Gram Princess: Online Faceting Designs and Diagrams
You can find cutting instructions for the Gram Princess here.
Very often, my customers ask me for princess-cut gems. Originally designed for shallow diamond rough, this cut made it possible for faceters to use odd bits of material. Unfortunately, the princess cut for diamonds doesn’t work well with the lower refractive indices (RIs) of colored gemstones. So, I decided to redo the entire cut for colored gems.
Please note that I made quite a few changes and recalculations to the original cut. I wanted to get a design that would cut well in colored material but still have the overall feel of a princess cut. However, the original princess design concept isn’t mine. I want to make that clear.
You can cut the Gram Princess in RIs 1.62 to 1.93 with no changes. If you want to cut this in quartz (70%), just add 2° to all of the pavilion tiers. No changes on the crown. On any of the higher RI materials, you can also raise the crown 4 to 6° without changing the light return much.
Changing the angle of the C3 tier by a degree or so, up or down, will change the overall size of the table quite a bit. It’s a good trick to use if your stone needs a little more or less area when you’re cutting it.
Although the Gram Princess isn’t especially hard to cut, the meets on the corners of the pavilion are tight. You could cut through them easily.
Notes on the Ray Trace
Here’s something else that might interest you. Look at the ray trace at the bottom of this article. Notice the dark areas in the four corners of the design? These areas are actually trapping light rays. This explains why they look dark in the ray trace. The ray trace loses track of them and doesn’t count them in the brightness figure. (At least, I don’t think it does).
Now, look at the photos of the cut stone. See anything interesting? These areas are actually returning light. In fact, their color looks a little more intense than the rest of the stone’s. That’s because of the trapped light rays.
The light ray trace is a good indication of the overall look of a stone. However, it’s not perfect. I’ve noticed this phenomenon in other gem designs I’ve published, but the Gram Princess and these pictures really illustrate this well.
Enjoy cutting your Gram Princess.
Detailed faceting instructions by Jeff Graham available at The Rock Peddler