Cut grade is a quantitative measurement of the overall brilliance and scintillation of diamonds, as it has supreme effect on a diamond’s lighting performance. Cut grade is also determined by the table size, crown angle, depth, girdle thickness and polishing results of diamonds, which in turn affects the final appearance,and relationship with light and luster of diamonds.
(Please go to http://gia4cs.gia.edu/EN-US/the-diamond-4-cs.htm for more information about 4Cs by
Gemological Institute of America)
Anatomy of Diamond Vocabulary
Before learning about how does cutting influence the light shining through, we should know more about the common terms used:
- The facet at the top on diamond (always the largest facet)
- The measurement from table to culet
- The facet at the bottom (always the smallest facet)
- The upper side of diamond (measured from table to girdle)
- The lower side of diamond (measured from gride to culet)
- The edge distinguish the crown and the pavilion of diamond
Know more about cut
Cut is the dominating factor influencing the interaction of light with diamonds. Every diamond has its exclusive cutting, which leads to its unique brilliance and appearance. Thus, an Excellent cut diamond is considered to be the most valuable and scarcity.
If a diamond is too shallow, lights will escape from bottom of diamond, leading a lack of brilliance. If a diamond is too deep, light will spread out from the pavilion sides; the reflection of light will hence be poor and it will reduce the overall brilliance.
In order to have a best reflection, a symmetrically aligned facet is needed. A symmetrical diamond can have a uniform brightness reflection of light.
After the cutting process, it is necessary to polish every facet of diamond. With professional polishing techniques, a diamond will appear to be smoother and its value will hence increase.
Diamond Cut Grading
According to GIA, cutting is categorized into 5 different grades, which are Excellent (EX), Very Good (VG), Good (GD), Fair (F), and Poor (P).
EX is the highest grade which indicates perfect proportions and polish grade of round diamonds.
VG (Very Good)
VG cut grade indicates right proportions and polish, which in turn give outstanding brilliance and scintillation of round diamonds.
Good cut grade represents round diamonds which give substantial luster and brilliance.
F (Fair) and P (P)
Fair and Poor-graded diamonds have low grades in cut and polish, which are mainly caused by the limitation of the shape and size of the rough material.