GIA & GemEx: What Is The Difference? | Zcova
GIA and GemEx Difference

GIA & GemEx: What is the Difference?

Choosing a diamond, especially the round brilliant diamonds raises a lot of questions – more than you’ve ever imagined. Round diamonds are traditionally the first and most popular diamond for engagement rings. They have a classic uniform and symmetrical shape that consists of 57 facets, which qualifies them a brilliant cut. So what do you need to know if you’re planning to buy a round brilliant diamond? 

The technical information alone can be daunting at first. But don’t worry! In this blog post, our in-house GIA graduate gemologist will share with you some in-depth knowledge of diamond certificates to be a smart buyer. 

A diamond certificate, which is also called a diamond grading report can definitely help you as it contains most of the important information you should know. At ZCOVA, we are the only online diamond company in Malaysia & Singapore to provide dual certificates of GIA & GemEx. 

Now, you may be wondering, “What exactly are GIA and GemEx and why are they so important for my round brilliant diamond?”   

Gemological Institute of America (GIA)

GIA is internationally recognised as the leader in gem education, research and laboratory services. Today, GIA grading certificates are considered the hallmark of integrity in the diamond world. 

The GIA diamond grading report provides scientifically determined information on shape, clarity, colour, cut, carat weight, proportions, finish, and treatments. It also includes a diagram of the diamond showing any inclusions that affect clarity.

GIA Cert

Sample natural diamond reports from GIA.

GIA also laser-inscribed an identification number on the diamond’s girdle that is visible under 10X magnification (See actual diamonds in 360-degree). The numbers will match the one on your certificate and it serves as an identification that it is your chosen diamond. 

Diamond Inscription and GIA Cert

This is how GIA diamond inscription is viewed under a microscope, giving you peace of mind.

4Cs of Diamonds


A diamond is graded to determine its relative absence of colour, based on the GIA Colour Scale which ranges from D (colourless) to Z (light yellow or brown). GIA assigns a colour grade by comparing each diamond to a master set in a highly controlled lighting and viewing environment.


A diamond is assigned a clarity grade based on the number and placement of internal features (inclusions) and surface characteristics (blemishes) that are visible under 10x magnification. The GIA Clarity Scale contains eleven clarity grades ranging from Flawless to I. 


Refers to how the proportions and finish of a diamond affect its overall appearance and quality. Cut is graded on a scale from Excellent to Poor and incorporates the diamond’s brightness, fire, scintillation, weight ratio, durability, polish and symmetry. GIA only provides a cut quality grade for standard round brilliant diamonds.

Carat Weight

GIA measures carat weight, the standard unit of weight for diamonds and other gemstones, using a highly precise electronic scale rounded to the nearest hundredth of a carat. 


GemEx comparison between median and Lumos by ZCOVA

GemEx is an independent laboratory that focuses on light performance or the movement of light through the diamond.

GemEx measures a diamond’s white light (brilliance), colour light (fire), and scintillation (sparkle). The GemEx Light Performance Report illustrates the measurements for your diamond in a three-bar graph. 

GemEx five light measurements

The report also shows images of your diamond under five different lighting views.

Superior performance in any of the three light categories yields a beautiful diamond. In short, GemEx says a diamond’s beauty is determined by the way it reflects and refracts light.

RELATED: How to Read a GemEx Report

What Happens When You Have Both GIA & GemEx Certs?

ZCOVA Dual Certificate

Dual Certificates help you to make an informed diamond purchase as they are unbiased opinions of diamond quality.

Well, you’ll have the best of both worlds! As most customers are new to diamond grading, customers can use the help of diamond certifications to level the playing field. Understanding the light performance of a diamond provides a complementary set of data that you can compare side by side with a standard GIA report. 

Small differences in diamond grading can make hundreds or thousands of dollars difference. Hence, the credibility of a diamond’s certification is huge. Buying a diamond with certificates should give you peace of mind, knowing your diamond is equivalent to the quality and value that is claimed. 

RELATED: 5 Tips On How To Save For An Engagement Ring


LUMOS by ZCOVA Diamonds

Understanding that customers have asked for the diamond with the best cut and brilliance, but not knowing how to pick one, we found a solution to this – LUMOS by ZCOVA diamonds. With this, customers can be confident that they’re getting the best diamond with the most value.

GemEx comparison between good and excellent diamond

Each LUMOS by ZCOVA diamond is #CertifiedBrilliant, carefully selected by our in-house GIA graduate gemologist and to ensure they meet our strict requirements. This quality assurance comes at no extra charge.

If you have questions about lab certifications or need assistance to ensure you’re getting high-quality diamonds, please don’t hesitate to reach out to our in-house GIA graduate gemologist for a virtual appointment. We’d be more than happy to answer your questions. 

Read more of what you’ll be getting from ZCOVA Dual Certificate: