A 2020 Review of the ICSL Coloured Stones Grading System
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.