When a so-called lot (a gemstone package with a specific number of diamonds) is through withthe cutting process, it is boiled, weighed, counted once again and it then goes to the grading-roomfor grading. In our plant, grading is done only by women. In our experience, women are moreconsistent graders than men.Depending on the grader’s state of mind, the grading is sometimes strict and sometimes notas strict. A diamond grader must obviously try to keep these mood swings at a minimum whenevaluating. The stones are first sieved. Small brilliants are not classified and sold as per theweight, but as per the sieve size.Thus, the following categories are customary ininternational trade:Sieve size- 6½ brilliants of 0.003 to 0.02 ct+ 6½ - 11 brilliants of 0.025 to 0.07 ct+ 11 - 14 brilliants of 0.075 to 0.135 ctWeight categories are used to classify stones ofsieve sizes larger than 14.After the sieving, the stones are first graded asper the colour and then as per the clarity.
In international trade, the colour of a diamondis stated using letters. At a national level however,depending on the selling country, use of all kinds of terms is possible.The Scandinavian nomenclature is used most commonly in Germany: River, Top Wesselton,Wesselton, Topcrystal, etc. Internationally, the best colour is D (River D), followed by E (RiverE), then F (Top Wesselton +), G (Top Wesselton), H (Wesselton) and so on. The letter seriescontinues up to Z, which represents a rather yellow colour. Yellower than Z would again be moreexpensive and would fall under the fancy yellow category.