(via Gem & Jewellery News, Vol. 11, No.4 September 2002) Harry Levy writes:
The International Standards Organization (ISO) papers on diamond grading harmonization have at last been published and been sent to the participating countries to be voted on.
If the vote is passed it means that the world will have an ISO standard for grading diamonds. If it is not passed, then the working group will have to reconvene and it is doubtful if another paper will be published in the near future. It has taken over fifteen years to have reached this stage. Some of those who were involved in the writing of these papers have indicated they will vote against it. How has this state of affairs arisen and how will it affect diamond grading and the diamond trade and all those involved in selling grading certificates with their stones?
Terms for color
Diamonds have been graded for many years for color and clarity. Initially descriptive terms for color, sometimes based on geographical locations, were used. For example, we had ‘white’, ‘tinted’, ‘cape’, ‘wesselton’, ‘river’, ‘light brown’ stones and so on. There was usually local understanding of these terms and how they would be used, but there were no universal agreements. So partners in a firm, local dealers belonging to a diamond bourse or those traveling to, say, South Africa, would understand what a ‘cape series’ was, but this was very much an esoteric language. ‘White’ meant different things to different dealers, and one could rarely buy on the seller’s description only, one had to see the stone. The prominent systems to be used were the ones used in South Africa as a producing country, and consisted of terms ‘wesselton, ‘crystal’, and ‘cape’, with words such as ‘top’ added as a prefix. End users adopted and modified such systems and the above terminology was incorporated into the Scan D N grading system.
A further system was introduced top make the language less esoteric and terms such as ‘white’, ‘tinted’, and ‘brown’ were used with prefixes such as ‘exceptional’, ‘rare’, ‘slightly’ and ‘top’ being used. As an aside, stones sold as ‘blue white’ and ‘premier’ are now referred to as those that have fluorescence.
GIA system
In all its confusion an attempt was made by the GIA to introduce a grading system which was more objective than the subjective methods used. They picked on a certain number of stones of different shades, graded these by comparing them to each other ranging from the purest white (or, more accurately, colorlessness) to shades of pale yellow, gave letters to these stones and referred to them as ‘Master Stones’. They called the highest grade a D color, and graded the rest down using E, F, G and so on. There was a perceivable shade of color between adjacent stones in this series. Thus, a stone which looked more colorless than a G but less colorless than an F, was referred to as an F color.
The letter D was taken to be the best color and this was done, according to the late Richard Liddicoat (for many years Chairman of the GIA), to void confusion with letters already in use such as A, B and C. The systems using these letters had been further modified by using A+, A++, AA, AAA, and so on. D was the failure grade in American schools and as an ‘in joke’ and, on the assumption that D had never been used to denote a color grade, they made this the top color. The trade and public found this to a far less confusing system—they knew the lower the letter the lower was the color.
Clarity terms
On the clarity grading terms such as ‘loupe clean’, ‘very very small inclusions’ (VVS), ‘very small inclusions’ (VS), ‘small inclusions’ (SI), were used and these too were easy to understand. With such a system in place investors discovered diamond as something worth putting their money into and so started the investment market and soon prices began to rise in leaps and bounds. Everyone wanted graded stones and certified diamonds and diamond reports appeared all over the place, with the result that the grading in some of the labs became less and less consistent.
Dangers for the trade
Bodies such as CIBJO saw the danger in this for the trade and tried to introduce some sort of control. They did this recognizing only a certain number of laboratories, the general rule being one per country and preferably recognized by national associations. They too introduced a system of grading diamonds using terms such as ‘white’ and ‘tinted’ as explained above. They had their own set of Master Stones for color grading. It was known that they had been co-operating with the GIA but it was unclear as to how the Master Stones had been obtained. The system they adopted was to give a chart linking their stones to the GIA system, thus ‘exceptional white +’ was D, ‘rare white’ a G and so on.
The main laboratory in Antwerp was the HRD and they too had evolved their own system again using descriptive terms such as ‘white’ with their own sets of master stones. They became the main laboratory in Antwerp serving the diamond industry there through the International Diamond Council (IDC).
Thus in the mid-eighties we had several acceptable systems in operation and the diamond trade, through the encouragement of groups such as the Diamond Trading Company, thought that all those systems should be harmonized. In this way the now international diamond trade would become truly international with all countries speaking the same language in grading diamonds.
ISO Standard drafted
The main groups got together and decided to draw up an ISO Standard. These groups were the GIA, IDC, CIBJO and Scan DN. The standard was to be drafted in two parts, Part 1 to deal with Terminology and Classification. This defined how terms such as those referring to the type of inclusions within a diamond should be used and the color grades, as well as defining different shapes of diamonds. This was ISO/FDIS 11211-1. Part 2 would deal with Test Methods, explaining under what conditions color should be determined, how various measurements would be made and how these would be shown on a report. The points here are of course more numerous than I am stating in this article, but the combined papers should enable a laboratory to grade and produce a report on a diamond and all those using the Standard would produce more or less identical reports.
It was around the time of completion of Part 1 that one of the main participants decided to drop out. This was the GIA. As one who was not involved with the actual working group it is difficult to know exactly why this occurred. Maybe the GIA, considering themselves leaders in the field of diamond grading could see no point in giving their system away to be used by everyone as it was possible that many laboratories using GIA terminology would not necessarily grade to their standards.
Importance of cut
This left Scan DN, CIBJO and IDC in the working group. As I have often said in these articles there is far more in determining the price of a diamond than merely color and clarity. In considering the 4 Cs—carat, clarity, color and cut—most people forget about the cut and it is this that gives the stone its beauty. All grading reports indicate the size of the table and the depth of a stone as a percentage of its width or diameter, but it takes an expert to interpret this.
The IDC indicates the depths of the crown and the pavilion separately and then gives a comment on the proportions of the stones using terms such as ‘good’, ‘very good’ and ‘unusual’. The GIA does not give these comments on proportion but makes general judgments on the symmetry of a stone. This difference led to a compromise being reached two years ago that a proportion comment would be optional.
When the papers were finally published and circulated the IDC claimed that they had understood that proportion comment would be mandatory on all grading reports.
If the IDC wishes are accepted then there are those who feel that the GIA system would fall short of the Standard in that they do not comment on proportion. There are also those countries who have used the GIA system over the years and would not like to see s Standard that somewhat denigrates the system they have used for years and could confuse their public. At the time of writing the vote has not been completed so the result is awaited with interest.
No comments:
Post a Comment