A Complete Guide to the Gemological Institute of America (GIA) Grading Certifications

If you have spent any time looking at diamonds or gemstones, you have probably heard the acronym GIA. The Gemological Institute of America with 3000 employees operating in 13 countries is the most widely known and widely respected organization in the world when it comes to diamonds and gemstones.
Founded in 1931 by Robert Shipley as a home-study correspondence course in gemology, GIA has grown to international prominence with campuses and laboratories spread all over the globe. GIA is a fountainhead of knowledge in the gem world conducting advanced research and training new generations of gemologists. They literally wrote the book on diamond grading. To learn more, read our article about the other top diamond certification labs.
Simon G. MR1394 Fabled Diamond Engagement Ring
Simon G. MR1394 Fabled Diamond Engagement Ring
In 1953 the first GIA laboratory was opened and diamond grading reports were born. The grading system that was created is still used in very much the same way almost seventy years later, and is the basis for grading done by all labs that have arisen since. With few exceptions the 4 C’s are still evaluated in the same way all over the world. GIA has had more influence over the modern world of gemstones and fine jewelry than any other organization that has ever existed.

Why is it important to buy a graded diamond?

First and foremost is to be sure it is what the seller represents it to be. You want to be sure it is a natural diamond and that the quality is commensurate with the price you are paying. It is always important to deal with a trustworthy seller, but if you are making a significant diamond purchase it is important that the diamond has a grading report from a reputable laboratory, commonly referred to as a certified diamond.

What is a GIA Diamond Grading Report?

GIA logo
Perhaps nothing that the GIA does today has as much riding on it financially as the GIA diamond grading report. In the last few decades lab grading of diamonds has become an expectation for any diamond of significance in the market. And while there are many different labs operating in the market today, GIA still dominates. This is especially true in larger, finer quality diamonds.
The basic GIA diamond report is essentially the same evaluation that GIA has been doing for decades. It involves carat weight and measurements, color and clarity grade, fluorescence, and additional comments. Larger stones will also have a stone plot which indicates location and type of internal and external features are present, at least those necessary to identify the stone and support the clarity grade.
GIA Certification
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Since 2005 a GIA report for round brilliant diamonds will also contain an overall cut grade. GIA uses the same scale they use for polish and symmetry. An overall cut grade of Excellent is the top grade. The GIA Triple Excellent has become a standard for a well cut stone; Excellent polish, Excellent symmetry, and Excellent overall cut grade.

What is the GIA diamond grade scale?

GIA developed the basic system of diamond grading (the 4C’s) that is used by laboratories all over the world. While there are some differences in certain aspects of grading between labs, color and clarity grades are essentially standardized.
GIA grades white diamonds on a D-Z scale, with D being totally colorless and Z being tinted to the point of crossing over into the Fancy color diamond range. DEF are considered the colorless range, while GHIJ are grades in the near colorless range. Grades K-Z have increasing amounts of body color.
GIA Color Scale
GIA Color Scale

GIA Dossier vs Full Diamond Report

For smaller stones (under 1.00 carat), GIA offers a scaled back report called a Dossier. It provides the same information as the full report with exception of the stone plot. In place of the stone plot, which helps to positively identify the diamond, a diamond with a dossier report will be laser inscribed on the girdle with the GIA logo and report number. It is also possible to order inscription on a full report.

What does the unique certificate number indicate?

This is a number that can be used to verify the details of the certificate, even if the hard copy is missing. This number is often inscribed on the girdle of the diamond as well, and should always be on the receipt from the vendor. The major laboratories have online ‘report check’ functionality that will enable a customer to type in the report number and pull up a copy of the certificate.

GIA Report Check

GIA has a report check feature to verify a diamond report. Simply type in the report number and a page of results will be presented with a link to download a PDF of the document. Other major labs also have this and other digital features.

GIA Facetware

GIA also provides a tool on their website to estimate an overall cut grade by plugging in parameters to their Facetware program. This is useful for understanding the probable GIA cut grade for diamonds without a GIA report or for diamonds with GIA reports that pre-date the introduction of their cut grading system (2005). Because the data would need to be verified and because polish and symmetry grades would have to be done by human graders, the facetware result is not a guarantee.
It should be noted that the GIA cut grading system is parameter-based, as opposed to the more rigorous and exacting light performance based AGS cut grading system. Though based upon extensive research on which sets of parameters make the best looking diamonds, the GIA system does not directly measure the components of light performance such as brightness, contrast, leakage, and fire. Instead, the parameters are compared to a table of predetermined parameter sets and the grade is pegged on where the parameters fall on that table.

GIA Report for Laboratory-Grown Diamonds

In the last few years synthetic diamonds have started to appear in the market in significant numbers. GIA and other major laboratories must have good screening systems in place in order for these man-made diamonds not to be mistaken for or misrepresented as natural Earth-mined diamonds. Because there is an emerging demand for lab-grown diamonds, GIA and other labs not only screen them but also issue grading reports on them. This enables a consumer to know qualitatively how their diamond compares to other diamonds in the market.
GIA Lab Grown Diamond Certification
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A GIA report for lab-grown diamonds is clearly distinctive from a report on a natural diamond, eliminating the possibility of misunderstanding. The diamond is also inscribed on the girdle as LABORATORY-GROWN. The report is structured similarly to a natural diamond report with color and clarity grades, measurements and stone plot. GIA is careful to point out that while color and clarity specification are described on the same scale as the GIA Diamond Grading Report for natural diamonds, they do not correlate to nature’s continuum of rarity. The lab-grown report is available as a digital report only.

GIA Gem Identification

For hundreds of years a dizzying array of imitation, and more recently, synthetic gemstones have become part of the jewelry landscape. From natural zircon and quartz imitating diamonds, to foil backed glass, to laboratory grown synthetics of all kinds, the jewelry world has seen an almost limitless variety of materials pretending to be natural gemstones. Also, for hundreds of years, but increasing with modern technology, natural gemstones have undergone a variety of treatments to improve their appearance. To protect consumers against misrepresentation and to instill confidence in the jewelry trade it was necessary to develop the tools and skills for jewelers to accurately identify gemstones. This is where GIA has really excelled.
Starting from the earliest days GIA developed tools and taught jewelers how to use them to evaluate gemstones. Over the years Gem Instruments, a division of GIA, has brought dozens of devices like the refractometer, polariscope and dichroscope to the market to make it easier to identify natural gemstones and separate the fakes. In recent years has developed sophisticated devices to separate natural from synthetic diamonds. Some of these instruments are marketed to the trade and some are developed as proprietary technologies to be used in GIA labs to assist in the identification and grading processes.
A GIA gem identification report will feature basic weights and measurements, a description of the shape and facet configuration, the mineral species and variety , indications of treatments or absence thereof, and geographic origin if requested and if knowable. Geographic origin determination is a relatively new service for GIA reports and derives from their extensive research and database of gemstone submissions over many years. It is only important in limited cases where a certain location may command a significant premium in the market such as Burma Rudy, Kashmir Sapphire, and Russian Alexandrite.

GIA Research

Since 1931 GIA has been a leader in diamond and gemstone research. Today the Institute employs a large team of PhD’s, scientists, and researchers studying a wide variety of topics in the field of gemology. This research is the basis for continuing to stay up to date with detection and identification of synthetics and new enhancement treatments, as well as developing new instruments. In addition, the research is enabling new services such as Origin Reports based upon data from the testing done on thousands of specimens studied over time.
In 1988 GIA graded the most famous diamond in the world, the Hope diamond. It was the first time the storied diamond had been graded by a high profile laboratory. The team of scientists from GIA were given unprecedented access to the priceless gem in a secure room at the Smithsonian where the priceless gem is housed. The team determined the color to be fancy dark grayish blue with a clarity of VS1. (the gem had long been purported to be flawless). Also revealed were details of the stone’s rare red phosphorescence.
The Gubelin Project is of particular note in this department. World renowned gemologist Dr. Edward J. Gubelin assemble a collection of 400 fine gemstone specimens from all over the world during his career. GIA has been able to do advanced testing on all samples in this collection and has assembled a comprehensive catalogue of datasheets and photographs of the entire collection.

GIA Instrument Development

From very early on GIA was developing instruments and tools for gemstone identification and evaluation. During the 1930’s GIA patented a jeweler’s loupe and a microscope. In recent years GIA has developed sophisticated equipment to detect synthetic diamonds. They also have developed proprietary equipment and methodologies to assist in diamond grading. They currently utilize proprietary color grading equipment to assign automated color grades to a limited subset of diamonds they grade, bypassing the need for human observation. In a recent GIA study on diamond fluorescence they mention that their bulk contrast methodology may one day be used in reporting on a diamond’s transparency, a factor that determines how well a diamond reflects and refracts light.
Their latest development is a small and portable device for separating natural from lab grown diamonds. The probe is small enough to test mounted diamonds down to .09mm in size. The ID100 device uses sophisticated fluorescent spectroscopy to make distinction in two seconds. If the diamond is natural it will register a “pass”. If it fails the diamond should be referred for further testing.

GIA Education

Since education was the first mission of GIA, it is no surprise that this is still a huge focus of the organization. They now have multiple locations worldwide where students can enroll in on-campus programs, as well as a comprehensive distance program that enables students to do self-paced study at home. All students must pass on-site diamond grading and gem identification labs in order to receive the more advanced credentials such as Diamonds Graduate and Graduate Gemologist. GIA and their sister organization The American Gem Society (AGS) collaborate on education with on-site GIA courses taught on the AGS campus in Las Vegas.
In addition to regular coursework, GIA also publishes a monthly magazine that contains the most up to date information on subjects of high interest. Gems and Gemology magazine was first published in 1937 and continues today. It is a way for gemology students and trade members to stay up-to-date on the latest news.
GIA also regularly publishes academic articles chronicling the work of their scientists and research staff on subjects such as diamond cut grading and the impacts of fluorescence on diamond appearance. The depth and breadth of GIA research has been a major factor in promoting an understanding of and consumer confidence in diamonds and gemstones for almost a century.

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