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Cut - Diamond Education - NYG Laboratory Resources
Diamond Cut
Diamond Cut
Cut is a diamond's most important characteristic. It determines what we generally think of as sparkle.
The beauty of a diamond depends more on cut than any other factor. The extent of how well the diamond is cut is directly related to the diamond’s overall beauty.
A good cut gives a diamond its brilliance, which is the brightness that seems to come from the very center of a diamond.
The cut of a diamond refers not to its shape, but to the balance of proportion, symmetry and polish achieved by the diamond cutter.
The angles and finish of any diamond are what determine its ability to handle light, which affects the brilliance.
When a diamond has been correctly cut, the diamond’s ability to reflect and refract light is greatly enhanced.
When a diamond is well-cut, light will enter through the table and travel to the pavilion where it will reflect the light from one side to the other before reflecting back out of the diamond through the table.
If it is too shallow, the light will be lost out the sides causing the diamond to lose brilliance. If it is too deep, the light escapes out the bottom causing the diamond to appear dark and dull.
When a diamond is fashioned from a rough stone, the cutter must balance optimal cut (and therefore appearance) against maximum yield (cutting the diamond to maintain as much carat weight from the rough stone as possible).
This is why the Cut grade is so important; it allows the purchaser to identify those stones that were cut Fair to Poor in an effort to gain carat weight.
By understanding the way that light moves through diamond crystals, modern diamond cutters have established a specific set of proportions and angles that are known to harness the diamond’s internal brilliance and to show it in its best light.
Cut Image
Light Reflection
Light Reflection Effects To Estimate Cut Type
How Light Reflects From A Diamond?
Diamonds are renowned for their ability to transmit light and sparkle so intensely.
The quality of cut is determined by how well the symmetry, polish, and proportions of the diamond produce the most attractive balance of the three different types of reflection.
Several proportion factors have the most immediate impact on a diamond's ability to reflect light correctly.
We often think of a diamond's cut as shape (round, emerald, pear), but a diamond's cut grade is really about how well a diamond's facets interact with light.
The table size and depth of a diamond relative to the diameter greatly impacts the light return from a diamond.
When light strikes a diamond, approximately 20% immediately reflects off the surface (as glare). Of the 80% that enters, a portion will escape through the bottom of the diamond (where the observer cannot appreciate it).
A well-cut diamond is proportioned so that most of the light entering the gem exits back through the top of the stone, perfectly balancing the white light (brilliance) with intense flashes of fire (dispersion).
A poorly-cut diamond, with facets cut only a few degrees out of alignment, can result in light exiting through the bottom of the diamond, known as light leakage, instead of from the top where it is visible.
This creates a diamond with dulled brilliance from poor light performance within the gem, making the center of the gem look dark.
The best cut diamonds have proportions that are within tried and true ranges known for maximizing brilliance, fire, and scintillation.
A well proportioned diamond will have each facet properly placed and angled so as to maximize the amount of light that reflects back out of the crown (top) of the diamond, to the eye of the observer.
This reflected light is perceived as scintillation, fire and brilliance.
When light meets any facet of a diamond, it will either reflect (bounce back) or refract (bend while passing through the facet).
The angle that the light hits the facet determines whether the majority of light reflects or refracts, which is why cut is so important.
Diamond Characteristics
Main Characteristics of Diamond Used To Reflect Lights

Crown : The top portion of the diamond, from the girdle to the table.
Pavilion : The lower portion of a diamond, from the girdle to the culet.
Culet : The facet or point on the bottom of the diamond's pavilion.
Girdle : The narrow rim around the widest part of a diamond, separating the crown from the pavillion. Also referred to as the setting edge, where a diamond is held when set in jewelry.
Depth : The height of a gemstone, from the culet to the table. Determined as a percentage of the overall diameter of the gem.
Table : Calculated by dividing the width of the table facet by the width of the diamond.
Ttypes of Reflection:
Three Different Types of Reflection
Brilliance : Brilliance, or brightness, refers to the white light that is reflected back to the eye from the diamond. Light enters through the top of the diamond (the table), is broken down into a rainbow of spectral colors, and is reflected back and forth in the interior of the gem by bouncing off the mirror-like facets. Light exits through the table, recombining as white light.

Dispersion (Fire) : Dispersion is the rainbow of colors that is reflected back to the eye from the diamond.
Light enters through the top of the diamond, is broken down into a rainbow of spectral colors, and is reflected back and forth in the interior of the gem by bouncing off the mirror-like facets.
When it leaves through the crown, it stays separated and reaches the eye in flashes of color.

Scintillation : Scintillation is the play of light you see with movement of the diamond, demonstrated by sparkling on the diamond’s surface.
A diamond is evaluated on its ability to reflect and refract light in all directions.
Types of Cut
Diamond Cut
Different Cut of Diamond
Super Ideal Cut : Cut to the most exacting standards. On the diamond certificate, graded as "Excellent" or "Ideal" for cut, polish, and symmetry. These diamonds will also show a "hearts and arrows" facet pattern, have the most desirable girdle and culet dimensions. It proportioned to return the maximum possible light.
Ideal Cut : Represents roughly the top 3% of diamond quality based on cut. Exquisite quality cut to create the optimal combination of brilliance and fire. Reflects nearly all light that enters the diamond. A exquisite and rare cut.
Very Good Cut : Represents roughly the top 15% of diamond quality based on cut. Superior quality cut that reflects nearly as much light as the ideal cut, but for a lower price.
Good Cut : Represents roughly the top 25% of diamond quality based on cut. Premium quality cut to optimize the size without sacrificing quality or beauty. Reflects most light that enters.
Fair Cut : Represents roughly the top 35% of diamond quality based on cut. Adequate quality cut which reflects some light while maximizing weight. While not as brilliant as a good cut, still a quality diamond.
Poor Cut : Inadequate quality cut that reflects minimal amount of light. Brilliant Earth does not provide diamonds with cut grades of poor.
Other Cut
Other Diamond Cut
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