What are the "4 C's"?

An Overview of the "4 C's"

In 1953 The GIA created the first globally accepted standard "the 4Cs" to which a diamond could be assessed based on four characteristics of a diamond, namely its Colour, Clarity, Cut and Carat.

Diamond Colour

A structurally perfect and chemically pure diamond has no hue and therefore has a higher value. The GIA D-Z diamond Color grading system measures the degree of colourlessness under controlled lighting, with D being colourless, all the way down to yellow and brown stones.

diamond colour chart d-z

Many Color distinctions are so subtle and invisible to the untrained eye, and are assessed under magnification. However these distinctions do impacted the perceived desirability and price of a diamond.

Diamond Clarity

The process of diamond exposure to deep pressure and heat can result in formation of internal characteristics called ‘inclusions’ and external characteristics called ‘blemishes’.

Assessing 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.

Diamond Cut

A diamond’s cut is paramount to the stones final beauty and therefore value. The cut grade is determined by how well a diamond’s facets interact with light in terms transmission, reflection and refraction. It is without a doubt the most complex attribute of a cut diamond to analyse.

Both workmanship and precise artistry are required to fashion a stone so its proportions, symmetry and polish deliver the characteristic optical properties of a high quality Diamond.

To determine the cut grade of the standard round brilliant diamond – the certifying body (IGI/GIA) calculates the angles and proportions of the precious stone vs ideal reference values based upon work by Marcel Tolkowsky in the early 20th century.  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


Diamonds and Carats

A diamond carat weight measures how much a diamond weighs. A metric “carat” is defined as 200 milligrams. Each carat is subdivided into 100 ‘points.’ This allows very precise measurements to the hundredth decimal place.

Whilst a Diamonds Carat weight will impact its overall dimensions and size, its shape will also be a critical factor. The relationship between weight, shape and dimensions of a given Diamond can be seen below:

Diamond Size Chart table Measurements Carat Weight Dimensions

A jeweller may describe the weight of a diamond below one carat by its ‘points’ alone. For instance, the jeweller 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.’

Due to both rarity and desirability, diamond price increases with diamond carat weight.



How To Use the 4C's When Buying a Diamond

  • Ideally you should have an idea of budget or budget range for your purchase, whether its an Engagement Ring, Push Present or a pair of earrings. Once this is established, you can then begin to narrow your search to get the most sparkle and impact for your buck.
  • Of the 4C's it is widely considered that the Cut is the most important factor when selecting a Diamond, as this will greatly impact the manner in which light is reflected, and this can be noticeable from even across a room! We would strongly advise prioritising cut, ideally going for excellent or very good.
  • The colour of a Diamond is only noticeable from a few feet away, and when moving from colourless to near colourless the difference is even less discernible. Moving from a D colour to an E can greatly reduce the cost of an otherwise equivalent Diamond.
  • Inclusions by their very definition are described under 10x magnification, so will only be visible from close up, in fact only inches away. SI1 and even SI2 can look exceptional to the naked eye, whilst maximising your budget.
  • The Carat weight is another important practical consideration, and its important to note this described the WEIGHT of a Diamond and NOT its size. The appearance of how large a Diamond appears is down to many factors including its shape, ring setting, and anatomy (hand size, finger size and dimensions etc).  Prices also jump massively at half and whole carat points ("magic sizes") so buying just shy of these will also provide much better value. For example the visual difference between an equivalent 0.9ct and 1ct Diamond will be very little, however all other things being equal, the 0.9ct will be significantly better value.
  • Shape; Round Brilliant Diamonds have their cut specifications set by the GIA, and are typically more expensive due to this factor. Fancies are any other shape for example Princess, Asscher, Heart, Oval or Pear shaped stones. With all things being equal, the per carat price will vary between shapes, with some Fancies providing exceptional value. Many Fancies will also appear larger than a Round Brilliant of an equivalent Carat weight.


chart of diamond price by shape comparison

How Does Diamond Shape Affect Price?

The above table compares prices of different shaped Diamonds with the same 4C specifications. (Please note prices constantly update, the figures will not be accurate vs live pricing). Courtesy of gemsociety.org

 Should you have any further questions or specific queries feel free to Contact Us


1. https://www.igi.org/diamond-reports/en

2. https://www.gia.edu/UK-EN/gem-lab-service/diamond-grading

3. https://www.gemsociety.org/article/diamond-shapes-price-size/