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Diamond Grading and Certification

Before you buy loose diamonds, you need to make sure that you understand how your diamond or diamonds have been assessed and what its grading or certification really means. (Note: Grading and certification applies to loose diamonds only, not a finished piece of diamond jewelry.)

Diamond Grading Certificates

The Difference Between Certificates and Appraisals
If you are wondering how much to pay for your loose diamonds, then you need to compare, wherever possible, like for like. You can only do that in the world of diamond sales by knowing about diamond quality and that is where grading certificates can help. Diamond grading certificates do not assign a monetary value to a diamond or diamonds. An appraisal, on the other hand, will include a price, but this can be set by anyone (including the vendor) and is subjective to both mark-up, the diamond markets and diamond merchants.

What A Diamond Grading Certificate Includes
Diamond grading certificates or reports are often likened to a 'fingerprint' for each diamond as they provide technical detail about the stone to verify its value and its identity. It includes information about:

  • A diamond's exact measurements and weight
  • Details of the diamond's quality and cut
  • The individual characteristics of the stone.

The part of the certificate with probably the most importance for you is the Light Behavior or Cut information as it includes light behavior grades and numerical measures for brilliance, sparkle and intensity. In other words, it tells you how beautiful the stone is.

Credentials of Diamond Certificate Issuers
Diamond laboratories throughout the world issue diamond grading certificates, so you should look for diamonds with certificates issued by the most widely recognized and regarded grading labs. Not all certificates are of equal, if your diamonds are non-GIA or non-AGS certified for example, you should ask for and check out the credentials of the grading lab.

Issuers of Diamond Certificates and Reports

  • Gemological Institute of America (GIA) - A non-profit institute that created the 4 Cs (Cut, Clarity, Color and Carat). Issues reports (rather than certificates) and do not include aspects such as crown height percentage, pavilion depth percentage, crown angle and pavilion angle). However, this is one of the most highly regarded and recognized grading labs in the world.
  • American Gem Society (AGS) - Has a cut grade numbered from 0 to 4, 0 being the most desirable down to 4 being the least desirable.
  • Hoge Raad voor Diamant (HRD) - The European counterpart to the Gemological Institute of America. Recognized by the EU (European Union), its grading certificates are legal documents in the Far East and in Europe.
  • International Gemological Institute (IGI) - This institute focuses mostly on appraisals of diamond engagement rings.

Diamond Certificate Authenticity
Remember, your grading certificate is only as good as the laboratory that issued it, so it's worth checking that all of the following details are included: Authorship - Check out the grading lab's credentials.

Date - A current date issued at the time of inspection will help ensure that the diamond has not been altered (e.g set in a ring or piece of jewelry and/or previously worn).

Cut - Check this evaluation has been done on the actual diamond, not a model. - Find out more about Diamond Cut.

Carat - This refers to the weight of the diamond and not the actual size of the diamond. - Find out more about Diamond Carat.

Measurements - Evaluate the measurements. For round diamonds, the proportions are important whilst for fancy-cut diamonds the length-to-width ratio is of more importance. - Find out more about Measurements.

Clarity - It's important to note that clarity gradings vary between grading labs but if you shop 'like for like' using reports issued by the same laboratories, you should end up with the diamonds you want. - Find out more about Diamond Clarity.

Color - Again, grading systems can vary but generally colorless diamonds are the most expensive and desirable. (Rare diamonds of intense and vivid coloring are highly prized and therefore extremely expensive.) - Find out more about Diamond Color.

Proportions - Check the depth of the diamond - the desired depth percentage depends on the shape of the diamonds. This should also include information about the table width, girdle and culet.

Finish - Look for 'good' or better gradings for polish and symmetry.

Diamond Facts

Find out more about:  Diamond Grading    |    Diamond Carat    |    Diamond Color    |    Diamond Clarity    |    Diamond Cut

"Diamond grading certificates and reports - what they are, who issues them and what information they should include for diamond buyers."

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