The round brilliant shape diamond has been, and continues to be the most popular diamond shape. As such, this information will focus on determining what criteria constitutes a well cut round brilliant diamond. An internationally accepted system for visually evaluating the appearance of fancy-cut diamonds does not exist at this time.
Diamond Cut Is Arguably The Most Important Of The 4Cs.
Diamond Cut Vs Diamond Shape
The first point that we have to clarify is not to confuse the terms diamond 'cut' with diamond 'shape'. Diamond shape refers to the general face up outline of the diamond (examples: round, princess, emerald, radiant, etc.). The diamonds 'cut' refers to the face-up appearance, design and craftsmanship of a diamond; not the shape. Having said that, the terms are often interchangeable when dealing with people in the industry; for example, it's not unusual for someone to request a 'round brilliant cut' or a 'princess cut', it is simply a matter of determining the context of the conversation. “Make' is another common term used to refer to a diamonds cut quality.
Diamond Cut Grade
Selecting the grade of cut is really a matter of personal preference; but to help you make the best selection, you need to understand how the various cut grades are assigned.
Thanks to systems developed by independent diamond grading laboratories, the diamond industry and public can now use cut along with colour, clarity and carat weight to assist in making an informed decision when purchasing round brilliant diamonds.
Because diamond cut is perhaps the most important of the four Cs, it's important to understand how this quality affects the properties and values of a round diamond.
Diamond cut quality encompasses factors relating to three main components:
1. Face up Appearance - Brightness, Fire & Scintillation
2. Design - Weight Ratio & Durability
3. Craftsmanship - Polish & Symmetry
When looking at a round diamond cut grade, each component is assessed individually, taking into account the relative importance of that component in the overall cut quality of a round brilliant diamond, and the ability of an average, experienced observer to consistently see the differences in cut quality based on these components.
Face Up Appearance
The sum appearance of a polished diamond when it's viewed in the table up or face up position. This appearance includes what is seen when the diamond is "rocked" or "tilted."
Brightness, Fire and Scintillation are appearance based aspects.
Cut gives a diamond its 'brilliance', which is the brightness that seems to come from within a diamond. The angles and finish of any diamond are what influences its ability to handle light, which leads to brilliance as perceived by the person viewing the diamond.
'Fire' refers to the coloured light reflected from within a diamond. White light exiting a diamond is separated into the colours of the rainbow just like a prism. Also called 'refraction' or 'dispersion'.
'Scintillation' is the contrast between the light and dark that alternates from facet to facet and attracts our eyes as either the diamond or the person looking at the diamond moves.
Design refers to the decisions made during the cutting process that determine a diamond's physical shape.
Diamonds are sold by weight and not by visible size or measured diameter, so 'weight ratio' is a comparison of a round diamond's weight in relation to its diameter. Weight ratio is used when assessing a diamonds cut grade to look for any hidden or unnecessary weight. If a round brilliant has more than a specified tolerance of extra weight that does not contribute to a larger appearance or better light performance, then the diamond will receive a lower cut grade.
'Durability' is basically the risk of damage inherent in a diamonds proportions. For example, an extremely thin girdle could potentially chip and weaken a diamond.
Craftsmanship is a description of the care that went into the crafting of a polished diamond.
'Polish' is a measure of the surface finish and the degree of smoothness of each facet; while 'Symmetry' measures how well the facets align, match and intersect with other facets.
As mentioned at the start, this is a very simplistic breakdown of cut; and based on the assessment of these seven components, in a variety of combinations, a grading laboratory is then able to assign a cut grade.
GIA assigns one of the following five possible cut grades based on the above criteria:
Excellent, Very Good, Good, Fair, and Poor.
Because the cut grade is determined from a combination of measured parameters and visual observations such as table size, pavilion angle, crown angle, lower half length, star length, girdle thickness, culet size, symmetry, polish, etc.; to give an exact definition for each of the five cut grades would be very time consuming.
GIA Cut Grading System
For more detailed information, follow this link summarising the main concepts of the G.I.A. Cut Grading System for round brilliant diamonds.
Obviously, the cut grade can affect the value of a diamond, with higher cut grades demanding a premium, and lower grades receiving bigger discounts.
A diamonds cut is extremely difficult to analyse or quantify, and while it's important to consider the many individual components when assessing the overall cut appearance and quality of a round brilliant diamond, an individual's personal preferences also plays a significant role; after all, it's individuality and taste that determine fashions and transforms each stone into a unique work of art.
For additional information regarding what factors determine a diamonds cut grade, please don't hesitate to contact Australian Diamond Network for assistance.