consistency of its naming conventions to follow the lead of GIA. It is my hope that both labs will strictly adhere to these recently developed changes and that exceptions will be much less prevalent moving forward.
History and Pre October 2009 GIA Naming Conventions
Robert Shipley, GIA’s founder described the traditional round brilliant as having 58 facets. Any deviation from that in number or shape of facets he referred to as modified or a variation of the round brilliant. More recently there have been similar debates about Cushion Brilliants. This has evolved over a number of years with different variations being cut and polished. In most cases the pavilions of the diamonds have been modified, similar to what Shipley described decades ago. The purpose may be the intention of creating a unique style, to retain more weight from the rough or to improve the appearance in some way. During this period GIA’s cutting style descriptions were challenged as more and more variations were created. Some were rather dramatic clearly resulting in a description of a “Cushion Modified Brilliant.”
Other variations were more subtle, usually with “kite” shape facets being added on the pavilion or half-moon shaped facets being added just below the girdle usually in some symmetrical form. In an effort to “split hairs” GIA’s descriptive system became confusing to apply and extremely difficult for the public to understand when a faceting style differed from the generally accepted description of the word “modified’. Using Shipley’s and other’s more traditional definitions, the GIA Laboratory has revised its naming convention when “modified” is used in a cutting style description.
Despite its use by the trade, GIA has not used the term Old Mine Cut or Old Mine Cushion on grading reports in at least twenty years. An Old Mine Cut is a term applied properly to an early form of brilliant cut which was most common in the 18th century with nearly square or cushion shaped girdle outline. A term applied occasionally and incorrectly to a somewhat more modern style of brilliant cut that also has a much higher crown, smaller table than the modern brilliant cut but whose model outline is circular or approximately circular in a style of cutting that is more properly called a Lumpy Stone or an Old European Cut.1
Current GIA Naming Conventions
Cushion Brilliant - Describes a stone with a rectangular or square outline, with rounded corners and rounded sides, with facets which are similar to the facet arrangement of a round brilliant cut, but could have more or less, consisting of a table facet, girdle plain, bezel extending from the table to the girdle plain, and pavilion mains extending from the culet to the girdle plain. Contains star facets, lower half facets, upper half facets, and may or may not have a culet facet. The following plots contain the most common types of cushion brilliants1:
Old Mine Brilliant - A traditional term used to describe an early form of the 58-facet Brilliant Cut with a nearly square or cushion shape girdle outline, a high crown, a small table, deep pavilion, and a large culet. These are a distinct style from the modern proportion sets seen today of the same 58-facet arrangement Cushion Brilliant.
As a general guideline, three out of four criteria must be true for it to be called Old Mine Brilliant instead of a Cushion Brilliant.
i) Table equal to or less than 53%
ii) Culet equal to or larger than slightly large
iii) Average Crown Angles of the Centre Bezels (across the width) are equal to or greater than 40 degrees
iv) Lower Half Length Equal to or Smaller than 60% (by visual inspection only)
The guideline for using this term has long been made by graders based on the facet arrangement and the diamond’s visual appearance. While the criteria developed in more recent years (above) accounts for a vast majority of older-style stones, there are exceptions where these parameters are close but the table is not as small or pavilion is not as deep. In these rare cases, the stones still possess the typical appearance of the older-cut stones. Currently GIA has no plans to discontinue the use of this traditional description and will still call stones containing the Cushion Brilliant facet structure by this traditional name. GIA is in the process of reevaluating the given criteria considering both traditional proportion sets and definitions as well as trade-use of this term.1
The inclusion plot diagrams used by GIA represent the basic shape outline and facet arrangement. They do not create diagrams to represent differing proportions of the actual stone (length to width ratio, lower half lengths, table size, culet size, etc.).
Cushion Modified Brilliant - To be called modified the facets have to be systematically added deleted or modified usually on the pavilion altering the brilliant cutting style. Some examples are shown below1:
Current AGSL Naming Conventions
The AGSL maintains a more trade friendly stance towards the naming of cushions with their ultimate goal to provide a consistent naming system understandable by both trade and consumer. Efforts will be made to follow the new more strict criteria set forth by GIA so that compatibility is achieved between the two laboratories. The AGSL does not use traditional names to describe modern reproductions of older cuttings styles, preferring to call all recently cut stones with Cushion outlines as either Cushion Brilliant or Cushion Modified Brilliant.
The inclusion diagrams found on AGS reports are based on a 3D Sarin scan matched as closely as possible to templates found in their extensive database. While the inclusion plots printed on their reports are not a direct print of this 3D scan, they are designed to accurately represent the relative facet size proportions and arrangements in a precise manner. New variations of facet structure can be readily added to their database when encountered. 2
The inclusion diagram below was taken from an AGS report of a common vintage Cushion Brilliant cutting style. The diagram reflects the four major and four minor pavilion main facets that extend from the culet to the girdle plain. In contrast GIA would have used the standardized diagram found in the Old Mine Brilliant section to identify inclusions in the same stone which would not have accurately reflected the different relative sizes of the pavilion mains.
Summary of Current GIA Naming Conventions:
1) GIA reports for cushions will use only the terms Cushion Brilliant and Cushion Modified Brilliant. The only exception to this is when the 58-facet Cushion Brilliant meets the older-style proportion criteria to change the naming from Cushion Brilliant to the more traditional Old Mine Brilliant.
2) The number of bezel or main facets does not determine whether the diamond will be named Cushion Brilliant or Cushion Modified Brilliant. Cushion Brilliants may have more or less than 58 total facets but must include a table facet, a girdle plane, bezels extending from the table to the girdle plane, pavilion mains extending from the culet to the girdle plane, star facets, lower half facets, upper half facets, and possibly a culet facet.
3) When the brilliant cutting style is altered whereby facets are symmetrically added, deleted or modified the shape is described as Cushion Modified Brilliant (e.g. split bezels, split stars, added triangular facets on sides). This modification can occur in either the crown or pavilion facets and either or both would result in the outline being called modified.
4) The inclusion plots printed on GIA reports are not scans of the actual diamond and may differ from the actual facet structure particularly in the shape and relative proportions of the pavilion facets. These plots are only the closest match to the limited number of diagrams found in the GIA database of over 600 digital diagrams. Plotted diagrams are intended to show the location, type, and relative size of inclusions in the diamond for clarity purposes only.
Summary of Current AGSL Naming Conventions:
1) Diamonds with a cushion outline will be described using the trade terms Cushion Brilliant and Cushion Modified Brilliant utilizing the same criteria as GIA for each.
2) AGS does not use the traditional term Old Mine Brilliant and will only use the term Old Mine Cut on their grading reports if the appearance truly fits that of an older cut stone from the appropriate time period.
3) The inclusion diagrams on AGSL reports while not an actual 3D plot illustrate the relative facet size proportions and arrangement allowing for accurate identification and comparison of facet structures.
Quick Reference Chart
References
1) Private Communications with GIA.
2) Private Communication with Peter Yantzer, Executive Director, American Gem Society Laboratories.
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