The difference between diamond “cut” and diamond “shape” is easy to understand, once it’s explained. The confusion comes up only because the word “cut” is used to refer both to the shape of a diamond and also to the quality of the cutting of the diamond.
Quick answer
Examples like “princess cut” and “cushion cut” really mean “princess shape” and “cushion shape.”
Examples like “ideal cut” or “good cut” or “excellent cut” in a GIA diamond certificate refer to how well or poorly the diamond was cut by the diamond cutter.
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Shape
Some examples of the industry’s use of “cut” to mean “shape” include:
- Round brilliant cut
- Princess cut
- Cushion cut
- Oval cut
- Pear shaped cut
- Marquise cut
- Emerald cut
- Asscher cut
- Radiant cut
- Heart-shaped cut
But cut in these examples just means “shape.”
Why does shape make a difference?
Shape is important because it has everything to do with first impressions of a diamond.
Shape determines how big a diamond looks. Some shapes are deep, so they will look smaller when viewed from above. A round brilliant shape is like that. Some shapes have more surface area on top. They will look larger. For example an emerald shape, Asscher shape, or marquise.
Shape also has a lot to do with the way the diamond plays with light. A round brilliant shape is the shape which creates the most sparkle. But an emerald shaped diamond is an example of a shape which creates the most clarity and luster.
Cut
The industry also uses “cut” to refer to how well the the diamond has been formed by the diamond cutter. Diamond cutters take raw gemstone and cut it with specialized tools. Like anything, this activity of cutting diamonds can be planned well, or planned poorly.
Also, even if the plan is perfect, the actual cutting can be done well, or be done poorly. So, the word “Cut” refers to how well a diamond was physically cut. Was it cut well or poorly?
Why does the quality of the cut make a difference?
The quality of the cut makes a huge difference because it has everything to do with how well a diamond treats light.
You already learned on this page that the round brilliant shape is the cut with the most sparkle.
But that assumes that whoever actually cut the diamond did their job well. What if the round brilliant shape diamond was cut all wrong. For example, the symmetry could be off. The diamond could have been cut too deeply (it is too tall). Or it could be cut too shallow (it would be too “short”). These mistakes would drastically affect how well the diamond played with light.
A good analogy is a dressing room mirror, the kind with three sides in which you can see yourself from every angle. If a mirror is “cut” badly — crooked, the mirrors not placed right, etc — then the reflection and your view of yourself in the mirror would be all wrong.
That’s why cut quality makes such a huge difference in engagement rings. One little mistake in the quality of cut can make the light inside the diamond behave wrongly, and go out of the sides, instead of up through the top.
Conclusion
And that’s the difference between “cut” and “shape” when it comes to diamonds. “Cut” can mean how well a diamond is cut. Or it can refer to the shape of a diamond.
Of course “shape” always refers to the shape. For example, “heart shaped,” “pear shaped,” and so on.
