Beautiful. Rare. Cherished. Each diamond is unique and is a miracle of time, place and change. And each has specific qualities that establish its value.
Until the middle of the twentieth century, there was no agreed-upon standard by which diamonds could be judged. GIA created the first, and now globally accepted standard for describing diamonds: Color, Clarity, Cut and Carat Weight. Today, the 4Cs of Diamond Quality is the universal method for assessing the quality of any diamond, anywhere in the world. The creation of the Diamond 4Cs 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.
As creator of the Diamond 4Cs and the International Diamond Grading System™, GIA is not only a global authority, but the world’s trusted source for unbiased assessment.
Colour & Clarity
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 of established color value.
Many of these diamond 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.
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.
Diamonds are renowned for their ability to transmit light and sparkle so intensely. We often think of a diamond’s cut as shape (round, heart, oval, marquise, 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.
A diamond’s cut is crucial to the stone’s final beauty and value. And of all the diamond 4Cs, it is the most complex and technically difficult to analyze.
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
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. But 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.
It’s important to remember that a diamond’s value is determined using all of the 4Cs, not just carat weight.