Tag Archive | facet

All the “C”s

So whilst it’s lovely to gaze over diamonds and dream, what happens when you want to purchase?  It’s pretty well known that the things to look for in a diamond are the C’s i.e. colour, clarity, carat weight and cut, but what does this mean in reality and is this really all there is to it? 

Diamond grading



Basically the less colour visible the higher the price (except for fancy coloured stones, but again more on coloured diamonds later).  You will mostly come across the GIA grading system which uses a letter system of colour grading. D being the highest grading of colourless, descending towards Z travelling through near colourless, faint yellow, light yellow and so on.  At the very basic level as the colour and grade increases the price of your stone decreases.


Black diamond


Clarity is defined as the degree to which a stone is free from external marks (called blemishes) and internal features (called inclusions). Like with colour the freer the stone is from blemishes and inclusions the more expensive the price tends to be. These factors, like with colour, are given grades; the GIA clarity grades start at F1 “flawless, no blemishes or inclusions” which are very rare and expensive (essentially, “we wish”).  Diamonds are generally found in high street jewellery around lower grades such as SI1 & SI2 which are slightly included, ranging from easy to see under 10x magnification (i.e. using your loupe) and somewhat easy to see with your naked eye. Diamond grades end at I1-I3 (P1 -P3 is used in some countries) which are imperfect, characteristics and flaws which can be seen easily with the naked eye.


D grade diamond ring


The unit of weight used for diamonds is the carat, in most cases the higher the carat weight the higher the price, a carat is a unit of weight equalling 1/5 of a gram. The weight of small diamonds are often expressed in points, with one point equalling 0.01 ct (carat) Diamond jewellery in stores may often have the total diamond weight on display which for example 1ct for a 5 stone ring will not therefore be of an equivalent value as a 1ct single stone in a ring. Also take note if the quantity is expressed in points or carats, as 0.25 points is not equivalent to 0.25 ct which is a quarter of a carat.


This refers to the proportions and finish of the stone, two of the main considerations of cut are:

  • Do you see brilliance all across the stone when you look through the stone face up? You should not see large dark areas.
  • Are you paying for excess weight? is the stone too fat basically when you look at it sideways a poorly cut stone may have a very thick appearance from the side but look much smaller from the top this will also effect the brilliance that stones gives off. Symmetry is also a consideration as this also affects the level of brilliance emitted by the stone.

Cut can be judged by the naked eye and a 10-power magnifier, but it is not as simple as it sounds (naturally!)  Cut should be considered in more detail, looking at the cutting style and quality and the shape of the stone.  The finish is also important as how well the cut is finished can affect sparkle and brilliance.

Whilst cut is very much about personal taste trends affect prices so at the moment round stones tend to cost more than pear, marquise and emerald cuts but this hasn’t always been the case.

Normally square shapes cost less than round as there is less wastage when the stone is being cut from its rough state, and there is usually less demand for squares. However, depending on demand in different areas of the world princess cuts (squares) have occasionally sold for more than rounds.


Heart facet

Anything else…?

Well in short…yes!  (Sorry this is turning into a long post but we promise this is only scratching the surface, hard to do on a diamond!)  Transparency is another factor to consider, the degree to which the stone is clear, hazy or cloudy as again this will alter how the stone reacts to light and therefore how it looks when being worn.

The other thing to take care of when dealing with diamonds is the treatment status i.e. whether the stone has had any external treatment since being mined.  There are a number of techniques and treatments which have been developed to improve the look of white diamonds; some have been deliberate attempts to deceive buyers but with a reputable jeweller you should be able to ask about any treatments of the stone.  An example is the process of using a laser to vaporize black inclusions, this leaves a fine white thread that starts at the surface and travels into the stone.  This treatment is permitted but must be disclosed on any certificate obtained.  Fractures and cracks can be filled with a glasslike substance that is visible only under magnification.  Certain types of yellow-tinted diamonds are put through a high-temperature, high-pressure treatment (HPHT) process to make them colourless. This treatment is permanent and heat treated diamonds can only be identified in a lab.

Depending on what you’re after in a gem treatments are not necessarily something to shy away from, they can reduce the value of a stone but give you the look of a much better quality stone.  One of the things you should beware of though when it comes to treatments (not only in diamonds) is that not all treatments are permanent, the filler we have mentioned above is not a permanent treatment and bad care or handling can loosen the filler or change its colour.