The term 4Cs we know today had its start in the early 1940s, as the brainchild of GIA founder Robert M. Shipley. A former retail jeweler, Shipley was fiercely committed to professionalizing the American jewelry industry. He established an institute (GIA) to provide jewelers with formal training and was a tireless advocate for greater knowledge, ethics and standards when it came to buying and selling gems.

Robert M. Shipley founded the Gemological Institute of America in 1931. Photo: GIA

Shipley developed the 4Cs as a mnemonic device to help his students remember the four factors that characterize a faceted diamond: color, clarity, cut and carat weight. The concept was simple, but revolutionary.

Throughout history, diamond merchants used a variety of different, usually broad, terms to talk about these four factors, rarely with any consistency. Terms such as river or water were used to describe diamonds that were the most colorless, with Cape assigned to pale yellow diamonds from South Africa’s Cape of Good Hope region. To describe clarity, they referred to diamonds as being “without flaws” or “with imperfections.” Cut was described as “made well” or “made poorly.” As a result, it was very difficult for jewelers to communicate those elements of value to their customers or for their customers to remember them. Only the term carat to describe weight has been used consistently from the 1500s to today.

Under Shipley’s direction, the term 4Cs became part of the American gem industry’s vernacular, popularized through advertising campaigns, lectures and GIA education courses. Within decades, they were integrated into the international nomenclature as well.

The 4Cs and the Diamond Grading Scales

Jewelers welcomed Shipley’s innovation, but GIA did not stop there. Shipley’s successor as president, Richard T. Liddicoat (affectionately known as “RTL” by later generations of GIA staff) – along with colleagues Lester Benson, Joseph Phillips, Robert Crowningshield and Bert Krashes – expanded on the 4Cs.

Richard T. Liddicoat, president of GIA from 1952 to 1983, integrated the 4Cs into GIA’s curriculum and laboratory reports. Courtesy: Norman B. Samuels Portrait Photographers, Los Angeles

Their work included not only development of the now famous GIA D-to-Z Color Scale and GIA Clarity Scale for diamonds, but also the scientific methods and procedures for objectively grading a diamond’s quality.

A 2.78 carat (ct) D-color round brilliant diamond that is internally flawless is a wonder of nature. GIA invented the color- and clarity-grading terminology that is now used internationally to describe diamond quality. Photo: Robert Weldon/GIA. Courtesy: Rogel & Co. Inc.

Color: The GIA D-to-Z Color Scale

Before the 4Cs and RTL’s contributions, a confusing alphabet soup was used to describe a diamond’s color. In communicating color quality to consumers, retailers used competing systems with descriptors like “A,” “AA” and “AAA.” There was virtually no agreement among firms as to what was considered an “A” grade. Most diamond wholesalers used terms like rarest white and top Wesselton, in addition to those mentioned above. In short, there were no standards that allowed for consistent evaluation and comparison.

Since the 1930s, GIA had been working on an accurate, objective color-grading system for colorless to light yellow diamonds. The goal was to develop a system based on absolutes, instead of relative terms and vague descriptions. In 1953, GIA, under RTL’s direction, introduced the GIA D-to-Z color scale, choosing the letter “D” for the top grade (colorless) precisely because the letter had negative associations and so was unlikely to be misinterpreted or misused.

GIA’s D-to-Z Color Scale is the industry standard for grading the color of colorless to light yellow diamonds.

In addition to establishing a color scale, RTL and his colleagues defined the methods that would be used to grade a diamond’s color accurately and consistently. These included determining the type of lighting and neutral background with which a diamond should be evaluated, prescribing precisely how the diamond should be held and viewed, and developing master stones: sets of diamonds of predetermined color value against which the subject diamond is carefully compared.

The D-to-Z diamond color terminology RTL and his colleagues pioneered is now used around the world, and strict color-grading procedures are followed by the GIA laboratory.

Understanding the 4Cs is essential if you’re shopping for a diamond engagement ring. This one has a 1 ct center stone surrounded by four diamond side stones. Melee diamonds in a halo setting frame the design and continue down the shoulders of the ring. Courtesy: Sylvie Collection

The GIA Clarity Scale contains 11 grades that range from Flawless (FL) to Included (I3).

Clarity:  The GIA Diamond Clarity Scale – Flawless to I₃

Diamond clarity grading was another area that was plagued by inconsistencies in terminology and methods. Some trade professionals used terms like perfect in addition to without flaws and with imperfections, which were vague and imprecise. Others used terms we recognize today, such as VS, VVS, and included, but without any agreed-upon definitions.  RTL and Benson used these terms in creating a clarity-grading scale, but defined precise categories and expanded the number of grades within each category to account for the array of diamonds in the market. Fine-tuned in subsequent years, the GIA Clarity Scale today consists of six categories ranging from Flawless to Included and contains 11 specific grades.

This precision in clarity grading was made possible by another GIA innovation: the introduction of the gemological microscope as a tool for clarity grading. Using the microscope, GIA graders plot the inclusions and blemishes in all diamonds for which a full GIA Diamond Grading Report has been requested.

A plotting diagram, a feature of all GIA Diamond Grading Reports, uses specific symbols to map a diamond’s various inclusions and blemishes.

Cut: Evaluating a Diamond’s Interaction with Light

The impact of Cut – how well a diamond interacts with light – was another attribute that RTL and his associates wanted to better explain and standardize. Originally, RTL turned to the work of Belgian mathematician and diamond cutter Marcel Tolkowsky to help determine “ideal” proportions for a round brilliant cut diamond. RTL’s contribution included a rating system with deductions for proportions that deviated from those.

Because of GIA’s efforts to standardize the evaluation of diamond cut, round brilliants such as these can now be objectively graded. Courtesy: Supreme Jewelry

GIA’s system for evaluating cut has been modified over the decades. In 2006, after years of extensive research that included advanced computer modeling and observational studies, GIA introduced the GIA cut grading system for round brilliant cut diamonds. Today, the GIA Cut Scale, ranging from Excellent to Poor, describes how successfully a diamond interacts with light to deliver the brightness, fire and scintillation we associate with a fine round brilliant.

The GIA Cut Scale assesses the overall cut quality of each diamond individually, taking into account such features as proportions, table size, polish and symmetry.

Many factors contribute to the evaluation of a diamond’s cut, including the size of the facets, girdle thickness and total depth.

More than the 4Cs: The World Standard

Using the latest scientific advances to establish grading standards that provide consistent, repeatable results, GIA has revolutionized the jewelry industry. With the framework provided by the 4Cs, it has transformed the way diamond quality is determined and communicated and, ultimately, how diamonds are bought and sold.

These standards are strictly followed by the GIA laboratory in its nine locations worldwide. They allow GIA to deliver objective, consistent diamond grading results anywhere in the world. It is important to note that although the terminology introduced by GIA has been adopted by other laboratories worldwide, only the GIA laboratory has the proprietary equipment and procedures to grade diamonds to these standards.

All this critical information becomes part of a GIA Diamond Grading Report. With it, you’ll know the essential facts about the diamond you’re considering.

The GIA Diamond Grading System provides a complete description of diamonds such as this 1.37 ct H-color, VS1-clarity round brilliant in a platinum Tiffany & Co. setting. Courtesy: 1stdibs.com

Why ask for a GIA Diamond Grading Report? Read more and decide for yourself.

What Is a Real Diamond?

It’s unlikely that you’ll hear a professionally trained gemologist call a diamond a real diamond, or use the word “real” to describe any material. If you want to come across as a smart shopper, you’ll need to rephrase the question.

For decades, diamonds have been the gem of choice for engagement rings. But with the advent of synthetic diamonds and diamond simulants, it’s only natural to ask about real diamonds. “Real” is not a gemological term. But to the consumer, it’s an important one.

A Diamond Is a Diamond Is a Diamond

From a gem professional’s point of view, a diamond is a diamond if it has a characteristic chemical composition and crystal structure. Diamond is composed almost entirely of a single element: carbon. It forms under conditions of high temperature and pressure that cause its carbon atoms to bond in essentially the same way in all directions. Another mineral, graphite, also contains only carbon, but its formation process and crystal structure are very different. The result is that graphite is so soft that you can write with it, while diamond is so hard that you can only scratch it with another diamond.

This definition of diamond applies to diamonds that come from the earth, as well as those that are created in a laboratory. It does not apply to other materials that might masquerade as diamonds.

So, when you ask a jeweler for a real diamond, you could be asking for a diamond created by nature or one created in a lab – since both materials qualify as diamond. Reputable jewelers avoid the term “real” altogether and, following U.S. Federal Trade Commission (FTC) guidelines, clearly distinguish between natural diamonds, synthetic diamonds and diamond simulants (or imitations).

In other posts we explain synthetic diamonds and diamond imitations. Here, we’ll dig a little deeper into natural diamonds and their incredible journey from deep below the earth’s surface to the engagement ring worn by your loved one.

A Brief Description of a Natural Diamond

Natural diamonds are one of nature’s wonders. Billions of years old, they formed deep in the earth’s mantle and were brought to the surface by volcanic eruptions. Two types of magma, kimberlite and lamproite, sometimes carried diamond rough with them. The magma quickly solidified into a diamond-bearing kimberlite or lamproite pipe.

A craton is an ancient, deep and stable portion of a continent. Its high heat and pressure provide the right conditions for diamond formation. Conditions under a craton are also stable enough to preserve diamonds for hundreds of millions of years after formation. Illustration: Peter Johnston/GIA

Most of the world’s diamonds are found in kimberlite, but the famed Argyle mine in Australia–once the world’s leading diamond producer– is a lamproite deposit. Major companies recover the diamonds by digging large open-pit mines to find the buried treasures. Over time, as the typically cone-shaped pipes narrow down, the companies switch to underground mining to capture the last of the diamonds.

Some diamonds end up in rivers, streams and even the ocean after forces of erosion released the crystals from their host rocks and gradually washed them into bodies of water. When diamonds are found this way, it’s called alluvial mining – a process of digging and sifting through mud, sand and gravel. While river sediments are often worked by small-scale miners using rudimentary techniques, large boats are used to scour the ocean sands off the coast of Namibia in search of fine diamonds.

Natural diamond rough is often shaped like an octahedron. Photo: Robert Weldon/GIA. Courtesy: Fusion Alternatives

For most of recorded history, the extreme scarcity of diamonds made them available only to the elite. In fact, up until 1730, the Golconda region of southern India and the Pacific island of Borneo were the only known diamond-producing regions in the world. Then diamonds were discovered in Brazil around the 1720s and a diamond ‘rush’ began. Soon, Brazil eclipsed India as the world’s top diamond producer, holding this title through the mid-1800s. With the discovery of large diamond-bearing kimberlite pipes in South Africa in the late 1860s, mining began on an industrial scale, increasing supply to meet broader consumer demand. Diamonds are now mined in several countries around the world, including Russia, Botswana and Canada, as well as South Africa and Australia. Learn more about where diamonds come from.

The face-up view of this diamond showcases the beauty of the round brilliant cut. Photo: Robert Weldon/GIA. Courtesy: Rogel & Col, Inc.

Turning Rough Diamonds into Polished Gems

The diamonds recovered have survived a brutal birth and then a rough ride to the earth’s surface. Diamond mining companies must remove a million parts of host rock to find one rough diamond. Workers then sort the rough diamonds into categories based on their size, shape, clarity and color. The mining company might cut a finished diamond out of the rough, or sell it to dealers and manufacturers.

Rough diamonds are often shipped to cutting centers in India, Israel, New York, Antwerp, China and Thailand. Highly skilled diamond cutters often use the latest technology, such as lasers, to transform the piece of rough into a highly polished faceted diamond. Most finished diamonds are sent to grading laboratories to determine their quality based on the GIA 4Cs standard: color, clarity, cut and carat weight. Every diamond will have unique qualities: no two will be identical.

A diamond cutter at Diacore Botswana examines the initial facets made on a fancy yellow diamond. Photo: Robert Weldon/GIA

Diamond Treatments

Some manufacturers may try to alter the color or clarity of a diamond to make it more appealing and marketable. The methods used to alter color range from crude ones like coloring girdle facets with a permanent marker, to more sophisticated ones like covering facets with an optical thin film, subjecting the diamond to radiation, or exposing it to high pressure, high temperature annealing. The most common clarity enhancement is fracture filling. All of these may improve the appearance of the diamond, but the seller is legally bound by the FTC to disclose that the diamond has been treated.

This diamond has been fractured filled to make it more attractive. Photo: Shane F. McClure/GIA.

This 1.05 ct diamond owed its apparent Fancy Light brown-pink color (left) to a coating. After the coating was removed by acid cleaning, the diamond was given a color grade of J (right). Photo: Jian Xin (Jae) Liao/GIA

Given their timelessness, resilience and durability, is it any wonder so many choose ”real” diamonds as a symbol of love and commitment? If you’re considering a natural diamond for an engagement ring, be sure to ask for a GIA Diamond Grading Report . The report is your proof that the diamond is natural and that its quality is what the seller describes, giving you the important information you need to make your purchase with confidence. And if you opt for a lab-grown diamond, a GIA Synthetic Diamond Grading Report is your assurance that the material is actually diamond and not an imitation.

Have you ever wondered about do-it-yourself tests to determine whether a specific gem is natural, synthetic or something else? Our post, How to Tell if a Diamond is Real, decodes the most common myths about such tests and why they don’t work.