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Princess/Emerald Cut Grading

 The Princess and Emerald/Radiant Cut grading system used in Gemology Tools was developed by the National Association of Jewelry Appraisers.

The Princess and Emerald/Radiant Diamond Cut Grading module works the same way as the Round Diamond Cut Grading module. Open the Princess and Emerald/Radiant Cut Grader by selecting the shape from the Cut Grading menu at the top of the program (i.e. Princess or Emerald/Radiant etc).

Grading a Princess Cut:

Enter your measurement data  in millimeters (length, width and depth).

In the Table field you have the option of entering the data in millimeters or percentage of width. Double click in the Table field to toggle between the two options. Example: you have a stone width of 6.4 mm's and a table width of 3.74 mm's (which equals a table of 60%). If entering MM's you would enter 3.74 and the program will automatically convert it to the percentage for you. If entering % you would enter 60.

Crown Height Percentage:  Be aware that for Princess and Emerald/Radiant cuts NAJA asks for Crown Height Percentage (not the usual Crown Angle). Therefore, the F7 key (Crown Angle Calculator) has been disabled. However, in the Crown Height % field you have the option of entering the data in millimeters or crown height percentage. Double click in the Crown Height % field to toggle between the two options. Example: you have a stone width of 6.4 mm's and a crown height of .8 mm's (which equals a crown height percentage of .125 which we then multiply by 100 for a 12.5% crown height figure). If entering MM's you would enter .8. If entering % you would enter 12.5.

Girdle Thickness:
  There are several ways to enter the girdle thickness information.  If your diamond has a thickness which is relatively the same all the way around the stone you can select the appropriate term (i.e. Medium). 
 
Range:  Most diamonds have a range of girdle thickness terms (i.e. Slightly Thin to Thick).  If this is the case select Range from the Girdle Thickness list box.  You will be asked to enter narrowest and widest thickness’ of the girdle.  You also must enter the Overall percentage (this isn’t important unless you want the comparison, but you must enter a number.  If don’t want to compare then enter the number 4).  Click OK.

User Defined: If you want to change the default girdle thickness percentage for your term (Medium defaults to 3.2%) you should select User Defined.  When you select User Defined you are asked first for the percentage and then the term.  The girdle percentage is really only important if you want to use the overall depth percentage figured by the program to compare with your depth percentage.  This is great way to verify that the numbers you enter make sense.

Why do we give a default figure of 3.2% for the medium girdle thickness when everyone knows that 1.7% is the ideal thickness for a medium girdle?  The reason is because the part of the girdle used in proportion grading is the WIDEST part of the scallop, whereas when we were taught to estimate girdle thickness by sight we were told to view the narrowest part of the scallop.  When you use the Proportion Scope to grade proportions, you put the diamond into the unit with a main bezel facet facing directly toward you.  This gives you a clear view of the crown angle on either side of the diamond's outline.  This outline is also of the widest part of the scallop, which is the part of the girdle that contributes to the total depth of the diamond.

Grading an Emerald Cut:

Make sure the Radiant box (in the upper right corner)doesn't have a check. This is important because you won't get a proper grade if you are grading an Emerald cut and the box is checked (the program will grade for a Radiant Cut if the box is checked).

Enter your measurement data  in millimeters (length, width and depth). For the table you have the option of entering the data in millimeters or percentage of width. Double click in the Table field to toggle between the two options.

Caution:  Be aware that for Princess and Emerald/Radiant cuts NAJA asks for Crown Height Percentage (not the usual Crown Angle). Therefore, the F7 (Crown Angle Calculator key) has been disabled.

Girdle Thickness: There are several ways to enter the girdle thickness information.  If your diamond has a thickness which is relatively the same all the way around the stone you can select the appropriate term (i.e. Medium). 
 
Range: Most diamonds have a range of girdle thickness terms (i.e. Slightly Thin to Thick).  If this is the case select Range from the Girdle Thickness list box.  You will be asked to enter narrowest and widest thickness’ of the girdle.  You also must enter the Overall percentage (this isn’t important unless you want the comparison, but you must enter a number.  If don’t want to compare then enter the number 4).  Click OK.

User Defined: If you want to change the default girdle thickness percentage for your term (Medium defaults to 3.2%) you should select User Defined.  When you select User Defined you are asked first for the percentage and then the term.  The girdle percentage is really only important if you want to use the overall depth percentage figured by the program to compare with your depth percentage.  This is great way to verify that the numbers you enter make sense.

Why do we give a default figure of 3.2% for the medium girdle thickness when everyone knows that 1.7% is the ideal thickness for a medium girdle?  The reason is because the part of the girdle used in proportion grading is the WIDEST part of the scallop, whereas when we were taught to estimate girdle thickness by sight we were told to view the narrowest part of the scallop.  When you use the Proportion Scope to grade proportions, you put the diamond into the unit with a main bezel facet facing directly toward you.  This gives you a clear view of the crown angle on either side of the diamond's outline.  This outline is also of the widest part of the scallop, which is the part of the girdle that contributes to the total depth of the diamond.

Grading a Radiant Cut:

Check the Radiant box in the upper right corner. This is important because you won't get a proper grade if you are grading a Radiant cut and the box isn't checked (the program assumes Emerald Cut if the box isn't checked).



Enter your measurement data  in millimeters (length, width and depth). For the table you have the option of entering the data in millimeters or percentage of width. Double click in the Table field to toggle between the two options.

Caution:  Be aware that for Princess and Emerald/Radiant cuts NAJA asks for Crown Height Percentage (not the usual Crown Angle). Therefore, the F7 (Crown Angle Calculator key) has been disabled. In the above example the sample Radiant Cut has a crown height percentage of 12.5%. Enter only the number (in this case 12.5).

Select your Girdle Thickness and Polish/Symmetry and press F2 or click the Grade button to view the final NAJA cut grade screen.

See Also: Round Diamond Cut Grading

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