Beyond 4Cs: Going deeper into the study of Diamond Quality

Those who have spent any amount of time researching diamonds, especially in relation to the purchase of fine jewellery, would have encountered the 4Cs of Diamonds. The importance of the top four factors that are said to determine a diamond’s final quality: its clarity, colour, carat and cut is an ever-present element of this equation. However, these factors alone can only tell you so much about what determines a diamond’s real value. For precious diamonds, from the standpoint of their trade, usually finds themselves as a part of a jewellery item. Hence its value and other attributes are necessarily affected by the character and quality of other elements: Such as the shape of the diamond, the type and colour of the precious metal, accent stone, the presence of secondary gemstones etc. Depending on what the person is looking for: a pure diamond, or a fine jewellery piece or, interestingly a different type of diamond how the diamond’s value is measured may differ. This brings us to the business of coloured (fancy) diamonds, which raises a new set of questions on measuring diamond value.

The 4Cs of Diamonds: A Quick Recap

No discussions of diamond quality are worthwhile without knowledge of the 4Cs. The 4Cs of diamonds is the industry standard when it comes to the measure of these carbon-based precious stones. The carbon atomic structure of diamonds, which has been heavily studied by experts in the field, along with its other qualities, has led to a globally accepted measure. One that is given by the Gemological Institute of America (GIA). The 4Cs is an integral part of measuring diamond quality, thus no purchase of a diamond, either as a gemstone or as a part of a fine jewellery item should be done in the absence of their study. So here’s a quick breakdown of the 4Cs:


The quality of a diamond in relation to its colour is correlated to its absence: Meaning the ‘less’ colour that is present in diamonds the higher its perceived quality. Since the industry standard for quality, diamonds is determined by their colourless character; in reality, however, virtually all diamonds contain a varying shade of yellow-brown. A shade that is present at varying levels, with the higher levels of such colour tones being negatively correlated with diamond quality and value. One that has resulted in a diamond grading system that determines its value in relation to its colour (i.e. its absence). Diamonds in relation to their colour (i.e. absence) are graded by the GIA diamond colour scale: Which measures the quality of diamonds on a spectrum. Starting from D to Z: which goes from the colourless/very lower colour containing variety, starting from the (D-F) range, moving to the diamonds range which carries higher levels of colour. The greater the presence of colour the lower its value.


In diamonds, size does matter. This is a simple point, one that applies to all gemstones. The bigger the total size of a single stone the higher its value. The carat, which equals 0.2 grams is a key measure that is used to determine the value of diamonds since the greater the size of the gemstone, means that it is the better candidate for a more optimal cut. For the greater size stone will accentuate other natural attributes the diamond possesses: such as its ability to reflect light. As an example, one may know that in popular culture is that of people showcasing their big diamond engagement ring. With the quality of the stone being a reflection of its higher value. Carats are a key determinant in judging diamond value owing to the rarity of finding such large gemstones, especially those that score highly for other factors in the 4Cs.


The cut is where things get a bit tricky. When measuring diamond quality, the cut of the diamond is not to be confused with its shapes. Diamond shapes, which are well known in the industry, ranging from the popular Oval, Cushion, Princess, Emerald to other lesser-known shapes. The shape of the diamond relates to the physical outline of the precious stone. That can be considered as the external character of the gemstone. Diamonds cuts are interesting in that they relate to the shape of the diamond. For example, there is an Emerald diamond shape, which also correlates to a diamond’s cut (i.e. Emerald Cut). Popular diamond cuts are Princess, Brilliant. The cutting of diamonds is a science, that can only be handled by experts in the field. A key factor that is used to measure the quality of the cut is the diamond’s proportion: Which is the relationship between its ratio, size of the stone’s depth, width and table (the flat area on its surface). These proportions of the select stone play a key role in determining its value. Which is influenced by the quality of the cut. Note here, the quality of the diamond cut is not simply a question of the type of cut. But it is the ability of the diamond cut to be optimal enough to accentuate the other qualities of the stone. This means other factors that make up the 4C: Carat, Clarity, Colour need to be factored in. A great cut will optimize the glitter and glow of the diamond.


Diamond clarity is arguably the more complicated factor in measuring diamond quality. This is owing to the number of factors that work into measuring diamond value at this level. The diamond’s clarity fundamentally deals with the capacity of the gemstone to interact with light. From reflecting light to letting it light pass through it. Since the key draw, a precious diamond is its glitter, for in fine jewellery the ability of the diamond to sparkle is a key factor that sets it apart from other precious stones. So the transparency and light reflective qualities of the diamond are affected by a number of factors: inclusions, blemishes on the surface of the diamond etc. Inclusions, for the unknown, refers to the presence of minerals and other structures within the gemstone that affects its inner clarity. These can take a number of different forms, and range in size. The greater the number and/size of inclusions the lower quality of the diamond. Which presents a challenge for diamond cutters, who seek to balance a larger carat diamond with a high-quality cut. Diamond quality in terms of clarity is measured from Flawless (F) – to Included (I). With the former being the highest in quality.

Factors that Affect the 4 Cs in Fine Jewellery

The market for diamonds, in the consumer space, is driven mainly by the need for diamonds as gemstones for fine jewellery items. Fine jewellery is not mainly about the centre stone, if at all. Quality jewellery consists of a number of factors that determine its final quality. So in items that involve top-quality diamonds, their value is strengthened by the presence of other factors. Much of this comes down to the design of the item and the skill of the jeweller that goes into making it.

The Shape of the Diamond

As noted diamonds, in addition to their famous cuts, are also categorized according to the type of shape. Diamond shapes Oval, Emerald, Pear etc., have a direct impact on other factors that contribute to a diamond’s value. These elements work together to determine a diamond market value. With one factor affecting the quality of others: either by strengthening or potentially weakening its other attributes. The diamond’s shape is one of them. As certain diamond shapes are considered more suitable for certain types of diamond cuts.

Metal type and quality

Diamond quality in fine jewellery is a product of other factors that surround it. In engagement rings, for example, the metal type and quality of the finish will have a direct impact on the quality of the gemstone. Certain diamond cuts combine well with certain engagement ring designs. Whilst certain diamonds, such as those with lower colour grades, are better suited for engagement ring bands that have a specific metal colour (e.g. Rose gold).

Measuring Fancy Coloured Diamonds

Coloured or fancy coloured diamonds are rare breeds of the diamond world. Whilst certain types of coloured diamonds’ value is inversely related to their colour (e.g. brown diamonds, which are sometimes viewed as a worse variety of yellow diamonds). However, this is starting to change as the demand for coloured gemstone picks up. Including demand for certain variants of brown diamonds. The natural value of diamonds is now combined with people’s demand for variety in colour. Thus one of the Cs in the 4Cs is now studied differently. Where the greater presence of colour is no longer viewed negatively. The colour in fancy coloured diamonds is a result of the change in the inner structure of the diamonds. Where the stone’s lattice (atomic structure) carries certain changes that alter its colour tone. With the presence of other elements (like in sapphires) affecting their colour. With some fancy coloured diamonds, like red and pink diamonds, the real source of the stone’s colour remains a mystery. Much work is being done to fully understand the nature of coloured diamonds. Which combined with their rarity (e.g. Argyle diamonds) makes the task more complicated and interesting.