Diamonds are the most valuable gems in the world.  Because the quality of diamonds can vary so much, it is essential to have a universal grading system.  Throughout the 1940s and 1950s, the GIA (Gemological Institute of America) developed the standards for the 4 Cs.  This is so diamond laboratories have a defined protocol by which they can objectively compare and evaluate diamonds.  Although the GIA standards can be used for most diamonds, they are still developing a standard by which to measure the cut of shapes other than the round brilliant.  Cut is the most difficult to judge, because there are no standard ‘perfect’ proportions set for most shapes.

 

Carat

All diamonds and gemstones are weighed in metric carats.  Each carat is divided into 100 points; therefore, a 25 point diamond weighs 0.25 carats.  One full carat equals 0.2 grams.  While carat weight is definitely a consideration in purchasing a diamond, it cannot be the only factor involved.  Two diamonds of equal carat weight can be worth very different amounts based on the quality of the other of the 4 Cs of diamonds. 

 

Color

The color quality of a diamond is about not seeing color.  The value of a diamond increases as it nears colorlessness.  Of course, there is an exception to this, with the rare occurrences of diamonds in fancy colors from some mines.  Those are judged by the other 3 Cs.  But the diamonds most often purchased are ones that are as close to having no color at all as is possible.  GIA’s color-grading scale is the industry standard.  The scale is D-Z, with D being colorless and Z being near-colorless.  Within each letter grade, the GIA has a clearly defined range of color appearance.  Diamond color is judged by comparing them to other diamonds of already-defined color under specific lighting and precise conditions.  A very slight difference in color can make a tremendous difference in the value of a diamond.

 

Clarity

Diamond clarity is judged based on the lack of inclusions (internal flaws) and blemishes (external flaws) for each diamond.  Diamonds that do not have any of these ‘birthmarks’ are extremely rare, so a flawless diamond carries a much higher value.  According to the GIA International Diamond Grading System™, diamonds are grading on a clarity scale ranging from ‘flawless’ (FL) to ‘showing obvious inclusions’ (I3).  Truly flawless diamonds, even under 10X magnification, are extremely rare. 

The GIA Clarity Scale contains 11 grades.  Most diamonds fall into 2 categories: VS (very slightly included) and SI (slightly included).  To determine the clarity grade, the GIA system looks for flaws under 10X magnification.  The list of Clarity Grades is as follows:

Flawless (FL): No inclusions or blemishes are visible to a gemologist under 10X magnification.

Internally Flawless (IF): No inclusions but a few blemishes are visible to a gemologist

under 10X magnification.

Very, Very Slightly Included (VVS1 and VVS2): Inclusions are difficult for a gemologist to

see under 10X magnification.

Very Slightly Included (VS1 and VS2): Minor inclusions are clearly visible under 10X magnification to a gemologist.

Slightly Included (SI1 and SI2): Inclusions are visible to a gemologist under 10X

magnification.

Included (I1, I2, and I3): Inclusions are obvious under 10X magnification and may affect

the transparency and brilliance of the cut diamond.

 

Cut

The cut of a diamond refers to the proportions once it is shaped.  Even a flawless diamond can lose its beauty if it is poorly cut, and a more flawed diamond can be made to look beautiful if it is well cut.  Each diamond shape uses very specific formulas to cut the angles on a diamond.  Regardless of shape, each diamond gets its scintillation and brilliance during the cutting and polishing process.  During the process, the cutter shapes the facets to maximize the amount of light that enters the diamond to reflect back out through the top of the diamond.  A poorly-cut diamond (for example, one that is cut too shallow or too deep) will allow the light to enter the diamond and then escape through the bottom of the gem.  With little or no light reflecting back, the beauty—and value—of the diamond is essentially lost. 

 

The GIA grades cut only for round brilliant diamonds within the D-Z color range.  The precision of the cut of a diamond is what makes a brilliant diamond so stunning.  Traditionally, a round brilliant has 58 facets, with each one precisely cut to create three specific qualities: brilliance (total light reflected from the diamond), fire (the dispersion of light into colors of the spectrum), and scintillation (the sparkle created when the diamond is moved in light).  As of 2005, the GIA created a ‘diamond cut grading system’ for round brilliants falling into the D-Z color range.  Each GIA-examined diamond is given a grade from Excellent to Poor.

The Four C's of Diamonds

  keywords: Diamond Grading, Four C s, Diamond, 10x magnification


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