Figure 1: Classic Shape of Rough Diamond
From Rough to Polished
The shape of a classic piece of diamond rough is called an “octahedron.” Imagine two 4-sided pyramids stuck together at their bases. Typically, that piece of rough is sawed into two pieces which are each then made into polished diamonds. Since diamonds jump in price exponentially with increased weight (well,not exactly, but see here for an explanation of diamond pricing), it makes more economic sense to saw that octahedron not down the middle, but just off center. Then the center of that piece of rough becomes the girdle of the larger polished diamond. (see Figure 2)
Different Diamond Cuts (Shapes) – Different Yields
Don’t worry, there’s a reason why I’m boring you with all these details. Take a look at Figure 2. Try to imagine what the rough looks like after it’s been sawed through the plane represented by the black line. What diamond cut (shape) does it look like? If you guessed Princess cut, you’d be correct. A princess cut is really just a slightly faceted sawed diamond crystal. It was invented not for its beauty, but in order to minimize loss of diamond material. A Princess cut can easily have a yield percentage of rough of 80-90% Compare this with a round diamond (represented by the purple diamond in Figure 3) that will at best have a yield percentage of rough of about 40%.
Rough Shape Informs Polished Shape
For diamond crystals with less than perfectly formed corners, the cutter might choose a radiant cut or asscher cut. For diamond crystals that are slightly more rectangular, the diamond cutter will choose a rectangular shape, such as an Emerald cut.
Some naturally occurring diamond crystals look like flat triangles. That’s how the Trillion, Heart shape, and Pear Shape diamonds were born.
Figure 2: 1 Piece of Rough = 2 Polished Diamonds
Anyway, you get the idea. With the exception of the Round Brilliant Cut, all the others were created to maximize polishing yield in different naturally occurring crystal formations.
In terms of popularity, Round Brilliant Cuts are by far the most popular shape. After rounds, princess cuts are the most popular. After princess, the numbers drop pretty steeply. I found this interesting chart at Jogia Diamond’s blog. They accumulated this data through their diamond search feature on their website. The proportions are for diamonds searched, not diamonds sold.
 |
HI
Please tell me if this an ideal cut oval diamond with no bow tie effect.
Depth 63.6
Table 55
Measurements
10.62by7.62by4.85
Is it ok to buy a diamond where the cert states additional clouds not shown. pinpoints not shown
Many thanks
There is absolutely no way to tell if an oval has a bow-tie without seeing it (or a high quality photo). The vast majority of ovals have them.
Just bought diamond ring emerald cut which is EGL certified ,why do you say this is wrong for a dealer to state this.
EGL is not a legitimate certificate. That is the issue. Here is our article on EGL for a full explanation.
Hello- can you tell me if this is a good diamond?
GIA Report: 5121214859
Carat Weight: 1.86 carat
MM: 9.92X8.4X3.77
Color: F
Clarity: VS1
Cut Very Good
Depth: 38%
Table: 69%
Girdle:TN-MD
Culet: None
Polish: VG
Symmetry:VG
Fluorescence: Strong Blue
Price: $11,892
No it is not. Never buy a colorless diamond with strong fluorescence.
Hello-I was wondering if you could assist with a trillion stone with the following specs:
Certified by EGLISR
1.58 CTW
Color E
Calrity Vs2
Lenght 9.07 mm
Width 8.24 mm
Depth 3.86 mm
Depth 42.6%
Table 65%
Polish/Symmetry VG
Flurorescence N
Price for stone- 12,800
Stay away. There is nothing more despicable than a dealer/jeweler selling a diamond with an EGL certificate (especially EGL Israel).
Thank you- I contacted James Allen to see any trillion cut but they indicated they don’t. Any suggestions where I could find a reputable dealer/jeweler online to work with? Also- what specifications would be best to look for a trillion as I am searching?
Jaime, send me an email through the contact us button.
Trying to find more information on rose cut diamonds. Are they valued less than other diamonds?
They are not a typical shape. No one cuts them except niche cutters who like selling odd shapes. We only focus on diamonds that are common. To be honest, we wouldn’t know much about rose cuts.