Diamond Cut is the most important aspect in determining a diamond's beauty and is the most difficult for the consumer to judge when shopping for a diamond. It is the only factor controlled by man and for many years it has been the least understood by the consumer. The cut of a diamond is the arrangement of its facets, as well as the finish and proportions of a diamond.
With the recent introduction of the Cut grade by both the GIA (Gemological Institute of America) and the AGS (American Gemological Laboratories) labs the least understood and most important of the Diamond 4C's has been standardized. Both the GIA and the AGS labs have different approaches to grading the cut of a diamond, but both are scientifically-based proven systems. The GIA bases its Diamond cut grade on proportions and the AGS bases its Diamond cut grade on light performance. GIA uses a scale with 5 levels (excellent to poor) where the AGS system has 11 levels (0 to 10). The Diamond Cut grade is the biggest change in the diamond industry in the last 25 year.
A highly trained diamond cutter must first analyze a rough diamond before considering what diamond cut will complement the natural beauty of the stone. Interestingly, a diamond can only be cut by another diamond.
It is possible to have two diamonds that are equal in carat size, share the same color and clarity but look completely different. It all depends on the cut. Based on the cut, the weight of the diamond can be distributed differently to various parts of the diamond such as the crown and girdle. Also, the way facets are arranged and how brilliant the diamond appears will be determined by the way the diamond is cut.
Certified diamonds are anywhere from 20% to 60% more than non-certified stones. Stones under .18ct are normally not certified by GIA or AGS. 90% the diamonds you see in jewelry stores and online are non certified stones. Unless they say they are GIA or AGS and have documentation to back it up.
In 2005, the GIA introduced its 'Diamond Cut Grading System' for round brilliant diamonds. This system has been in development for fifteen years and the researchers at GIA have been perfecting a computer modeling system for round brilliants. They experimented on more than 70,000 stones in order to successfully establish this new grading system. The result of the research is that the system can now predict the cut grade for millions of various sets of round brilliant diamonds. This new 'Diamond Cut Grading System' analyzes the diamond's face-up appearance by using many different computer modeling techniques in addition to algorithms, which are used to evaluate the levels of brightness, fire and scintillation.
GIA is not an appraisal; it is a birth certificate to the diamond that gives you the information of the inclusions, cut, polish, symmetry ECT... of the diamond. No two diamonds are alike.
The science supporting the AGS Lab's cut grade system is the result of years of research, testing, and retesting by a team of gemologists, optical physicists, and mathematicians. In the AGS cut grade system, all facets of a diamond are measured in three dimensions rather than two dimensions. The AGS Lab uses a state-of-the-art ray tracing software to trace light traveling through a diamond. The software demonstrates the quantity and quality of the light being returned to the viewer. AGS Laboratories will now consider brightness, dispersion, leakage, contrast, and weight ratio, in addition to proportion, symmetry, and polish, when assigning a final cut grade.
Since GIA and AGS Labs use different scales and methods, this represents DiamondWaves opinion as to the equivalence of the two grading systems.
The following is a summary of individual metrics used by each lab for cut grading.
The GIA Cut scale levels are: Excellent, Very Good, Good, Fair and Poor. The GIA Cut grade assesses the diamonds in these primary ways:
Face-Up Appearance is the most important part of the GIA's cut grade assessment.
The AGS Cut scale levels runs from 0 for 'Ideal Cut' to 10 for 'Poor'. Because the AGS bases their cut grade on light performance this allows them to grade for shapes other than round. The AGS Cut grade assesses the diamonds in these primary ways:
Purchasing a diamond is one of the most exciting and expensive investments you will make so it is best to educate yourself about the physical properties of a diamond, particularly the anatomy, As your knowledge about the physical attributes of a diamond grows, so does your ability to purchase the best possible diamond as well as stay within your budget.
The optical characteristics of a diamond determining light performance and appearance.
The arrangement of a diamond's facets (a key part of how a diamond is cut) determines the sparkle and brilliance of the stone. Facets of a diamond can be flat, angular, or surface plains. A diamond that is poorly-cut will lack sparkle and a diamond that is well-cut can compensate for a small size or imperfect color or clarity.
The depth and width of the stone can affect the way light travels within the diamond and how it leaves the diamond, which directly impacts a diamond's brilliance. For example, if the diamond is too shallow, then light is lost through the bottom of the stone and causes a loss of brilliance. If it is too deep, then light escapes from the sides and creates a dark and dull appearance.
The goal in extracting the most beauty from the diamond is to have the light enter the stone and disperse as it bounces inside the stone through the different facets and produces sparkle and flashes of brilliant color. While doing this, the diamond should return as much light to the eye as possible.
A polished diamond's beauty lies in its complex relationship with light: how light strikes the surface, how much enters the diamond, and how, and in what form light returns to your eye. The result is a display of three attributes. Brightness is the combination of all white light reflecting from the surface and interior of a diamond. Fire is the colored flashes that can be seen in a diamond. Scintillation describes the sparkle of light you see in a diamond, and the overall pattern of bright and dark areas when you look at a diamond face-up.
A diamond is attractive when it is bright and fiery; when it has a pleasing, even pattern to its areas of light and dark (scintillation); and when it demonstrates a high level of craftsmanship. A diamond is less attractive if it is dark; if it is not fiery; if it has a distracting or unpleasant pattern; if it is carelessly polished; or if it is sloppily cut. Also, a diamond with a too-thin girdle may be attractive, but it is more susceptible to damage. A diamond with a thicker girdle or a larger total depth also can be attractive, but then the customer pays for unnecessary weight.
The cut of the diamond is determined by the anatomy of the diamond. The composition of the diamond is made up of diameter, table, crown, girdle, pavilion, culet, and depth.
Another process by which cut has a direct effect on how much light enters the diamond, and how brilliant the diamond will become, is a process called refraction. The brilliance of diamonds results from their high refractive index, a measure of how strongly a transparent material bends light rays. The key to a diamond's brilliance is that diamonds tend to bend light more so than any other natural substance.
Polish affects how light is able to pass through a diamond and is very important to a diamond's brilliance. You should only select a diamond that is laboratory certified with good, very good or excellent polish.
Symmetry is an important element of a diamond's finish. Symmetry refers to the size, alignment, and matching of the individual facets. You should only select a diamond that is laboratory certified with good, very good or excellent symmetry.