What Is Diamond Cut and Why Does It Matter?
Shape is the outline. Cut is the craft. Only one of the two decides whether a diamond looks alive.
Quick Answer
Diamond cut describes how a rough diamond has been shaped and faceted, including its proportions, symmetry and finish. It is different from diamond shape. A round diamond is a shape, while cut describes how that diamond has been fashioned. Cut matters because it affects how light moves through the diamond and therefore has a major influence on brightness, fire and scintillation.
Key Takeaways
- Cut and shape are not the same thing.
- Cut affects how a diamond interacts with light.
- Proportions, symmetry and polish are important parts of cut quality.
- A higher carat weight does not make up for a poor cut.
- Cut grades are not presented in exactly the same way for every diamond shape.
Cut vs Shape
This is one of the first things to understand.
Shape is the outline of the diamond.
Examples include round, oval, cushion, emerald, radiant, pear and heart.
Cut is about how the diamond has been fashioned.
It includes the arrangement and proportions of the facets and the quality of the finished stone.
So an oval diamond has a shape. Its cut describes how that oval was actually fashioned.
Why Does Cut Matter?
A diamond interacts with light through its facets.
When the proportions and facet arrangement work well together, light can be reflected back toward the viewer in a way that creates brightness and other visual effects.
A poorly proportioned diamond can allow more light to escape through areas where you do not want it to. That can make the stone look darker or less lively.
The Three Main Visual Effects
People often use the word "sparkle" to describe several different effects.
Brightness
The amount of white light returned from the diamond.
Fire
The flashes of spectral colour that can appear when light is dispersed.
Scintillation
The flashes of light and dark that appear as the diamond, viewer or light source moves.
Cut has a strong influence on all three.
What Goes Into Cut Quality?
Cut quality is not one single measurement.
It involves factors such as:
- Proportions
- Facet arrangement
- Symmetry
- Polish
- Overall finish
For round brilliant diamonds, laboratories such as GIA provide an overall cut grade. GIA currently does not give an overall cut grade to fancy shapes such as oval, cushion, emerald or radiant because their facet patterns and light behaviour vary more widely. Other laboratories may assess fancy shapes using their own systems. Regardless of shape, polish, symmetry, proportions and the actual light performance still matter.
Can You Tell if a Diamond Has a Good Cut?
The grading report is useful, but look at the actual diamond too.
A report can give you measurements and grades. Your eyes can tell you how the finished stone performs in real light.
When viewing a diamond, look for:
- Overall brightness
- Even light return
- Good contrast
- A lively appearance
- A balanced shape
If possible, view it under more than one lighting condition.
Does Cut Matter More Than Carat?
Carat and cut answer different questions.
Carat tells you how much the diamond weighs. Cut tells you how it has been fashioned.
A heavier diamond is not automatically more attractive.
If two stones are similar in carat, a better-cut diamond can look more lively and appealing.
What About Fancy Shapes?
Fancy shapes such as oval, cushion, emerald and radiant do not behave exactly like round brilliant diamonds.
Some have different facet patterns and different ways of handling light.
For example, an emerald cut is known for its broad, open facets and hall-of-mirrors effect rather than the same type of sparkle associated with a round brilliant.
Aureva’s Perspective
When someone says they want a "sparkly" diamond, we think the conversation should quickly move to cut. Size catches your attention first, but cut is a big part of what makes the diamond enjoyable to look at. It is worth taking a little time to understand it before deciding how much carat weight you want.
Frequently Asked Questions
Is cut the same as shape?
No. Shape describes the outline of the diamond. Cut describes how the diamond has been fashioned and how its facets interact with light.
Is an excellent cut diamond always the best?
A strong cut grade is useful, but you should still look at the individual diamond, its proportions, shape and appearance.
Does cut affect diamond sparkle?
Yes. Cut has a major effect on how a diamond interacts with light and therefore on its brightness, fire and scintillation.
Does cut matter for lab-grown diamonds?
Yes. Lab-grown diamonds can also have different cut qualities, and cut affects their visual performance in the same way it does for natural diamonds.
Sources
About the Author
The Aureva Editorial Team
The Aureva editorial team writes the Journal. We work with lab-grown diamonds and 14KT gold every day, and we write about what we can verify, such as grading reports, growth methods, and what we see across our own orders.
