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How to choose for the perfect diamond for your engagement ring…

Recently I’ve been working a lot on diamond ring commissions. One of the first questions our customers ask is, “which of the 4 C’s is most important?” So, I thought I would give you a whistle stop tour through the diamond purchase and consideration process…


Firstly, what actually are the 4 C’s? The 4 C’s are as follows:

  1. Cut
  2. Clarity
  3. Colour
  4. Carat weight.

I would describe each one as having a movable slider, which allow for variations that can be played around with to make sure that you get the best and most stunning diamond for your budget. 

Let’s look at cut first. This is my number one thing to look out for as it has the most effect on how a diamond sparkles and catches the light. A precisely cut, well portioned diamond is down to the skill of the cutter, which is then evaluated by the diamond grader. The five different GIA (Gemstone Institution of America) levels of cut are as follow:


  1. EX - Excellent
  2. VG - Very Good
  3. G - Good
  4. F - Fair
  5. P - Poor


The grading of the diamond has nothing to do with inclusions at this stage. A stone with lots of inclusions can still be classed as Excellent. (NB this scale only relates to round brilliant-cut diamonds. Fancy cut diamonds (the term “fancy cut” in this case refers to diamonds that have different cuts, like emerald cut for example) have their own scale and rating system.

You want to choose a stone which has the best cut available as this is the number one thing that people notice about diamonds!

The second most important ‘C’ is Clarity – this is where inclusions come in. The term ‘Clarity’ refers to ‘inclusions’ and ’blemishes’ that might be visible in the stone. As diamonds are formed under extreme pressure and heat, no diamond is perfect. The grading system is designed to indicate how and what type of inclusions are present in the stone, and how this affects the way they refract light, i.e. sparkle.

There are lots of different types of inclusions; these are the main ones you will come across;


  • Bearding - this occurs during the diamond cut and is small hair-like lines that go into the surface of the gemstone. 
  • Cavity - a large opening in the gem's surface.
  • Feather - a small fracture internally within the stone, this can be invisible from certain angles and resemble a feather in others. 
  • Cloud - refers to a cluster of crystals near to each other. If a cloud is prominent it can affect the diamond's clarity and appearance. 
  • Crystal - when a mineral crystal is within the diamond. As these crystals can contrast in colour with the stone, this level of diamond clarity is often undesirable. 
  • Chip - this is a small opening on the surface of the gem and is manmade by accidental knocks. 
  • Knot - a knot is a clear crystal that is present on the surface of a polished diamond.
  • Graining - this too refers to crystals within the gemstone, in this case they have a hazy appearance and can be seen as lines.


Types of diamond blemishes:

  • Polish Line - these occur in the polishing of the diamond - this is how the diamond shape happens. These will only be present on one facet and do not extend to the next.
  • Abrasion - these are a group of small nicks on the surface that can cause the edges to have a white appearance.
  • Natural - this is where an edge has been left as the original surface, e.g. the rough diamond.
  • Nick - this is a small indent on a facet junction.
  • Scratch - a thin line across the diamond's surface.


The GIA grading system for clarity goes as follows:


  • FL - These diamonds are flawless
  • IF - Are internally flawless
  • VVS1 & VVS2 - Very, very slightly included- grade 1 and grade 2
  • VS1 & VS2 - Very Slightly included - grade 1 and grade 2
  • SI1 & SI2 - Slight included - grade 1 and grade 2
  • I1, I2, & I3 – Imperfect- grade 1, grade 2 and grade 3


Here we would recommend choosing a diamond which is ‘eye-clean’ meaning you can’t see at a glance any inclusions that might be present.

When you buy a certified diamond, which we always recommend doing, your diamond will come with a certificate showing exactly what the inclusions and blemishes are and where they are on the stone. A cleverly designed ring can sometimes hide big, off-centre inclusions, so it’s always worth discussing this with your jeweller before you make a decision.

The third “C” is Colour. A lot of this is down to personal preference – you don’t always have to go for the classic clear diamond. There are some really stunning options if you have a lower budget in mind, like light yellow diamonds. This is where I would help you to find the best option that suits you and what you want to create.


The actual colour scale runs from ‘D’ which is colourless to ‘Z’ which has a light yellow tint:


  • D-F - Colourless
  • G-J  - Near colourless
  • K-M – Slightly tinted
  • N-Z – Lightly coloured


All the diamonds from D to J will be very difficult to distinguish in terms of colour to the naked eye, unless compared with the most colourless stone (from the ‘D’ category). It’s all about striking the balance between beauty and affordability, which is completely subjective for everyone.

The last of the 4 C’s is Carat. Personally, I think this is the least important of the C’s. People tend to get hung-up on the size of the stone, not realising that it doesn’t always mean that it’s the best quality!

What it boils down to is weight. A carat is divided into 100 milligrams which allows for a very precise measurement. Diamonds with higher carats are more expensive as they are rarer to find, but prices vary massively depending on the other 3 variables. This is why size, whilst important, should be the final thing to consider and something to compromise on, if necessary.

Diameters per carat go as follows:


  • 50ct diamond = 5mm diameter
  • .75ct diamond = 5.7mm diameter
  • 1 ct diamond = 6.5mm diameter
  • 5ct diamond = 7.3mm diameter
  • 2ct diamond = 8mm diameter
  • 3ct diamond = 9.1mm diameter


If you have any questions regarding diamond selection, engagement rings or bespoke pieces, then I’m always happy to help.

Creating the perfect ring for somebody can be a daunting process, but I’m here to help you navigate through from concept to completion, so you can create something truly unique that will last forever.

Hopefully this article answers some of the big engagement ring questions you were worrying about. If you have any further questions then please do feel free to email us; and we will do our best to answer them. More information can be found about our Bespoke by Antonia Guise here.