The Gem Lab

Coloured Stone Grading

A full coloured stone report takes all the characteristics of the stone in to account to reach a final grade that relates to price. We are one of the few laboratories in the world that offer this service. We offer a passport size report which includes a picture of the gemstone. For credit card size reports on coloured stones we suggest the mini coloured stone report.

The details of the gemstones for the full reports contain the following information:
Reference number, gemstone species and variety, weight, cut / shape, dimensions, colour description, colour grade, tone, clarity grade, brilliance, finish, final grade and an image.

For the mini report, the following information is included:
Reference number, gemstone variety, weight, cut/shape, dimensions, colour description, clarity and finish.

We use the ICSL coloured stone grading system, which has proved itself to be the most efficient and user-friendly coloured stone grading system since 1982. Many large laboratories around the world use this system. It is the most consistent system I have ever come across. Ian Campbell who developed the system introduced the FINAL GRADE which relates directly to price. For more information on this system, please see below.

Example: Coloured Stone Passport

If you would like your stone/s graded, please call us:

The Gem Lab: +27 21 761 1746

Example: Coloured Stone Passport

If you would like your stone/s graded, please call us:

The Gem Lab: +27 21 761 1746

Special Note:
The Gem Lab coloured stone reports are not a glamourised ‘selling document’. There are no fancy names given to over-insinuate grades. Therefore it can be considered neutral in this context to both buyers and sellers alike. Only those who market over-enhanced graded stones will be unhappy with this situation.

The ICSL (Independent Coloured Stone Laboratory) Grading System

All coloured stones are graded according to the ICSL system as it applies to all gemstones.

The ICSL system was designed to give unbiased professional opinions by qualified gemmologists of the quality of cut gemstones after strictly taking into account the carefully constructed parameters essentially used in the process. It also gives realistic reports in plain English without stating misleading nomenclature that is so often seen these days.

Some large laboratories use the ICSL grading system but generalise the terminology which can cover 3 or 4 grades.

A Brief Outline of How the ICSL Grading System Works

Numerals (100-0 based) are coincidently used. The reasons are two-fold: for computer database applications, and to give an overall comparative perspective (overview) of grades. A carefully designed scale of deductions also allows a stable final quality grade to be assessed – without this it cannot be systematically done.

We start off by grading the colour and then deducting points for characteristics that take away the beauty of the stone.

For example, we would deduct as follows to reach a final grade which relates to price:

Let’s take an emerald with a good colour which is moderately included affecting the overall brilliance of the stone. Keep in mind this is a very simple example of how the system works.

We look at other characteristics as well which can affect the final grade, such as Tone, Proportions, Symmetry, Finish, Transparency, Dichroism, Colour Distribution, Zoning (Colour), Treatments etc.

Deductions
Colour Grade8080 (Very good)
Clarity Grade50-10
Brilliance40-10
Final Grade60(Moderately Good)

Final Grade

The ICSL system was the FIRST laboratory internationally to give FINAL GRADES, which were in turn based on the of all the other component parameters. The nomenclature ‘Final Grade’ was introduced by ICSL in 1982. Only after the ICSL Coloured Stones Grading System was first published in 1985 in the USA, did the first laboratory, in New York, follow suit. However, this was under the guise of different nomenclature.

A Quick Way To Interpret The Significance Of The Final Quality Grade

One has to look only at the difference, if it exists, between the Colour Grade and the Final (quality) Grade. If there is a downward shift numerically between them, for example ICSL 80 (Very Good) to ICSL 70 (Good), this will immediately have the effect of informing the reader that the stone has been down-graded because of a number of faults that exist. If no faults exist to within the (practical) defined limits, the final grade will not change from the colour grade. In the example given above this would remain as ICSL 80 (Very Good). A stone’s colour grade (and this can vary with the species) dictates its maximum possible final grade. The only exceptions are phenomenon-type stones (such as star ruby or sapphire, to name only two). It is important to use suitable colour comparison stones or other compatible means for assessing the colour grade, provided such are used correctly and consistently.

This Gemstone Identification and Grading Course is available online at our Academy of Gemmology.

This course will also show you how to price the gemstone once graded.

Gemstone Grading Course

A 2026 Review of the ICSL Coloured Stones Grading System

Developed by Ian Campbell FGA
Revised by Jeremy Rothon FGA

ICSL is the acronym for ‘Independent Coloured Stones Laboratory’.

The gem trade in South Africa has been the recipient of many ICSL coloured stones grading certificates/reports over a very long period of time. In recent years this demand has increased considerably. It is therefore appropriate that a review be given of this system so that a wider spectrum of users are better informed about it.

Short History

The ICSL system was introduced to the trade in 1982 by the Independent Coloured Stones Laboratory. It has been a successful and reliable medium for the quality grading of coloured gemstones for over a quarter century and has successfully withstood the test of time.

It was originally published in 1985 by the Accredited Gemologists Association in the USA. Only slight rationalization has taken place since then because of the system’s proven stability. At that time it was openly presented to a relatively large number of professional gemmologists and their associates in the USA. The report-back was very good and there was no known criticism made. This was considered very significant because it was aired in the presence of one’s peers. A certificate, was awarded for this.

The ICSL system was designed to give unbiased professional opinions by qualified gemmologists of the quality of cut gemstones after strictly taking into account the carefully constructed parameters essentially used in the process. It also gives realistic reports in plain English without stating misleading nomenclature that is so often seen these days.

Numerals (100-0 based) are coincidently used. The reasons are two-fold: for computer database applications, and to give an overall comparative perspective (overview) of grades. A carefully designed scale of deductions also allows a stable final quality grade to be assessed – without this it cannot be systematically done.

The ICSL system was the FIRST laboratory internationally to give FINAL GRADES, which were in turn based on the analysis of all the other component parameters. The nomenclature ‘FINAL GRADE’ was introduced by ICSL in 1982. Only after the ICSL Coloured Stones Grading System was first published in 1985 in the USA, did the first laboratory, in New York, follow suit. However, this was under the guise of different nomenclature.

Usage of the ICSL Grading System Reports

Some very few traders and laboratories that use the ICSL based reports do not want ANY derogatory remarks entered on their documents. This could normally be considered as misleading and does not say much in favour of this practice. However, the ICSL system is so designed as to allow this tolerance to be adopted, BUT ONLY UP TO A POINT. It is important to know that whether this is done or not, the FINAL (quality) grade is ALWAYS, without exception, reduced as a penalty for whatever is wrong with the stone. This is adequately covered in the terms of reference of the system. The recipient still receives the correct grade.

Therefore, this descriptive omission, on a limited basis, is allowable only because it is, by default, taken fully into account in the report in any case. Properly used, the system is scrupulously fair to all concerned.

A Quick Way to Interpret the Significance of the Final Quality Grade

One has to look only at the difference, if it exists, between the Colour Grade and the Final (quality) Grade. If there is a downward shift numerically between them, for example ICSL 80 (Very Good) to ICSL 70 (Good), this will immediately have the effect of informing the reader that the stone has been down-graded because of a number of faults that exist. If no faults exist to within the (practical) defined limits, the final grade will not change from the colour grade. In the example given above this would remain as ICSL 80 (Very Good). A stone’s colour grade (and this can vary with the species) dictates its maximum possible final grade.

The only exceptions are phenomenon-type stones (such as star ruby or sapphire, to name only two). It is important to use suitable colour comparison stones or other compatible means for assessing the colour grade, provided such are used correctly and consistently.

Copyright

In spite of the copyright nature of this grading system, the Independent Coloured Stones Laboratory and The Gem Lab confirms that there is no legal problem to be encountered by those seriously using and thus recognizing the ICSL system, subject to only two conditions:

  1. The grading is done correctly within the FULL terms reference of the ICSL system.
  2. The relevant documents acknowledge use of the ICSL system. (Simple endorsement: ‘Based on ICSL grading parameters’).

The usage of the ICSL system is encouraged, because it has an established history, is well conceived and sets a good standard for the quality assessment of cut gems. If you would like more information on the ICSL system contact me on info@gemlab.co.za.

Questionable Grading Systems

Notwithstanding what is written above, numerous so-called grading systems that have made an appearance in South Africa in comparatively recent times use nomenclature which indicates over-enhanced qualities at almost all significant pro-rata levels on the recognized quality scale. Looking at the prevalence of such, one could even wonder if there are any poorer quality stones left in the market place! Tanzanite in particular is subject to this type of over representation. This type of over-grading is a worrying trend and should not be encouraged. The term so-called used in the above paragraph is because proper terms of reference cannot be found for such ‘systems’. Purely descriptive names relating to grades are all very well, but supporting parameters should be properly defined if they are to relate to a meaningful system. Definitions are very important in this context, in that they afford reasonable stability on an on-going basis.

Worst of all are what could be termed quasi-systems. These show parameters that really do not make much sense, other than to glorify a stone to an absurd degree of high quality. As an actual example, one such parameter relates to clarity grading (of tanzanite in this case), which goes beyond the state of ‘Flawless’ to become described as ‘Flawless +’. How flawless can a stone get?

There are also other similar type overdone grades that parallel this – not only in that particular grading process, but others as well, where highly suggestive alphabetical letters are very misleading to the uninitiated buyer in the way they are presented in the reports.

This leads to an opinion that this sort of thing constitutes an enhanced ‘selling’ certificate or report, whereby a prospective customer is lulled into a false sense of having bought a stone of unusually good quality, when in fact it is well below that status. Such misrepresentation, in the opinion of this writer, does a disservice to both the customer as well as the image of the gem trade, no matter where that happens to be. It is this type of anomalous service that stretches credibility to the limit in the case of meaningful documentation in this context.