RapNet Blog

The crystal structure of diamonds has a significant impact on what cut grade and more specific, polished grade could be achieved. Diamond surfaces are anisotropic, meaning that they have varying degrees of hardness. Some areas (crystal faces) can be cut and polished and others not. Diamond polishers have to know where to cut facets so as to avoid having any facets coinciding with such faces.

Understanding cut grades allows a retailer to make informed decisions when purchasing diamonds and therefore buy better. It also allows a retailer to explain the cut grade of a diamond to a client in an authoritative manner.

Grading laboratories have differing criteria for cut grades, however there is commonality in reporting as far as cut grading is concerned. There are three main factors determining the cut grade of a diamond, namely:

1. Proportions
2. Symmetry
3. Polish

Every facet on a diamond fulfills a specific function. The crown facets are the ‘windows’ of the diamond which let light enter and exit a diamond. The pavilion facets are the ‘work horses’ that reflect light back through the crown facets. It is important that facets be placed in the correct positions and on the correct angles to perform their task effectively. The crown and pavilion facets have to line up perfectly. Also, all the facets have to be polished, so that they are free of any polish lines, abrasions or other surface anomalies that could compromise light reflection. After all, any diamond is only as good as its worst facet.

One of the things we have discovered after serving the jewelry industry for many years through our dedicated diamond re-cut and repair service is that Princesses form a disproportionate percentage of repairs. It is also the most abused and butchered of all diamond shapes. Over the years I have seen it all. Out of center culets, misaligned girdles, no girdles, Great Wall of China girdles, steep and flat facet groups and diamonds proportionately compromised with weights that they had no right to. But that is not all.

Some years back my company received a ‘natural fancy yellow’ diamond which was a poorly cut cushion shape (to say the least). The request from our customer was that we re-cut this into a properly proportioned cushion. The copy of the grading report stated that it was a natural fancy yellow. I called our customer and informed him that the diamond does not have the body color of a fancy yellow. Before I agreed to start the work, the calls went back and forth, and with my last call I sounded the warning; 'this is an M color.' He replied; 'cut the diamond, I will fight them on the color; they have to honor their former report!'

There are a plethora of images on websites, and printed material to show the evils of flat or steep diamonds, but are they a correct rendering of what really happens to light in a diamond? Let us put them to the test.