There are many guides to how diamond cut effects its beauty available on the internet, and we encourage you to read a few before making your decision! However, the information in other guides may not be presented in a way that is easy for you to understand or may be overly technical. Our guide will attempt to give you an understanding of what effects each element of diamond cut has on the beauty of a diamond.
This is the most comprehensive diamond cut angle guide you’ll find on the internet. It’s been painstakingly researched to provide the most accurate information on diamond cuts, angles, and shapes.
The guide has been divided into the following sections:
1. What Is The Proper Diamond Cut?
2. Which Cut Do I Choose?
3. Terminology: A Visual Guide To Understanding Diamond Cuts And GIA’s Grading Scale
4. The History Of The 4C’s
5. How Cut Affects Brilliance, Fire, Scintillation, Colour And Contrast
6. GIA Diamond Grading Report: Tips for Reading A Report
7. Diamond Cut Ratios For Rounds And Emerald Cuts
8. Diamond Cut Calculators & Tools For You To Use
9. Famous Diamond Cuts: Information About Famous Antique & Current Cut Styles
Diamond cut is a factor in diamond beauty and brilliance. It is not a major factor. The most important factors are the 4 Cs, cut, color, clarity and carat weight. But knowing about diamond cut can help you understand what makes a diamond beautiful.
The inclusions within a diamond can be cut to enhance the beauty of the diamond. The term used for this is a “beauty enhancement”.
The angles of a diamond and how they are cut will affect how light is reflected from the surface of the diamond. This is called brilliance. The concept of brilliance was established by Marcel Tolkowsky in 1919 and later modified by others. Tolkowsky’s original formula is known as the Tolkowsky formula.
Tolkowsky Formula: [B = (C-ID)/2] + .02A + .15A2 + .05A3
Where B = brilliance, C = crown angle (lateral view), I = groove angle (lateral view), A = table percentage, and D = pavilion angle (oblique view).
In plain English, this formula states that the amount of brilliance of a diamond is determined by its overall proportions and shape, specifically:
1. The higher the crown angle, or upper half of a diamond, the more light that can bounce off its table and out through the top.
2. The more shallow the depth of a cut, or lower half of a diamond, the more light that can bounce off its pavilion, or back side, and out
The practice of giving diamond cuts names began in the 1930s, when Marcel Tolkowsky, a Polish immigrant to England, published a book called Diamond Design. As with many things in diamond cutting, there is no universally accepted standard for what each cut should be called. There is a system used by the Gemological Institute of America, and another used by the European Gemological Laboratory.
Determining what constitutes an ideal cut has been debated for over 100 years. The GIA considers 57 degrees to be optimal, while the EGL uses 60 degrees — among others.
It is well worth noting that neither organization has “established” an ideal angle as a standard—it is simply the angle they use to grade diamonds on their own scales. It’s also worth noting that when it comes time to cut the stone, nothing guarantees that it will end up with the angle at which it was graded because of the variables involved during the cutting process itself.
Tolkowsky’s original system had five categories: excellent, very good, good, fair and poor. The GIA scale removes two of those categories (which can lead to confusion). These days most jewelers use one or both of these scales when looking at diamond cuts and angles.
The most important diamond characteristics to know when considering a diamond ring purchase are the Cut and Clarity. The cut refers to the faceting of the stone, while clarity refers to the inclusions (or lack of) in the stone.
The four C’s is a grading system for diamonds based on the 4 most important characteristics of each and every one. The cut (or craftsmanship), color, clarity and carat weight. Each of the 4 C’s are equally important, but if you are ever told that one is more important than another, run for the hills!
Diamonds that are cut correctly reflect light in such a way as to cover maximum surface area with the least amount of weight. This results in maximizing brilliance, fire and scintillation – creating a diamond that glows.
The cut refers to the symmetry and polish of a diamond. A well cut diamond will have 57 or more facets (flat surfaces) on each side of the stone. These facets, when combined with the proper cut angles, create the brilliant look seen in high quality diamonds. The table below is an example of how a diamond’s quality is expressed by its proportions:
Proportions expressed as percentages
Avg Cut Ideal Cut Intrinsic Quality* Excellent 0.90 0.96 100 Very Good 0.84 0.91 95 Good 0.72-0.79 0.85-0.89 90 Fair 0.70-0.75 0.76-0.84 85 Poor >0.