Can You Ever Cut the Gem Crown First?
Yes, on some designs, you can cut the crown first successfully. However, cutting the crown first is more likely to result in wasted gem rough. You’re also taking a greater risk that your finished stone won’t perform well. Nevertheless, for many designs, cutting the crown first just won’t work.
The biggest exception to cutting the pavilion first is during faceting competitions. Some faceters cut the crown first to get the table and star facets dead on. Judges inspect those difficult-to-cut areas closely. Keep in mind that competition cutters are usually very experienced, and competition stones are usually cut from common natural rough or something synthetic of no great value.
The Pavilion is the Light Engine of the Gemstone
There are several reasons why you should cut the pavilion first. Most importantly, the pavilion functions as the main light reflector for a faceted gem. In terms of a gem’s optical display, the pavilion does the majority of the work. If you don’t cut the pavilion facets at the proper angles, the entire stone will lose performance. The gem will have less brightness or brilliance.
The Most Commonly Faceted Materials Leave Little Room for Error
The critical angles and sweet spots for gem performance have a narrow range, especially in materials with a low refractive index (RI). With so little room for error, any changes to the pavilion angles can dramatically alter a design’s performance.
Take a look at the RIs of the most commonly faceted natural gemstones:
- Quartz (1.544-1.553)
- Oregon Sunstone (1.559-1.573)
- Beryl (1.562-1.602)
- Topaz (1.609-1.643)
- Tourmaline (1.614-1.666)
- Peridot (1.650-1.703)
- Spinel (1.712-1.762)
- Garnet (1.72-1.95)
- Sapphire (1.762-1.778)
- Zircon (1.810 to 2.024)
I would call RIs from 1.54 to 1.67 low-range. Note how many commonly cut natural stones fall within that range. This means cutting the pavilion angles properly is critical for those gemstones. For example, 41º is a pretty standard angle for pavilion mains in quartz. This generally gives quartz gems the best performance. Practically speaking, these angles can’t vary more than a degree or so. If they do, the gem’s light return is usually changed for the worse.
What does this have to do with cutting pavilions first? Basically, since the pavilion tiers require very specific angles in order to reflect light, faceters have limited options when it comes to cutting a design.
Pavilions Set Up the Rest of the Gemstone
Beyond just cutting a gem design, faceters must also accommodate the condition of the natural rough. I find cutting the pavilion first very helpful when dealing with the flaws natural rough may have. After cutting the pavilion angles properly, I know the shape of the stone and where everything else will line up.
From a faceting standpoint, cutting the pavilion first makes the rest of the stone take care of itself. Once the pavilion is cut, the girdle and crown depth and placements are quite easy to line up. Basically, the pavilion sets the rest of the stone. On the other hand, if you cut the crown first, you’re just guessing at the pavilion and girdle depth needed to finish the stone.
Cutting the Crown First Means Cutting the Hard Way
Let’s look at quartz again. If you cut the crown first, you can calculate the depth needed for the design’s pavilion. However, you’re assuming everything will work perfectly with the gemstone. How often does that happen?
If you encounter any problems cutting the pavilion, you can’t deviate much from that 41º angle for the pavilion main tier without negatively affecting the performance. So, if you come up short in depth when you cut the pavilion, you can’t just adjust the angles and hope the design works.
Some faceters who cut crown first try to solve this problem by leaving extra room to cut the pavilion. However, this creates another problem. If you’re leaving extra room for the pavilion, you’re likely going to waste more gem material. Of course, if you’re cutting lab-made rough or something very cheap, maybe the waste isn’t really significant. But what if you’re cutting more valuable material?
Low-Symmetry Designs Need to be Cut Pavilion First
Many gem designs require you to cut the pavilion first in order to establish the stone’s shape and outline. This applies to most low-symmetry designs. Barions, rectangles, ovals, hearts, marquises, and many other shapes need the pavilion cut first to establish the girdle. For example, cutting an OMNI Barion isn’t really possible, and certainly not practical, unless you cut the pavilion first.
For many designs, you can’t cut the crown to center point. Even if you do find a design that calls for cutting the crown to center point, you’ll still waste gem rough to do it. After all, you’ll have to grind off the center point to make a table sooner or later. Low-symmetry designs are especially difficult to cut crown first evenly to center point.
The Crown is More Forgiving Than the Pavilion
Crown facets can influence where light that enters the gem through the crown hits the pavilion facets. However, the influence is minimal, particularly in low-RI material. The shape and number of crown facets themselves don’t really make much difference to the light entering the stone, but they can help make patterns within the gems. For example, take a look at my “Mirage Cuts,” like the Texas Mirage and the Floating Lilly. That’s one of the principles I based them on. The patterns on the gems are just illusions, not facets themselves.
What is important to the gem design are the angles of the crown facets. That being said, the crown angles aren’t nearly as critical as the pavilion angles. You can usually vary the crown angles far more than the pavilion angles. This may affect the stone’s look significantly but, within a certain range, not dramatically. For example, the standard crown angles for quartz generally range from 28º to 42º. As you can see, a wide range will work. In contrast, change the pavilion angles by as little as one degree and you could kill the gem’s performance.
What does this mean for gem cutting? It just makes sense to cut the pavilion first since you can’t really change it. However, you can make adjustments to the crown as needed in the later stages of faceting.
Stick to the Gem Design
Although you have more flexibility when cutting the crown, if you choose a gem design because of how it looks, whether in a photo or a ray trace, cut it as published. If you deviate from the crown facet angles the designer intended, you’ll still affect the way the finished stone looks. Usually, you’ll lower the stone’s performance and appearance.