How to Read a GIA Diamond Grading Report

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HomeDiamond AdviceHow to Read a GIA Diamond Grading Report

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A major purchase like buying a diamond should not be rushed. It should actually be the result of self-education and then narrowing down the qualities in a diamond that are most important to you. Your principal concern is likely, "Is this a real diamond, and if so, what is the quality?" You'll want to know that your diamond is correctly identified as presented to you in the store. A GIA report is one way to understand exactly what you are buying.

Why We Need a Diamond Report

How do we accomplish the rather complex task of understanding a diamond's quality? A diamond grading is one important tool. Several labs across the United States and abroad are made available to consumers for this purpose. Importantly, a diamond is offered for sale without having a grading report does not mean that it is not a good stone, or is not even genuine. But having a grading report — especially for the consumer — provides a huge advantage and brings peace of mind. You can compare and contrast pricing for similar diamonds based on the report for your stone. It can also help when you go to 'trade up' for a larger stone in the future or even if you want to sell your diamond at a later date. And it's essential if you want to insure your diamond jewelry.

Start at the Top

GIA (Gemological Institute of America) is the foremost independent grading lab in the world. It examines diamonds and issues impartial evaluations for stones submitted to them. Both the trade (auction houses, retailers, and suppliers) and the public can submit diamonds for a fee and receive a grading report.

What is it? What is it Not?

First, a GIA diamond grading report is a document issued by GIA Labs. They carefully examine your diamond with the latest grading instruments and techniques to reach specific quality conclusions. It verifies the important characteristic of the stone. Is it natural diamond? Or is it another stone altogether? Next, the stone goes through their systematic procedures and records various characteristics of that stone. Every stage of examination helps support and deliver a final quality grade that appears on the report.

What a GIA diamond grading report does not produce a valuation of the stone fixed to those results. It is not an appraisal. The reason is pretty straightforward. The purpose of the diamond grading report is to establish its quality, irrespective of whether the owner is a member of the trade or a consumer.  When the stone gets into the hands of the retailer, he or she will establish their markup appropriate for their market. If the report is for a consumer who owns the diamond, they will have a document that verifies the quality components of their diamond. Then they can search both online sellers and retail settings to understand how the market values their stone at any time. Keep in mind, the dollar value of diamonds fluctuates over time due to the economy, and supply and demand.  

Just the Facts Please

A GIA diamond grading report assigns a unique number to the stone when it first enters the facility. Therefore, the lab professionals are unaware who the stone belongs to thus assuring everyone of an impartial examination and grading report.

Because a GIA diamond grading report is quite detailed, and uses the lexicon of the trade, it can be baffling to the consumer. Let's look at various parts of a GIA diamond grading report, and understand what it means so you'll actually be comfortable when reviewing your own diamond report.

Dissecting a GIA Natural Diamond Grading Report

Let's examine Blue Nile's facsimile of a GIA grading report for a 1.01 carat princess cut shown here:

Square princess cut diamond at Blue Nile
GIA report for this diamond at Blue Nile

Prominently displayed on the top center of the GIA report is the report's unique identification number, assigned to it when it was accepted at the lab. In the upper left-hand vertical column, we see the date of the exam, the report number, the style of the cut, and then—here's where it starts to vary considerably—the measurements. For each cut—be it round brilliant, emerald cut, pear shape or more, there are parameters considered ideal for the cut, which reflects the industry's consensus of its ideal form. Trade members closely scrutinize and review those measurements to assess how a stone measures up to its ideal standards and proportions (more on proportions below!).

Grading Results

Just below the general information about the report are the grading results. These identify the stone's carat weight, color, and clarity. These characteristics are familiar to you if you understand the 4 C's of a diamond (carat, color, clarity, and cut). Let's explore these in detail:

Color: One key way to differentiate the quality of diamonds is to look at their color. The color grading scale is located on the right side of the report, from D (colorless) to Z (light color). Your color preference depends on the type of diamond you are looking for. Colorless diamonds tend to command the highest prices, but more recent trends have seen an uptick in demand for diamonds with some color.

Clarity: Another key way to distinguish one diamond from another is based on clarity. The clarity scale is located on the right side of the report. It ranges from Flawless to Included. Flawless diamonds command the highest prices, with included diamonds seeing the lower range of prices. However, many inclusions are very hard if not impossible to see with the naked eye, so you may be ok with your diamond having a few inclusions that you cannot see!

Cut: Finally, the cut of a diamond is critical to its appearance. The cut dictates the fire and brilliance of a stone. There are many different types of cuts, so it is important to figure out which one suits you best.

There may be thousands of 1-carat emerald cut diamonds seen at the laboratory in a years' time. But beyond its carat weight and shape, color, clarity and cut distinguish these stones from one another.

Additional Grading Information

Farther down the right side of the report under ADDITIONAL GRADING INFORMATION, you'll see 4 more recorded observations. These are more nuanced, and as a consumer, you'll not be able to fully appreciate how they arrived at the grading conclusions for each, but it does help to see your stone's grade -as a means to compare and contrast it to other diamonds.

Polish—describes the extent to which the diamond polisher expertly (or not) completed his cut and polish process on the stone. These details are observed under magnification by a knowledgeable professional. But the outcome can be one of an extraordinarily dazzling stone—when done excellently, or a dull, lifeless stone when little care was given to its finish. 

Symmetry—describes the overall balance and perfection of the shape. If it's a round brilliant, is it completely round, with no lopsided (out of round) portions? Does the emerald cut have equal sides and straight lines as expected? The slightest off-perfect shape bears considerably upon its grade. An untrained eye may miss this altogether—which is exactly why a trained professional in a GIA lab is essential to grading these minute details.

Fluorescence—the diamond is put in a controlled environment to observe any emission of fluorescence under UV (ultraviolet) lighting. This is another way to absolutely identify your diamond as not many diamonds have this trait. There is much debate on the pros and cons of diamond fluorescence. Some feel a "little fluorescence" aids in making a lower color grade stone appear whiter. But too much fluorescence, it is thought, can make the stone (in normal lighting) look a bit 'sleepy' or hazy. These are subjective opinions, and every diamond owner exerts their own judgement as to the beauty of their individual diamond.


The proportions of a stone also affect its value. The measurements listed above affect the proportions of the stone, which are found in the illustration at the center of the report. There is a helpful side view diagram of the diamond to depict its relative depth percentages of the entire stone. Each diamond shape has its ideal proportions, and this diagram helps consumer and retailer understand how this diamond stacks up to its ideal proportions. Ask your retailer what the ideal proportions of your stone shape should be, then compare those percentages to your stone. Most stones vary slightly from the 'ideal' of course.

Here you can get a quick overview of what makes a modern ideal cut the model of perfection:

Diamond cut diagram from James Allen

Clarity Characteristics

Below the proportions image is a fascinating plot shows you what kinds (internal, external etc.) of inclusions (flaws) your stone has, including their location on the stone. Light colored inclusions do not often affect the beauty of a stone. Likewise, the place on the stone where the inclusions are located can also impact -or not so much—the beauty of the stone.

Inclusions closer to the edge of a stone may become obscured by its setting, or at least hidden by numerous facets that are closer to the edge. No other stone will have these exact inclusions—and in the exact places as appears in your diamond, this clarity plot becomes another way to positively identify your stone.

Learn more about how clarity impacts your diamond:

Clarity scale from Blue Nile

The grading report may seem mysterious at first—but by looking at each section item by item, you'll soon have a clearer grasp of how quality characteristics are systematically recorded for a diamond. You'll also be able to compare your diamond's report to others to determine the best stone for you.

Everyone has different criterion when selecting their diamond. While some people want the largest -showiest stone for their money, others will insist on the highest color or clarity that money can buy. There's no right or wrong when it comes to diamond selection. It all boils down to what's right for you. By understanding how to interpret the GIA diamond report, you'll be able to hone in on the perfect diamond for you.

Diana Jarrett GG RMV

Creative writer, author and Gemologist, Diana Jarrett is a graduate gemologist (GG GIA) and Registered Master Valuer.

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