The 4Cs of Diamonds


4 Cs Overview


For many people, buying a diamond for the first time can be an overwhelming experience. Faced with such variety of choice and wildly differing prices, it's understandably confusing if you aren't familiar with a diamond's quality characteristics. In truth, there are many features discussed when buying a diamond. But which are of greatest importance?  How can we, as consumers, ascertain the value of a diamond? 


Quite simply, by understanding the 4 Cs of diamonds. The 4 Cs – colour, clarity, carat and cut – are the key characteristics by which all modern diamonds are identified, evaluated and priced.  See below video for an overview of 4C’s as explained by the Gemological Institute of America (GIA).  You’ll also learn about how 4C’s are graded.


GIA 4Cs Video




1. Colour:


In most people’s mind, diamonds should appear colourless, however, most diamonds actually comprise subtle natural hues of brown and yellow. These colours are influenced by chemical impurities caused when diamond ore is heated by magma. Very few mined diamonds are ever completely colourless. 


Colour is one of the chief characteristics assessed when a diamond is valued. To purists and gemmologists, the worth of a diamond increases the more colourless it appears. The internationally recognised GIA established a comprehensive colour grading scale in the 1960's based on a rough guide previously used by the London Diamond Syndicate. Since the colour nuances between diamonds are extremely subtle, grading is achieved by inspecting the stones under specific white fluorescent lamps that give off light equivalent to natural daylight. A set of GIA approved master stones is also used for precise colour reference.

The grading scale above encompasses all subtle nuances in colour ranging from completely colourless (D), through to light yellow (Z). Any diamond with a stronger depth of colour beyond 'Z' is usually referred to as a “fancy” diamond.   See below the color differences between each grade


At England Diamond, we inspect each and every diamond for colourless value. For quality assurance reason, we only retail diamonds with a colourless value of D to L, and will recommend the right colour that suits your budget and needs.



2. Clarity


Due to their origin and composition, nearly all diamonds bear traces of other minerals and blemishes affecting either their outer or inner aesthetic. Exterior markings, such as scratches, are known as “blemishes”, whereas features such as internal fractures or crystals are known as “inclusions.” Flawless diamonds (those without inclusions and blemishes) are exceptionally hard to find, and naturally carry a hefty price tag befitting of their rarity. 

Diamond “clarity” is the measure of inclusions and blemishes affecting the inner and outer aesthetic of a diamond.  Most blemishes are invisible to the human eye, yet can often be identified with the aid of a 10x jeweller's magnifying loupe.  Although invisible to the human eye, these imperfections can affect the amount of light reflected and refracted by the diamond – thus reducing its brilliance, fire and scintillaion. The fewer inclusions and blemishes identified, the purer and more valuable the diamond. 

Clarity is determined under 10x magnification, measured in accordance with the globally recognised 11-grade GIA Clarity Scale. 

The  below table depicts the GIA clarity scale, followed by an overview of each grade according to the prominence of inclusions:




‧Flawless (FL) - No inclusions/ blemishes are visible to an expert gemologist under 10x magnification


‧Internally Flawless (IF) - No inclusions, and only very subtle surface blemishes are visible to an expert grader under 10x magnification


‧Very, Very Slightly Included (VVS1 and VVS2) - Inclusions are present, yet extremely or very difficult for an expert to pinpoint under 10x magnification


‧Very Slightly Included (VS1 and VS2) – Minor inclusions are present, and somewhat difficult (VS1) or somewhat easy (VS2) to be seen under 10x magnification by an expert grader.


‧Slightly Included (SI1 and SI2) - Inclusions are present and obvious to an expert grader using 10x magnification.  They are sometimes (SI1) or often visible (SI2) to the naked eyes even without the help of a magnifier.


‧Included (I1, I2, and I3) - Inclusions are apparent under 10x magnification, and at this stage, usually affect both the clarity and brilliance of a diamond.  Further, they are mostly visible to the naked eyes, and sometimes cause durability issue to the diamond.


See below interactive scale from the GIA



3. Cut

The quality of a diamond's “cut” is first determined by assessing three key “aesthetic”attributes: brilliance (how much light is reflected by the diamond), fire (the measure of light dispersed into colours) and scintillation (the sparkle, the relative size, arrangement, and contrast of bright and dark areas). Experts consider these attributes combined to be of the utmost importance when valuing a stone, since a poorly cut diamond with ideal colour and clarity will not give off an acceptable fire or brilliance

Next, a physical measurement of the diamond would quantify and re-confirm the performance of a diamond’s cut.  Proportions are calculated by assessing table size, crown angle, depth of the pavilion, girdle thickness, and culet size, etc.  In particular, if the pavilion depth is too shallow or too deep, light will be refracted through the sides and base of the stone, causing it too appear dull. 


                  Excellent Cut                                                   Very Good Cut



               Good Cut                                Fair Cut                               Poor Cut


Source: Courtesy of GIA 

4. Carat

“Big girls need big diamonds” was an inspirational quote coined by Brit-American actress Elizabeth Taylor. But she wasn't only referring to the aesthetic proportions of her favourite gemstones.

Nearly all gemstones are weighed in metric carats; one carat being equivalent to 0.2 grams. The term derives from the use of “carob” seeds, which, due to their uniform weight, were commonly used to balance merchant scales.

Carat weight can also be interpreted in points, as illustrated below:


1 carat       = 100 points
3/4 carat    = 75 points
1/2 carat    = 50 points
1/4 carat    = 25 points
Melee         = Less than 15 points


Note: If a retailer refers to carat weight in points, remember that the price of one-carat diamond will far exceed that of one weighing 95 points. 

By learning the carat weight of a round brilliant diamond, you can usually determine the approximate size of a diamond.  The table below gives an estimation of a diamond’s size vs. its carat weights:

So how do you choose between the size of a diamond and the quality (i.e. the other 3C’s) of a diamond? What is the optimal choice?  Please read our article “Choosing the perfect 4C’s combination” to find the answer.

With the knowledge of 4Cs, you are now equipped with the ability to differentiate between diamonds of poor and excellent quality.  Yet, beyond the 4Cs, many consumers are looking deep into the finish and fluorescence of a diamond.  If you’re interested to learn more, read on.