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Diamond Certification

Updated: Sep 18, 2023

Lonite GIA Diamond Certificate
Lonite GIA Diamond Certificate


Diamond Certification

Buying a diamond is one of the most important purchases in one’s life. As such, this decision goes above and beyond simply selecting whichever stone looks pretty, to closely examining the quality and characteristics of the diamond in question, based on its diamond certification.

What is a Diamond Certificate?

A diamond certificate, also known as a diamond report, is a document that describes the unique features and qualities that affect the value of a specific diamond, for example color, clarity, cut, carat weight, the origin of the diamond and any additional processes previously carried out to modify or alter the appearance of a diamond. Contrary to popular belief, diamond certificates do not guarantee or certify that a stone is of high quality. They simply describe the diamond’s characteristics based on an evaluation done by experts in gemology.

As part of the diamond certification process, some diamond grading labs engrave the girdle of the gemstone with a serial number that matches the one on the diamond’s certificate. This is especially useful in recovering the diamond if it’s ever lost or stolen.

Contents of a Diamond Certificate

Diamond certificates differ based on the diamond certification lab. However, most certificates contain the following information:

  • The Unique report number

  • Date of examination

  • Exact measurements of the diamond

  • Cut style and diamond shape

  • Clarity grade

  • Color grade

  • Carat weight

  • Clarity grade

  • Proportion diagram

  • Diamond plot that shows a diamond’s inclusions and blemishes

  • Polish grade

  • Girdle thickness

  • Security features

  • Relevant notes

  • Explanation of grading

A Diamond Plot Showing Both Visible and Microscopic Inclusions in a Diamond
A Diamond Plot Showing Both Visible and Microscopic Inclusions in a Diamond

It is important to note that diamond grading is subject to personal interpretation. This explains why different diamond certification labs can award different grades to the same gemstone. Before committing to a diamond certification lab, research their reputation and the consistency of their diamond grades. A diamond certification lab that continuously offers high diamond grading for low-quality diamonds doesn’t give value for money since a slight difference of one color or clarity grade can translate to as much as 25% increase or decrease in the price of a diamond.

Types of Diamond Certificates

There are a number of diamond grading laboratories around the world, all of which produce their own diamond certificates based on their own terminology and standards. Some of them include:

A GIA Diamond Grading Report
A GIA Diamond Grading Report

The Gemological Institute of America (GIA) is a nonprofit institute dedicated to research and education in the field of gemology. They are potentially the best known and most respected diamond certification lab because of their consistency in diamond grading.

GIA developed the International Diamond Grading System based on the 4Cs as a standard to compare and evaluate the quality of diamonds. They also provide training for gemologists and jewelers across the globe in order to ensure that their strict standards are met everywhere.

AGS (American Gem Society) prides itself on being the first lab to provide diamond cut grades, and just like the GIA, this diamond certification lab is popular for the consistency they have exhibited in diamond grading over the years. According to industry experts, AGS is also believed to have the easiest diamond grading reports among all the diamond certification labs in the UK and USA.

Till date, the grading system at AGS is unique and in fact, their cut grade is the only one of its kind in the industry, since it uses number scales from 0 to 10. However, it is worth noting that AGS standards on color and clarity grading are somewhat looser than those of GIA.

The International Gemological Institute (IGI) started off as the most popular diamond certification lab for major jewelry chain stores, especially those based in the USA. Their approach is designed to impress retailers, which means they’re fast and efficient, but often lax in their grading.


EGL stands for European Gemological Laboratories. It’s a collection of diamond certification labs, independently owned in Europe and the UK and they tend to have a looser approach to diamond grading, you’ll often find the grade is one, or even two, levels higher than the USA-based GIA and AGS.

EGL diamond certificates are generally discouraged due to the over grading and quality misrepresentations at the EGL diamond certification lab.


Hoge Raad voor Diamant (HRD) is a European based diamond certification lab.

Again, this is a diamond certification laboratory built for diamond sellers as they consistently over-rate diamonds, in order to increase potential profits for diamond retailers. Experts estimate that the color and clarity are often two grades higher than GIA diamond grading and the prices are also relatively higher than GIA diamonds of the same grade.


Gemological Science International (GSI) is a newcomer on the diamond grading scene. The approach of this diamond certification lab is strictly business.

Instead of focusing on the quality of the diamond and issuing the appropriate diamond certificate, GSI has committed to providing cheap assessments to the biggest jewelry companies in the USA and beyond.

Unfortunately, this is not a diamond certificate you should be inspired by. Research suggests that their diamond grading is consistently looser than GIA, AGS, IGI and HRD diamond certificates altogether

The Diamond Certificate Is Used as Proof of the Diamond’s Value and Quality
The Diamond Certificate Is Used as Proof of the Diamond’s Value and Quality

The detail on the diamond certificate gives you all the information you need to know about your diamond and it also allows you to compare it with others so you can make a logical and well informed purchase decision.

The larger the purchase the more essential it is to have a diamond certificate from a USA or UK based lab that you can trust, such as GIA. It’s up to the customer to make sure the grading of the diamond matches the jeweler’s description of the gemstone.

It’s worth noting that a diamond certificate from one of the lax labs is still better than no certificate. Buying a diamond is usually a significant financial and emotional commitment. The diamond certificate ensures you’re getting what you’re paying for.

Diamond Certification vs. Diamond Appraisal

It should be noted that a diamond certificate is not the same as a diamond appraisal. The diamond certificate confirms that the diamond has been examined by a gemological lab and its various qualities and features have been assessed and listed.

In contrast, a diamond appraisal simply indicates how much a diamond is worth in monetary value based on current market conditions and the quality of the diamond.

The diamond certificate is an essential part of your diamond purchase. However, make sure to also get a diamond appraisal before making any purchase as this will help to ensure you’re getting the quality of diamond that you’re paying for.

Unless you’re a highly skilled jeweler or gemologist, it’s impossible to determine whether a diamond is worth its price tag by simply looking at it. That’s why you need both a diamond appraisal and a diamond certification from a reputable and independent diamond certification lab in order to ensure that you get value for your money.

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