Out of 4Cs, Cut has the greatest influence on a diamond ’s beauty and sparkle. Diamond Cut specifically refers to the quality of a diamond’s brilliance, fire, scintillation, angles, proportions, symmetrical facets, and overall craftmanship. These factors directly impact a diamond’s ability to sparkle, along with its overall aesthetic appeal. Two diamonds may have the same clarity, color and carat weight, but cut is what determines whether or not one is superior to the other.
When a diamond is cut to ideal proportions, light will then reflect from one facet to another and disperse though the top of the stone, resulting in a display of brilliance and fire. Diamonds that are cut too deep or too shallow lose light, leading to less brilliance, fire, scintillation, and value. Even a diamond with a flawless clarity grade can look glassy or dull if the cut is too shallow or deep.
The significant traits of a well-cut diamond are its brilliance, fire and scintillation.
Brilliance relates to the intensity of the internal and external reflections of white light returned to the eye through the crown of a diamond.
Fire is the dispersion of white light into the colors of the rainbow.
Scintillation — also known as sparkle — is the flashes of reflective light emanating from a diamond’s polished facets which are observed when either the diamond or light source is moved.
Ideal cut diamonds
Ideal cut diamonds are those whose symmetry, angles, light reflection, proportions and shine are as perfect as gemstones can be. They offer the highest amount of fire and brilliance. Most of the light that enters the diamond is reflected through the table and crown, resulting in the spectacular sparkle. Hence, ideal cut diamonds are the top of the diamond line. They are the smallest percentage (roughly the top 3 %) of all perfect diamonds and the rarest of all. Ideal cut diamonds are usually produced in two brilliant cuts; round cut and princess cut.
Ideal / Excellent 1
This diamond with a uniform pattern of bright and dark areas is marked as Ideal or Excellent as it meets the standard circumstances of the top category for all grade levels.
Ideal / Excellent 2
Despite having different proportions from the ideal 1 diamond, this diamond has a uniform pattern of bright and dark areas and also meets the standard circumstances of the top category for all grade levels. So, this is considered as Ideal or Excellent cut.
Ideal/ Excellent 3
This diamond also meets the standard circumstances of the top category for
all grade levels. So, this can also be considered as Ideal or Excellent cut.
Very Good Cut Diamonds
Very Good Cut diamonds provide superior fire and brilliance. The diamonds of this grade have very symmetrical proportion and polish. Majority of light, nearly as much light as an ideal cut, is reflected back through the diamond. Only top 15% of diamond cut quality are Very Good Cut diamonds. They have very similar sparkle with the ideal/excellent cut diamonds, but are at lower price. Very Good Cut diamonds can be a perfect choice for you if they have high quality of the other Cs.
Very Good 1
This diamond is graded Very Good Cut because of its brightness, scintillation and final polish. Even though the individual proportion does not necessarily affect its brightness or scintillation, the overall proportion creates the darkness in pavilion main.
Very Good 2
This diamond is graded by its fire, scintillation and weight ratio. Its higher crown height and steeper crown angle cause its “splintery” pattern, along with long lower gridle-facets.
Very Good 3
This diamond’s grade is decided by its fire, scintillation and final finish. A slight darkness appears within the table and along the upper-girdle facet.
Good Cut Diamonds
Good cut diamonds are graded because they have more or less of standard cut grade characteristics than of ideal cut grade diamonds. They provide fire and brilliance, with much of light reflecting through the table. The diamonds of this grade have less symmetrical proportion, fire, brilliant and sparkle than those of Very Good Cut. The top 25% of diamond cut quality are Good Cut diamonds.
This diamond is graded by its scintillation. The slightly shallow pavilion angle causes darkness in pavilion main.
This diamond grade is decided by its fire, scintillation and weight ratio. A slightly steep crown, combined with steep pavilion and total depth produce dark ring in upper-girdle facet.
This diamond is graded Good Cut because of its brilliance. The shallow crown angle and low crown height make the darkness appear especially in the table area.
Fair or Poor Cut Diamonds
Fair cut diamonds are those which has little brilliance as only small amount of entering light reflects through the table while most of the light easily exits through the bottom and sides of the diamond.
Poor Cut diamonds have no sparkle, brilliance or fire at all. All the incoming light escapes through the sides and bottom of the diamond without reflecting.
These diamonds are graded Fair or Poor because of their too deep or too shallow depth. Diamonds from these low cut grade do not meet the standard of great cut quality at great value and often appear dull or glassy. 35% of the diamond cut quality represents Fair or Poor grade.
This diamond is graded Fair because of its scintillation. Its shallow crown angle and fairly shallow pavilion cause the overall appearance with a lack of contrast and darkness.
This diamond grade is decided by its fire, scintillation and weight ratio. It has somewhat steep crown angle, steep pavilion angle and long total depth. The combination of those imperfection leads to dullness with a very dark upper-griddle area and general darkness on the table surface.
This diamond is determined by its brightness and scintillation. Its large table, shallow crown height and slightly thick gridle cause darkness and a little of fisheye which is more noticeable when the diamond is tilted.
This diamond’s grade is limited by its weight ratio. Most of the proportions for this diamond are quite proportional, however, the extremely thick gridle make the weight increase hugely. So, this diamond’s diameter is much smaller than its carat weight would indicate.
This diamond’s grade is limited by its fire and scintillation. The combination of its somewhat steep crown angle, very deep pavilion angle and large total depth make the diamond’s table area and upper-gridle areas very dark.
Anatomy of a diamond
Table: The largest facet of a gemstone
Crown: The top portion of a diamond extending from the girdle to the table
Girdle: The intersection of the crown and pavilion which defines the circumference of a diamond
Diameter: The measurement from one girdle edge of a diamond straight across to the opposing side
Pavilion: The bottom portion of a diamond, extending from the girdle to the culet
Culet: The facet at the tip of a gemstone. The preferred culet is not visible with the unaided eye (graded “none” or “small”)
Depth: The height of a gemstone measured from the culet to the table.