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To determine a diamond's cut grade, an optical measuring device creates a three-dimensional model to determine the diamond's proportions and angles. The interrelations between these various dimensions will greatly affect how light reacts once it enters and how it behaves upon exiting the diamond. By using sophisticated computer modeling, it is possible to trace light behaviour and measure its levels of brilliance, fire and sparkle as it exits the top of the diamond, referred to as the face-up appearance by gemmologists.
The GIA only applies ideal/excellent cut grade parameters to round brilliant stones at this time. When a GIA cut grade is not available, Blue Nile provides one, allowing you to compare diamonds using consistent criteria.
While both cuts are of a very high quality, Astor by Blue Nile™ diamonds are cut to gather and reflect the most light possible. They are graded by both the Gemmological Institute of America - the world's most respected independent laboratory, and GemEx - the leader in light measurement, to guarantee their uncommon brilliance.
Polish describes the smoothness of a diamond's facets, and symmetry refers to the alignment of the facets. While polish and symmetry are worthy of noting, cut grade is far more important. Polish and symmetry can be helpful in choosing between two diamonds that are otherwise identical.
Fluorescence refers to those diamonds that produce a visible reaction when exposed to ultraviolet radiation. In laboratory experiments with both trained gemmologists and individuals with no diamond experience (meant to represent the Jewellery-buying public), no relationship was found between fluorescence and a diamond's overall appearance. Diamonds with a strong or very strong fluorescence are a better value for the end customer because the market prices them slightly lower than diamonds with faint or negligible fluorescence.
Coloured diamonds are an extremely rare, natural phenomenon of nature. If, while diamonds are being created deep inside the earth, they are exposed to certain trace elements, the result can be a coloured diamond in almost any hue of the rainbow. All Blue Nile coloured diamonds possess natural colour and are never exposed to artificial coloring techniques such as dyeing or irradiation. As with all Blue Nile loose diamonds, each coloured diamond is accompanied by a Gemmological Institute of America (GIA) report, which lists the diamond's specifications (e.g. colour grade) and natural origin.
Clarity is a measure of the number and size of the tiny imperfections that occur in almost all diamonds. Because these imperfections tend to be microscopic, they do not affect a diamond's beauty in any discernible way. Thus, while the brilliance and sparkle of a well-cut diamond can help camouflage the imperfections of a diamond with a lower clarity grade, it is difficult to imagine a scenario where a diamond's imperfections are so large and prominent as to mar a diamond's sparkle and brilliance. Regardless, Blue Nile would never sell a diamond of such low clarity.
For a three-stone ring, Blue Nile recommends that you choose the same cut grade for each of the diamonds, but colour and/or clarity can differ. For colour, there will not be a visible difference within three grades. For example, D, E, and F will each look the same. For clarity, anything VS2 or above will appear the same.
The International Gemmological Institute (IGI) and the European Gemmological Laboratory (EGL) are two other independent diamond grading laboratories. Blue Nile does not carry diamonds certified by these laboratories.
With the GemEx Certificate, you know how your diamond performs. Each and every diamond has been scientifically measured for its Light Performance certificate. The five diamond images on the front of the certificate are the actual images of the diamond that you own or are going to purchase. These images from the BrillianceScope are used to evaluate the percentage of white light and colour light that the diamond returns and the number of points of light that turn on and off as the diamond moves. GemEx ensures accurate brilliance, fire and sparkle results by measuring every diamond at multiple light angles. The bar graphs show how your diamond compares to all others in the world in each category (i.e. Round or Princess cuts). GemEx developed the scales for each shape by measuring tens of thousands of diamond to determine the range of brilliance, fire and sparkle possible. The IdentiView image reveals the craftsmanship and symmetry of the diamond. Learn more about the GemEx Diamond Light Performance Certificate here.