Remember that diamond certificates are not guarantees, valuations or appraisals. While professional labs employ experienced well-trained graders and use the most accurate gemological instruments to grade gemstones, laboratories make no warranties regarding the accuracy of their certificates. Diamond grading, like diamond cutting, is both an art and a science.Take the time to understand how to read a certificate, however, your diamond purchase should not be based solely on this document. It cannot replace a visual inspection of the diamond you are considering. Some diamonds are beautiful even if they don’t look good on paper.
Issuer of the Report
The Four C’s
Unique ID Number
The certificate will have its own identification number.
Look for a statement attesting the origin, i.e., whether it is a natural diamond or it has been enhanced. Labs do not grade fracture-filled diamonds.
Shape, such as round, pear or oval, and cutting style, such as brilliant or step cut, are noted on a certificate.
Shape and Cut
When diamonds first began to be given as engagement rings, settings were elaborate and did not necessarily showcase the diamond in its best light. It actually wasn’t until the discovery of diamond mines on the African continent in 1870 that diamonds became accessible to a wider public, increasing demand and influencing design. Subsequently, diamond jewelry began to be designed to demonstrate the unique beauty and brilliance of diamonds.
Major laboratories measure diamonds in millimeters, typically to the hundredth of a millimeter. Exact dimensions are very important in identifying a diamond, as it is unlikely that two diamonds will have identical weight and dimensions.
Good proportion–particularly the depth and table percentages–influences the brilliance and fire of a diamond. In fact, proportion is as important as color and clarity grades.
Clarity and Color Grades
Most diamond buyers know their 4Cs: cut, color, clarity, and carat weight.
Some diamonds will appear to exhibit different colors in ultraviolet light. This property is called fluorescence.
What is a “clarity enhanced” diamond?
Some diamonds with surface reaching fractures are filled with a glass-like compound to make them look better. Like cosmetics, this process merely improves the appearance of the diamond compared to what it would look like without the treatment; it doesn’t improve the clarity of the diamond. It’s a legitimate process but jewelers are required by law to disclose whether a particular diamond has been treated. Most major gemological laboratories do not certify clarity-enhanced or fracture-filled diamonds because the process is not proven to be 100% stable and may change during jewelry repair procedures.
What is SI-3?
Diamonds graded as SI-3 (‘slightly included”) contain clarity characteristics that are very easy to see under 10X magnification. The SI-3 category lies between the SI-2 and the I-1 grade.
SI-3 was introduced to the diamond trade in 1992 to better serve the changing needs of the marketplace. The following year the Rapaport Diamond Report created an SI-3 price column, and the grade has gained wider acceptance over the past decade.
While not all labs have adopted SI-3, EGL USA began using it on its diamond grading reports in 1997. This step was validated by important global industry organizations that officially recognize the grade, among them the World Federation of Diamond Bourses and the International Diamond Manufacturers.