GIA 4Cs OF DIAMOND GRADING

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. 

Did you know we offer our Clients a Complimentary Diamond Grading Crash Class? Feel free to contact us so we can explain the 4Cs to you in person!

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CUT
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A lot of people may not be aware, but Cut Grading is the most important diamond grading to ensure a Diamond's brilliance. If a diamond is cut poorly, it will appear dull even if it has a high color and clarity grade.

Diamonds are renowned for their ability to transmit light and sparkle so intensely, so diamond cut actually means 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.

 

Video by Tiffany & Co.

Achieving the best cut for a diamond reflects in 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 what the best cut for a diamond is, by studying 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.

 

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CARAT
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Diamond carat weight measures how much a diamond weighs. Each carat is 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. 

 

Diamond price increases with diamond carat weight because larger diamonds are rarer 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: Color, Clarity, and Cut. While now you know what carat means, it’s also important to remember that a diamond’s value is determined using all of the 4Cs, and not just carat weight.

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COLOUR
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Understanding what diamond color means helps in choosing the right diamond. Interestingly, the diamond color evaluation of most gem-quality diamonds is based on the absence of color. 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. Hence, it is important to get a GIA expert’s opinion in evaluating the best color for your diamond.

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CLARITY
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To understand diamond clarity, we must first understand how diamonds are created. 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. If you are trying to determine what is the best clarity for a diamond, remember that no diamond is perfectly pure. But the closer it comes to purity, the better its clarity.

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The GIA Diamond Clarity Scale has 6 categories, some of which are divided, for a total of 11 specific grades:

  • Flawless (FL) No inclusions and no blemishes visible under 10x magnification

  • Internally Flawless (IF) No inclusions visible under 10x magnification

  • Very, Very Slightly Included (VVS1 and VVS2) Inclusions so slight they are difficult for a skilled grader to see under 10x magnification

  • Very Slightly Included (VS1 and VS2) Inclusions are observed with effort under 10x magnification, but can be characterized as minor

  • Slightly Included (SI1 and SI2) Inclusions are noticeable under 10x magnification

  • Included (I1, I2, and I3) Inclusions are obvious under 10x magnification which may affect transparency and brilliance

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FLUORESCENCE
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Fluorescence is the glow you sometimes see when an object emits visible light. Some diamonds fluoresce when they are exposed to ultraviolet (UV) rays from sources like the sun and fluorescent lamps. This can cause them to emit a bluish light or more rarely, a yellow or orangy light. Once the UV light source is removed, the diamond stops fluorescing.

diamonds in the D to H color range with a bluish fluorescence are often considered less desirable by the trade. Some believe that a bluish fluorescence may cause a hazy or oily appearance in these diamonds, but only if the fluorescence intensity is very strong. Not all diamonds with very strong bluish fluorescence look oily, however, and they may sell for less than diamonds that do not have blue fluorescence.

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Diagrams & Text on this page have been provided by GIA