Like snowflakes and fingerprints, no two diamonds are exactly alike. Until the mid 20th century, no standards were agreed upon based on which diamonds could be evaluated. GIA (Gemological Institute of America) established the 1st standard for describing diamonds, which is today accepted globally. The standard refers to the cut, colour, clarity, and carat weight of diamonds or the so-called 4 Cs of diamond quality.
The diamond 4 Cs is a universal language that helps communicate diamond quality and makes it more convenient for customers to purchase the gem.
That grade of diamonds refers to the 4 Cs: cut, colour, clarity, and carat weight. Each “C” is characterised by its own grading scale for assessing diamond quality. These four important factors help diamond sellers decide on the price of the gem and draw a parallel between different types of diamonds. The 4 Cs are also useful for customers as they make it easy and simple to purchase diamond jewellery.
Cut is the most important factor with regard to diamond quality. It counts for the brilliance and sparkle of the gem. Diamonds’ cut grade doesn’t refer to a diamond’s shape like oval, round, etc. It has to do with the stone’s proportions, polish, and symmetry and shows how well a diamond’s facets interact with light. Cut is the most technically complex “C” to analyse and quantify and is responsible for the overall beauty and value of the gem.
Well-calculated proportions and crafted precision result in the fascinating flashes of coloured light dispersion. Diamond images based on light performance data indicate what super ideal cut diamonds should look like. The ASET (Angular Spectrum Evaluation Tool) and Idealscope images show a gem with supreme optical performance. If facets are aligned to each other with excellent precision, the image will be symmetrical. The easiest way to identify precision cut is through the Hearts Patterning. It displays any slight variations or deviations as distortions.
GIA determines the cut grade of the standard round brilliant diamond by calculating the proportions of those facets that make up the diamond’s face-up appearance. Based on these proportions, GIA evaluates how well a diamond interacts with light. Such interaction results in the following visual effects:
- Brightness when the internal and external white light gets reflected from a diamond
- Fire or the white light scattering through the diamond to create all the colours of the rainbow
- Scintillation or the amount of sparkle produced by diamonds, and the light and dark area patterns caused by reflections within diamonds
Diamond cuts are usually assessed as:
- Ideal or Near Ideal when the angles and proportions of a diamond make it produce ultimate brightness, fire, and scintillation
- Very good
ACA (A Cut Above) diamonds might cost more than a generic GIA triple excellent or AGS (American Gem Society) triple ideal gem. There is a reason why these branded diamonds cost 10-15% more than other diamonds with the similar grading. To get the required proportions for a super ideal diamond, more skilled craftsmanship and rough material are used for polishing, which cannot be said about GIA’s triple excellent grading.
Colour is the second most significant grade after the cut as the human eye detects sparkle first and colour second. According to GIA, the diamond colour evaluation of the majority of gem-quality diamonds is based on the absence of colour.
Diamonds that are chemically pure and have no structural irregularities are perfectly transparent featuring no hues or colour. In fact, almost all gem-sized natural diamonds have some irregularities. The colour of a diamond may be the result of chemical impurities or structural irregularities in the crystal lattice. The latter refers to the symmetrical three-dimensional arrangement of atoms inside a crystal.
Diamonds that have no colour are the rarest. D-to-Z colour grading scale set by GIA is the most widely accepted system in the industry. The letter “D” stands for colourless diamonds. With increasing presence of colour, the scale continues to the letter “Z.” Even though colour distinctions may be subtle and seem to be invisible, they count for a significant difference when it comes to diamonds’ quality and price. All D-Z diamonds are regarded as white.
GIA Colour Scale:
- D – F – Colourless
- G – J – Near Colourless
- K – M – Faint Colour
- N – R – Very Light Colour
- S – Z – Light Colour
The hue and intensity of a diamond’s colouration make a diamond be more or less valuable. The less body colour is present in a white diamond, the more true colour will be reflected and a greater value it will have. For example, yellow hue detected in white diamonds lowers the price, unlike intense blue or pink diamonds that can be much more valuable.
Diamonds are available in various colours such as black, blue, brown, green, orange, pink, purple, red, steel grey, and yellow. There is a separate grading scale for these true fancy coloured diamonds. Red diamonds are the rarest coloured diamonds.
Clarity is the third most significant characteristic of the 4 Cs. The point is that most imperfections cannot be detected without professional magnification. According to GIA, diamond clarity is associated with the absence of inclusions and blemishes. Natural diamonds appear when carbon is exposed to extreme heat and pressure deep in the earth. Inclusions (internal characteristics) and blemishes (external characteristics) are the result of this process.
Diamond clarity evaluation is based on the determination of the nature, size, number, relief, and position of the mentioned characteristics. Also, it implies how these characteristics affect the overall appearance of a diamond. In fact, no diamond is perfectly pure. However, the purer it is, the higher its value.
GIA Diamond Clarity Scale:
- Flawless (FL) – No inclusions or blemishes are visible under 10x magnification
- Internally Flawless (IF) – No inclusions are visible under 10x magnification
- Very, Very Slightly Included (VVS1 and VVS2) – Slight inclusions that are difficult for a skilled grader to see under 10x magnification
- Very Slightly Included (VS1 and VS2) – Inclusions are noticeable with effort under 10x magnification, but are characterised as minor
- Slightly Included (SI1 and SI2) – Inclusions can be observed under 10x magnification
- Included (I1, I2, and I3)
Grades VVSI-SI1 are also known as eye-clean diamonds. Many inclusions and blemishes are so tiny that only a trained diamond grader can see them. If you look at a VS1 and an SI2 diamond with a naked eye, they may seem exactly the same. In fact, these diamonds are quite different with regard to overall quality. So it is highly important to consider expert and accurate evaluation of diamond clarity.
Diamonds containing significant inclusions or blemishes have less brilliance because these “birthmarks” interfere with the path of light through the diamond. Diamond cutters do their best to cut a gem so that inclusions are not observed through the table of the finished diamond. The best position for inclusions is under the bezel facets or near the girdle where they are difficult to notice.
Diamond Carat Weight
Diamonds are weighed in metric carats. Carat (ct) is the unit of measurement, which is used to describe the weight of diamonds and doesn’t refer to their size. “Carat” shouldn’t be confused with “karat”, which refers to gold purity. The word “carat” originated from “carob” seed, which was the unit of measure for diamond traders. As for “carat total weight” (ctw), it is used to measure the total weight of all diamonds in a jewellery piece.
1 carat is equal to 200 milligrams, or 0.2 grams (0.007 ounces). Carat weight can also be expressed in points or fractions, allowing for very precise measurements. 1 can be subdivided into 100 points. For example, a diamond that weighs 0.25 carats (below 1 carat) can be described as “twenty-five pointer.” A diamond that weighs more than 1 carat (e.g. 1.08 carat) can be expressed in carats and decimals (one point 0 eight carats).
The larger the diamond, the rarer, more desirable and expensive it is. However, two diamonds with the same carat weight can have very different values and prices because of the other three factors – cut, colour, and clarity. Carat weight is the most objective “C.”
Buying diamond jewellery does not have to be a complicated experience. Take time to understand the diamond 4 Cs so to be able to use them to your advantage. Learning how to properly evaluate diamond quality and value, you’ll know how to prioritise one over the other to make the right choice from among all the available diamond jewellery.