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Brillanteering


cbailey
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This may be a little hard to explain but I’ll give it a shot.

 

For starters, brillianteering is a verb. It refers to the process by which the cutter adds the outside row of facets on both the crown and pavilion. These are respectively known as the upper girdle and lower girdle facets. Every facet has an angle relative to the girdle plane and an azmuth, which is the rotation or twist of the facet when compared to the center vertical axis of the stone. In a mathematically perfect stone, these facets are all placed at exactly the same angles (upper girdle at one angle, lower girdle at another) and the azmuth will be exactly aligned with an imaginary line that runs perpendicular to the girdle through the center of the table and culet. In the real world, the cutter makes each facet individually and they can control both the angle and the azimuth as they make it if they wish. This can lead to variations that affect the optics of the stone but that aren’t reflected in the numbers on the grading report. These variations are collectively known as non-standard brillianteering. The crown angle is the average of the 8 crown mains, the pavilion angle is the average angle of the 8 pavilion mains. That leaves 32 facets that aren’t described on the lab report at all!

 

Is non-standard brillianteering bad? That depends. Cutters will use unusual brillianteering for a variety of reasons. In some cases they can make a stone a little heavier this way. That drives up the price they can get from a particular piece of rough by compromising on the optics. More money - less beauty. Shoppers with sense would call that bad and this is the reason that GIA dings the cut grade for it. Sometimes there is an inclusion that they want to cut out and they can improve the clarity by a little bit of tweaking here. Better clarity, not much affect on weight. Maybe good, maybe bad depending on whether it worked and what it does to the optics. Sometimes they are looking for a particular optical effect, like the hearts & arrows pattern, that can be enhanced by careful brillianteering. If you're into h&a (I rather like it but not everyone does), that's good. It can also be used to maximize some specific measured results on some of the tools that graders use like idealscopes, brilliancescopes and the like.

 

One of my favorite stones in my collection is an AGS-0/GIA very good. The reason GIA downgraded it is the unusual brillianteering. In the case of that stone, I love it, as do most of my customers when I show it to them. I actually paid extra to get it. In other cases I agree with GIA that it detracts from the stone. I realize that this isn’t the good/bad answer that you were expecting but sometimes the world just doesn’t work that way.

 

Tha fact that you like it is a good sign. That's the effect you're going for after all. Have you seen it or are you basing your preference on how it looks in a list of numbers for superficially similar stones?

 

Neil

Edited by denverappraiser
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