A History of Diamond Grading

Diamond sellers in the 1800s shaped the system used today to grade diamonds. We look at how that system evolved to meet the needs of the industry.

Throughout history, diamond sellers have sought a way to determine a diamond’s value based on its color or absence of color. But methods and nomenclature were not clearly defined or consistently applied.

By the nineteenth century, daylight had become the basis for identifying a diamond’s color. In the late 1800s in lower Manhattan, then New York City’s diamond district, neighborhood buildings were painted yellow and faced the windows from which the dealers judged color in the north daylight.

By the early twentieth century, minimal standards for color grading were established, which set the time for grading between 10 a.m. and 2 p.m. only in an unobstructed good north light and always at the same location.

Variations

Terminology to describe color also varied greatly. Given that many of the diamonds were found in South Africa, descriptors could be traced to the mines or the country’s geographical regions. Jager was used for blue-white diamonds like those found in the Jagersfontein mine. Pale yellow diamonds were known as Cape for the Cape of Good Hope region. Still other names had their origins in nature; many alluvial diamonds were referred to as River or First Water.

All that changed in the early 1950s when the Gemological Institute of America (GIA) introduced its D to Z color grading system, which has become the benchmark for standardized diamond grading. History was then made in 1955, when the first GIA grading report was issued.

Recognizing the importance of setting objective standards, the GIA, along with the American Gem Society (AGS), began working on color grading standards in the 1930s.

In 1941, GIA founder Robert Shipley and Richard Liddicoat, who succeeded him as executive director in 1952, introduced the GIA Colorimeter. It was developed to select master stones by visually comparing a diamond to a repeatable standard called the “color yardstick,” a graduated wedge of glass that transitioned from colorless to yellow.

When a diamond being graded matched a section of the wedge in the colorimeter, the corresponding Roman numeral expressed the grade.

Standardization

In addition to consistent lighting, the grading system’s standardization is dependent on the use of a master set of comparison stones. The GIA master stones represent the highest point in their respective grade range. In order to differentiate its system from others that used A, AA or AAA, the GIA system began with the letter D.

Other organizations have also addressed the grading issue from their own perspective. In 1966, the AGS devised a numerical system, restricted to its members, that started at 0, which would be equivalent to a D, inching down in half-point increments to 2 for H and 4 for L, culminating in 10 for grades X-Z.

Since 1953, when Liddicoat first taught the system to jewelers, the GIA grading system has continued to evolve and improve. But the three factors first introduced more than 60 years ago – lighting, viewing geography and comparison standards – still form the foundation of this standardized diamond-grading system.

Image: IIDGR