GIA Diamond Certification

You might be surprised to learn that a ‘GIA certificate’ doesn’t really certify anything. It’s a widely used nickname for a grading report issued by the Gemological Institute of America (GIA). The oldest organization of its kind, many people consider GIA the world’s foremost authority on natural diamonds and gemstones.

PriceScope Pointer: A diamond grading report establishes the diamond’s all-important value-setting 4Cs. If a diamond is over graded you’ll overpay, so it’s important to choose a laboratory with a diamond grading process which follows strict, international standards.

Before going on: Check out the PriceScope Diamond Buying Guide

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GIA Diamond Certification Explained

A GIA grading report provides the gemological information needed to establish a diamond’s value. 

Fancy Shapes receive grades for 3 Cs

Diamond shapes other than round receive grades for three of the diamond “Cs” – carat weight, color and clarity, along with ratings for polish and symmetry (subsets of cut) and fluorescence. 

Full fancy shape reports also have limited proportions information as well as plots mapping the location of clarity characteristics in the diamond’s crown and pavilion. Smaller Diamond Dossier reports do not include this information.

GIA certification for 1 carat brilliant pear shaped diamond with vs 1 clarity grade

Round Brilliant Diamonds receive grades for 4Cs

In addition to all of the components above, round brilliant diamonds receive an additional grade for cut quality.

Full round brilliant reports also include proportions information as well as plots mapping the location of clarity characteristics in the diamond’s crown and pavilion of the diamond. Smaller Diamond Dossier reports do not include this information.

GIA certification for 1 carat round brilliant shaped diamond with excellent cut grade and f color grade

Why aren’t fancy shapes given a grade for cut?

The way light behaves in a round diamond can be determined using several key measurements, or proportions. Their geometry is simple, so rounds with matching key proportions reliably have identical light behavior. GIA had humans perform observational studies on a wide range of diamonds. Now they correlate those visual results with a round diamond’s proportions and assign a grade.

Fancy shapes are more complex. Even within the same shape, two diamonds can have a variety of different tiers of facets and ratios. This means two princess cuts (for example) with matching key proportions can have different light behavior. 

This is why GIA does not assign a cut grade to fancy shapes; unlike round diamonds their visual results cannot be correlated with proportions.


GIA Grading Report Formats

In addition to the well-known full Diamond Grading Report examples shown above GIA certificates are issued in a variety of formats for gemstones ranging from natural and lab grown diamonds to colored gemstones and pearls.

Can I send a diamond or gemstone to GIA?

Yes. Consumers can submit their own diamonds and gemstones to GIA. Options include submission through a local jeweler, shipping the gemstone directly to GIA or dropping off the gemstone at one of GIA’s 16 locations in 11 countries.

You can submit a gem to GIA here. 


Is GIA the Best?

The world’s most recognized diamond grading institutes are GIA, with 11 grading locations and 8 schools of gemology, and the International Gemological Institute (IGI), with 20 grading locations and 14 schools of gemology. 

In the United States the American Gem Society (AGS) and Gem Certification and Assurance Lab (GCAL) are also widely recognized. 

These four institutes have much in common, but also specialize in different areas. You can get information on all of them on PriceScope’s education page covering Diamond Certification.


The GIA Story

The GIA is widely considered the world’s foremost authority on diamonds, colored stones, and pearls. A public benefit, nonprofit institute, the GIA is the leading source of knowledge, standards, and education in gems and jewelry. As the oldest and most widely recognized gemological institute, the GIA has long set the standards by which other laboratories are measured.

Diamond and Gemstone Grading

In 1931 Robert Shipley established the GIA, opening the first U.S. based gemology correspondence course. By the 1940s Shipley introduced the Diamond 4Cs and developed the International Diamond Grading System (IDGS), which remains the worldwide standard for evaluating diamond quality. He was soon joined by Richard T. Liddicoat, a man who would become known as the ‘father of modern gemology.’ 

Shipley, Liddicoat and Robert Crowningshield, who joined GIA in 1947, created new approaches and equipment for analyzing diamonds and gemstones and established a school of gemology with a robust curriculum. The first GIA Graduate Gemologist diploma was issued in 1948.

GIA diamond certificates were first issued in 1953. They quickly became an international benchmark. The 4Cs developed by GIA and their IDGS have been adopted by every major gemological institute established since.

Vetted vendors, like Whiteflash, Blue Nile, and James Allen, offer comprehensive inventories of quality diamonds, complete with high-resolution images and accompanied by diamond gradings and certificates from GIA and other respected labs. These jewelers, with their ongoing commitment to transparency, ensure you won’t be disappointed with their diamonds.


GIA operates eight schools of gemology around the world. The majority of jewelry professionals in the USA who have studied gemology did it with GIA.  The Graduate Gemologist (GG) diploma, which focuses on gem grading and identification, is the institute’s highest professional credential. Other GIA program and course options include the Graduate Jeweler program, Jewelry Design & Technology program, and Applied Jewelry Professional program, among others.

Gemological institute of America sign on the robert mouawad campus in Carlsbad, California

What Else?

GIA has a well-organized Alumni Association. Their various chapters around the world host virtual and in-person events and connect members for the purpose of collaboration. 

Gems & Gemology is a quarterly scientific journal published by the Gemological Institute of America. Each issue is devoted to research on diamonds, gemstones, and pearls. Topics include geographic sources, imitations and synthetics, treatments, and identification techniques.


The GIA Bribery Scandal

In 2005 a diamond dealer raised allegations that GIA lab workers had accepted bribes to over-grade diamonds, artificially increasing their value. This led to an internal probe which ran for four months. The probe ultimately found evidence that certain laboratory workers had been in contact with clients, violating the GIA code of ethics, and that fraudulent grades had indeed been issued. 

The probe concluded with the resignation of four laboratory workers and the head of the laboratory. Several months later GIA’s president of 20 years resigned as well, though he was not named or implicated in the allegations.


How Does GIA Grade Diamonds?

The process of diamond grading is largely uniform among the major gemological institutes. See PriceScope’s education page Diamond Grading Explained to learn about the strict sequence of intake, analysis and reporting. 

Gemological institute of America (gia) grading lab expert looking at diamond under microscope


Is GIA Better or Worse Than Others?


GIA is considered by many to be the world’s foremost authority in loose natural diamonds and gemstones. The world’s most valuable and recognized natural diamonds, sold by auction houses, frequently come with GIA grading reports. GIA will always enjoy a position of prominence because they established the standards other laboratories now use. 

Their schools of gemology are highly regarded, especially in the United States, where the vast majority of trained jewelry professionals received their training from the GIA.

In recent years, online shopping for diamonds and jewelry has changed shopping habits and has proven to be a great benefit to buyers. By being able to select a certified loose diamond from a wide selection and pair it with a beautiful setting, you open up a whole world of possibilities.

Vendors like Whiteflash and James Allen are professionals at listening and advising you on which combo of the 4Cs is optimal for you and your budget.

GIA and cut grading

Cut quality is considered by many to have the most influence on a diamond’s appearance. Cut quality assessment is of particular interest to members of PriceScope. This is logical for a community established to help new consumers find beautiful diamonds. It’s difficult to assess diamond brightness, fire, and sparkle without seeing the diamond in person, so a cut grading system that reliably separates top performers from poor performers is desirable.

Unlike color and clarity grading, GIA’s cut grading system for round brilliant diamonds is notoriously loose. Nearly 70% of round diamonds they grade received the highest cut grade of “Excellent,” yet many of them have notable performance deficits.

Do you need a crash course on diamonds? The PriceScope Diamond Forums and PriceScope Education Center are excellent resources for diamond information. Discover all things diamonds right here to explore at your own pace, whether it's the 4Cs, specifications or certifications - we’re here to empower you to make better informed diamond purchases.


Only around 20% of GIA Excellent diamonds pass Holloway Cut Adviser analysis.


Statistically, a GIA Excellent diamond may be rated anywhere between AGS Ideal (AGS 0) and AGS 5 in performance, if graded using the AGS Platinum Report. To predict where a given GIA Excellent falls requires details of spread, proportions, and angles. But facet-group data is averaged and further rounded up or down, so definitive predictions aren’t possible. Moreover, no measure or analysis of 3D optical precision is provided. In general terms the proportions most frequently used producers submitting diamonds to GIA correlate to AGS 2-4, and sometimes AGS 5 in performance, because those cutting angles produces a heavier diamond.

GIA color and clarity grading

GIA’s color and clarity grading are considered by many to be the best in the industry. Of course, diamond grading is subjective, especially in the areas of color and clarity. To keep diamond grading consistent, GIA uses calibrated master color stone-sets and uniform clarity standards to ensure a baseline of uniformity. 

Nevertheless, a diamond that falls directly on the border of two grades may come out on one side of the other, depending on the subjective opinion of the GIA gemologist making the judgment. Diamond grading also becomes very granular at the high end of the color and clarity scales. Across GIA’s 11 locations it’s also possible that some will be stricter than others, week to week and month to month.

Diamond Grading and Standard Deviation

Whether it’s GIA certification, or grading done elsewhere, due to the subjective nature of grading a standard deviation of +/- one grade is frequently deemed acceptable among professionals in the diamond grading industry.

This is perfectly logical from an analytic standpoint. At point of sale, however, a difference of +/- one grade may have significant influence on value. For this reason, it’s important for a buyer and a seller to agree on whether GIA, IGI, AGS, GCAL or another lab will issue the document of authority prior to sale.

To fully understand our huge variety of diamonds, we suggest you check out our loose diamond selection, which has all the nitty gritty details you need, such as certifications, to feel confident about your purchase.

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