1. The words we use
2. Three different cut grading approaches
3. Parametrical Approach
4. Direct Light or Optical Measurements
5. Proposed Three Dimensional Modeling Method
6. Implementation: Lessons from Other Markets and Industries
7. Conclusion

We all agree that the Diamond Industry needs constant growth and development, but are some of the key marketing concepts we use still useful?

- "A Diamond is Forever" does it lead to commoditization: "A Diamond is a Diamond"
- We all say (including Labs) "the round brilliant is best"
- "Ideal Cut" implies that everything else is less than "ideal"

The global consequences of using such concepts contribute to the commoditization of diamonds. If value adding decreases, there is an increasing risk of instability.
We would like to propose a way to develop a solution for the cut part of this problem by designing a system that gives equal rights of cut evaluation for all cuts. We believe this would be a useful tool that will lead to effective diversification. Our discussion will also consider grading systems used in other industries.

1. Parametrical
2. Direct light measurements
3. 3D diamond model

As shown in fig. 1 we believe all parametrical proportion based approaches could be considered as lying on a continuum beginning with a "few parameters" and progressing to "all parameters". We know that restricting consideration to only a few unrelated parameters (such as Table, Crown and Pavilion) is an improper method, but the consideration of all possible parameters and their inter-relationships is just not possible. This leads to the conclusion that parametrical approaches can not be successful in cut grading for round diamonds, let alone for fancy shapes.

Figure 1. Parametrical Approach

Parametric systems have some uses in the planning of cutting, but are incapable of leading to the systematic development of new cuts.
The problems with the current parametrical approach in the field of symmetry grading are shown in the left hand side on the chart below. A solution to symmetry grading that we will propose and based on precise 3D diamond modeling is shown on the right hand side of this chart:

See also "How symmetry affects diamond appearance: mutual relationship between diamond proportions and symmetry".

Figure 2. Stones like the one on left that shows very little leakage will be favored by the Ideal-Scope, over the stone on the right that shows more fire and scintillation.

Optical imaging or measurements may be produced by the means of equipment like Brilliancescope, Firescope, Hearts and Arrows Viewer, Idealscope, and Isse-2. However these grading systems suffer from poor perceptions of integrity because each system favors certain types of stones or the features of such stones. An example is shown in fig. 2. Some stones that look good or bad to our eyes may be graded differently by direct methods.

The principle problems of the direct approach:

• All structure lighting systems that rely on the human eye for interpretation will have different results depending on observer perception (in particular in different dynamic range and adaptation conditions);
• Devices that measure light and evaluate a diamonds light responses attempt to give an objective result for the subjective way human eyes and the brain perceive diamonds;
• We are unaware of current devices that can analyze a diamond through a range of tilting, or use many small (distant) light sources, to correctly estimate scintillation;
• Optical methods can not be used effectively to develop new cuts;
• All known approaches use a single view point. Humans have two eyes.

Sergey Sivovolenko, OctoNus, Moscow, Russia
Yuri Shelementiev, Gemological Center MSU, Moscow, Russia