The 4 Cs (Cut, Clarity, Color and Carat) are the criteria that determine the value of a diamond and up until today they have become an integral part of the diamond trade. Those 4 quality criteria offer an internationally uniform system for grading diamonds, which offers transparency to customers and helps to prevent misunderstandings. Prior to the establishment of the 4 Cs as an international standard, the diamond industry was a mess of subjective evaluations, which also negatively impacted customer confidence. In this article, you will learn everything about the history and development of the 4 Cs.
Many paraphrases, only carat remains constant
As early as the 16th century, traders used different systems to describe the properties of diamonds. At that time, the four properties that we still evaluate today, namely cut, clarity, color and carat, were already used, but a uniform system was lacking. Instead, diamond dealers in different regions used different terms: for colorless diamonds, descriptions such as "river" or "water" were used; for diamonds with a yellow hue, terms such as "tint" or "tincture" were used. Later, scales were developed, for example, with different numbers of the letter A, i.e. "A", "AA", "AAA" etc. The numerical system was used to describe scales, but also the Roman numerals or short descriptions in words, such as "blue white" or "fine white". The purity was described with terms like "without flaws/imperfections" or "with flaws/imperfections", but again there was no standardized scale. Only the term carat was used at that time. However, it was not until 1907 that the unit carat was standardized at 0.2g/ct.
Often, the same terminology for grading diamonds was used within smaller regions, which is why communication in the diamond trade only became problematic when trading across regions.
Robert M. Shipley - Founder of the GIA and the 4 Cs
The US-American Robert M. Shipley actually began his career in the 1920s as a retail jeweler, but would later play a major role in setting international grading standards for diamonds. During a transaction with two of his best customers, they challenged his expertise: Shipley realized that he did not know as much about diamonds as he had previously believed. He also saw it as a general problem that there was no uniform training in the industry, and therefore many jewelers lacked the necessary expertise in handling gemstones. After losing his jewelry business in the mid-20s as a result of his divorce, he traveled to Europe for an extended period of time and educated himself on the subject of diamonds during that time. He took a correspondence course in gemology from the Great Britain National Association of Goldsmiths. Upon returning to the U.S., he wanted to share his newfound knowledge with others in the industry as a way to restore customer confidence in jewelers. He traveled the country giving training sessions imparting his knowledge, thus laying the foundation for the GIA. The Gemological Institute of America was officially founded in 1931 with the opening of the first gemological laboratory.
In the years that followed, Shipley sought a standardized system for grading diamonds and eventually introduced the 4 Cs as grading criteria. It is not precisely dated when the 4 Cs were officially introduced, but starting in the early 1940s, the term began to appear in newspaper articles and was used by people who had taken gemological courses with Shipley. The GIA's 4 Cs quickly became accepted as the international standard and remain the basis by which all established gemological laboratories worldwide grade diamonds.
The evolution of 'Cut'
One of the Cs, namely Cut, has undergone a longer evolution in grading from the 1940s to the present. It is only since 2006 that GIA reports have included a grade for Cut according to the criteria commonly used today. GIA had been researching diamond cut for decades when they made a major breakthrough in 1989 thanks to new computer technologies. With the help of computer-generated models, it was now possible to predict, in the case of round brilliant-cut diamonds, how the light behavior of the diamond must turn out with the corresponding proportions, i.e. how prominent brilliance and fire will be. It was now possible to precisely analyze the effects of the proportions of all the existing surfaces, but also the effects of the angles at which the surfaces are positioned in relation to each other.
With the advanced technological possibilities, the GIA now wanted to find out, on the one hand, how differences in proportions affect the viewer's visual perception of a diamond and, on the other hand, which combinations of certain proportions are judged by viewers to be visually appealing or unappealing.
The GIA surveyed several thousand test subjects, including diamond producers, jewelers and also consumers, on the appearance of over 2,300 diamonds. They were asked to give their verdict on brilliance, fire and the overall appearance of the cut to determine which types of cut were considered most attractive. In this way, it was possible to confirm that the computer models developed were accurate and consistent with what the normal viewer sees with the naked eye. It was possible to find out at what degree of variation in proportions the viewer notices a difference. Most importantly, it was possible to develop a grading system for the cut that is predictable. This means that if a certain combination of proportions is entered into the system to determine the cut's rating, then this computer-generated rating will also match the cut grade that a majority of potential viewers would give for the diamond in question.
The 4 Cs were established by the GIA, but are now used - and also further developed - by all major gemological laboratories to grade diamonds. In January, for example, we reported that the International Gemological Institute (IGI) has introduced a new cut grade for so-called fancy shapes in its reports. Previously, it was difficult to evaluate the cut of fancy shapes, as it was not possible to reliably predict the light behavior as is the case with uniformly round brilliant-cut diamonds. You can read our news article on the subject here. So you can see that the 4 Cs with their meanwhile about 80 years of history do not represent a deadlocked system, but are nevertheless further developed and adapted to modern demands and needs. They represent a grading system that evaluates all relevant characteristics of a diamond as accurately as possible, so that customers can rely on the grading when making their purchase decision and feel sufficiently informed.
Lab diamonds are also graded according to the 4 Cs, as they have the same physical, chemical, and optical properties as their counterpart from the mine. Therefore, since 2018, the Federal Trade Commission (FTC) has defined lab diamonds as real diamonds. The International Gemological Institute (IGI) was a pioneer in certifying lab-grown diamonds, having been grading lab-grown diamonds there since 2005. At the time, lab-grown diamonds were still causing a lot of uncertainty in the industry, and the IGI was the first to provide a degree of security and comparability in this new, fast-growing branch of the diamond industry. If you would like to learn more about laboratory diamond certification, feel free to read our blog post on the subject.
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