Until the middle of the twentieth century, there was no agreed-upon standard by which diamonds could be judged.
The Gemological Institute of America (GIA) created the first, and now globally accepted standard for describing diamonds: Color, Clarity, Cut, and Carat Weight.
Today, the Four Cs of Diamond Quality is the universal method for assessing the quality of any diamond, anywhere in the world.
The creation of the Four Cs meant two very important things: diamond quality could be communicated in a universal language, and diamond customers could now know exactly what they were about to purchase.
Diamond carat weight is the measurement of how much a diamond weighs. A metric “carat” is defined as 200 milligrams. Each carat can be subdivided into 100 ‘points.’ This allows very precise measurements to the hundredth decimal place.A jeweler may describe the weight of a diamond below one carat by its ‘points’ alone.
For instance, the jeweler may refer to a diamond that weighs 0.25 carats as a ‘twenty-five pointer.’ Diamond weights greater than one carat are expressed in carats and decimals.A 1.08 carat stone would be described as ‘one point oh eight carats.
All else being equal, diamond price increases with diamond carat weight, because larger diamonds are more rare and more desirable. However, two diamonds of equal carat weight can have very different values (and prices) depending on three other factors of the diamond 4Cs: Clarity, Color, and Cut. (for more on carat weight)
Diamond clarity refers to the absence of inclusions and blemishes. Natural diamonds are the result of carbon exposed to tremendous heat and pressure deep in the earth.
This process can result in a variety of internal characteristics called ‘inclusions’ and external characteristics called ‘blemishes. Evaluating diamond clarity involves determining the number, size, relief, nature, and position of these characteristics, as well as how these affect the overall appearance of the stone.
While no diamond is perfectly pure, the closer it comes, the higher its value. Many inclusions and blemishes are too tiny to be seen by anyone other than a trained diamond grader.
To the naked eye, a VS1 and an SI2 diamond may look exactly the same, but these diamonds are quite different in terms of overall quality. This is why expert and accurate assessment of diamond clarity is extremely important. (for more on clarity)
Diamond color actually means lack of color! The diamond color evaluation of most gem-quality diamonds is based on the absence of color. A chemically pure and structurally perfect diamond has no hue, like a drop of pure water, and consequently, a higher value.
GIA’s D-to-Z diamond color-grading system measures the degree of colorlessness by comparing a stone under controlled lighting and precise viewing conditions to masterstones stones of established color value. GIA’s diamond D-to-Z color-grading scale is the industry’s most widely accepted grading system.
The scale begins with the letter D, representing colorless, and continues, with increasing presence of color, to the letter Z. Many of these color distinctions are so subtle that they are invisible to the untrained eye; however, these distinctions make a very big difference in diamond quality and price. (for more on color-grade)
Diamonds are renowned for their ability to transmit light and sparkle so intensely. We often think of a diamond’s cut as shape (round, emerald, pear), but a diamond’s cut grade is really about how well a diamond’s facets interact with light.
Precise artistry and workmanship are required to fashion a stone so its proportions, symmetry, and polish deliver the magnificent return of light only possible in a diamond.
To determine the cut grade of the standard round brilliant diamond – the shape that dominates the majority of diamond jewelry – GIA calculates the proportions of those facets that influence the diamond’s face-up appearance. These proportions allow GIA to evaluate how successfully a diamond interacts with light to create desirable visual effects such as:
Brightness: Internal and external white light reflected from a diamond
Fire: The scattering of white light into all the colors of the rainbow
Scintillation: The amount of sparkle a diamond produces, and the pattern of light and dark areas caused by reflections within the diamond.
GIA’s diamond cut grade also takes into account the design and craftsmanship of the diamond, including its weight relative to its diameter, its girdle thickness (which affects its durability), the symmetry of its facet arrangement, and the quality of polish on those facets.
The GIA Diamond Cut Scale for standard round brilliant diamonds in the D-to-Z diamond color range contains 5 grades ranging from Excellent to Poor. (for more on cut-grade) Should you require a more comprehensive look at the Four Cs, we highly recommend these more in-depth articles on carat-weight, color, clarity, and cut.
We hope you found this article helpful in getting an overall sense of what determines the value and cost of a diamond. However, should you have any additional questions about this or any other jewellery related topics, you can always: “Ask Our Jeweller”
You may also enjoy this “interactive application on The Four Cs.“ Be sure to sign up for OUR NEWSLETTER to stay up-to-date on the latest jewelry developments, trends, diamonds, gems, watches, reviews, tips and more!