Finding the perfect diamond engagement ring takes a lot of thought, time and effort, not to mention cold, hard cash! There are a seemingly endless list of factors to consider and pitfalls to avoid. Style, shape, setting, stone (or stones), sizes, carats, cuts, clarities, colours… It’s definitely not for the faint-hearted!

So today we show you what to look out for when shopping for rocks. It’s our insider’s guide to diamond engagement rings using the 5C’s of diamond grading. 

Got a budget in mind? Great! You’ll soon have an idea about what size rock/s you can afford. When you start browsing you’ll find jewellers referring to the so-called 4 C’s of diamond grading: carat, colour, clarity and cut. There is however an equally important but less publicised 5th ‘C’ – Certification.

CERTIFICATION

There are numerous independent authorities and private laboratories that assess, grade and certificate diamonds, for a fee of course. The most notable are:

  • GIA – a Gemological Institute of America
  • AGS – American Gemological Society
  • IGI – International Gemological Institute
  • HRD – Diamond High Council
  • CIBJO – International Confederation of Jewellery, Silverware, Diamonds, Pearls, and Stones
  • EGL – European Gemological Laboratory

There are lots of other diamond grading companies too, all easily found online. And some jewellery stores such as Tiffany’s and Boodles even self-certificate their diamonds.

Diamond Certificates are supposed to help reassure the buyer that they are getting a specific quality of stone. However it is essential you understand that there is no uniform diamond grading scale and assessments will vary, so much so that if for instance you took the same diamond to the GIA and the EGL, you would get 2 very different certificates! And unfortunately some certificates are not even worth the paper they are written on.

There is hope though. The GIA is renowned for providing the most accurate, consistent and reliable certificates and as a result GIA certified stones cost significantly more than stones certified by the EGL or any other grading authority. This is demonstrated in the table below which features a selection of loose round stones from Quality Diamonds in London.

diamond certification comparison

As you can see, when keeping all characteristics as similar as possible and the only variable being the certification authority, the table above shows the lowest priced 1 ct stone with a GIA certificate costs £2,545.00 more than the lowest priced 1ct stone from the EGL.

FACT: the EGL are renowned for upgrading stones colours and/or clarities by at least 2 or 3 times more than the GIA.

TIP: For peace of mind, only consider diamonds that are certified by the GIA.

tiffany ring
Tiffany diamond engagement ring

CUT

Diamonds are the most popular gem stones because of their sparkle. The best cut diamonds possess an incredible sparkle and inner fire because their proportions, symmetry and polish enable them to reflect the most amount of light. Whereas a poorly cut diamond looks dull and lifeless because it allows light to pass through it.

The quality of the cut is therefore the most important factor to look for in a GIA certified stone. And of all the C’s the Cut is the only one you should never, ever compromise on. The cut grades are as follows:

  • Excellent
  • Very Good
  • Good
  • Fair
  • Poor

TIP: Do not compromise on Cut – choose an Excellent cut stone. (Or certainly nothing less than a Very Good cut).

CARAT

When purchasing a diamond ring, the first thing most people think about is carat size. It is important to understand that carat (ct) refers to the weight of the diamond and not the size as you might have thought. If you compare a 1 ct round diamond with a 0.5 ct stone, you will notice it does not look twice the size. In fact the difference in diameter is only 1.3mm! Whilst the difference between a 1 and 2 carat stone is just 1.7mm.

FACT: Only 1 in 1,000,000 rough diamonds are big enough to produce a 1 carat cut and finished stone.

1 carat diamonds are the most popular. It’s a nice, round number that guys and girls love. Let’s face it, a 1 carat diamond ring sounds soooo much better than a 0.9 carat ring!

However, what they fail to tell you is that if you want a 1 carat diamond you are likely to sacrifice quality and pay a premium for doing so. This is because most diamond cutters will, if possible, focus on cutting stones to the magical round number rather than cutting to enhance the stone’s natural characteristics. In so doing, the quality of the cutting – and therefore its appearance, brilliance, fire or sparkle – is often reduced.

Need proof? Take a look at the table below. Again the stones were sourced from Quality Diamonds in London.

diamond carat comparison

Keeping all characteristics as similar as possible and the only variable being carat size, the lowest priced 0.9 ct GIA stone costs £4,540.00. Whereas the lowest priced 1 carat GIA stone costs £6,590.00. That’s a whopping 31% increase in cost, for a stone that’s only 10% bigger!

Unfortunately the same applies to stones cut to other magic round numbers – 0.5, 1.5, 2, 2.5 and so on.

TIP: Stones just under 0.5, 1, 1.5, 2, 2.5 or 3 carat offer great value for money

Of course, you don’t want to give your wife-to-be an engagement ring that’s only 0.9 carats! You want to hit the magic mark! Don’t worry, you still can… by setting some smaller diamonds in the shoulders or flanking or encircling the centre stone.

COLOUR

In case you didn’t know, diamonds come in a variety of colours and shades including pinks, blues, greens, yellows, oranges, reds, purples and browns. However coloured diamonds are not the focus of our attention here. We are concentrating on white diamonds.

White diamonds are graded on a scale from clear and colourless through to light yellow. Colourless stones naturally command the highest prices in the market place.

  • Colourless: D, E, F
  • Near Colourless: G, H, I, J
  • Faint Yellow: K, L, M
  • Very Light Yellow: N, O, P, Q, R
  • Light Yellow: S. T, U, V, W, X, Y, Z

Colourless D and E graded diamonds are practically ice-white, very rare and expensive.

F colour diamonds possess a hint of colour that’s often only perceivable by a trained diamond grader when viewing diamonds side by side. And to the untrained eye it’s very difficult to tell the difference between a D, E & F coloured stone.

Diamonds graded near colourless G, H, I or J appear colourless when viewed face up. It is only when you look at them face down and against a white background that you will notice they possess a hint of colour.

diamond colour comparison, D-J
Comparing colour grades

Moreover, when a near colourless diamond is set in an engagement ring, it will be extremely difficult to tell whether it’s a colourless or near colourless stone! Therefore it’s a sensible idea to opt for a near colourless diamond since they offer the best value for money without noticeably compromising on quality.

diamond colour comparison

Keeping all characteristics as similar as possible and the only variable being colour, the lowest priced 1ct D colour stone from Quality Diamonds costs £7,545.00. Whereas the lowest priced 1 carat I colour stone costs just £5,100.00. It’s a saving of 32%!

TIP: Near colourless H/I colour stones represent excellent value for money and won’t compromise on appearance.

CLARITY

The clarity of a diamond is an assessment of the stone’s blemishes. The more external blemishes or internal inclusions it has, the lower the clarity grading. Stones are graded accordingly:

  • FL, Flawless: No inclusions or blemishes visible to a skilled stone grader using 10x magnification.
  • IF, Internally Flawless: No inclusions and only blemishes visible to a skilled stone grader under 10x magnification. Less than 2% of all the diamonds in the world are FL & IF clarity.
  • VVS1/VVS2, Very, Very Small Inclusions 1/2: Inclusions are difficult for a skilled grader to see under 10X magnification. Approximately 7% of all diamonds are VVS clarity.
  • VS1/VS2, Very Small Inclusions 1/2: Some minor inclusions, some hard and some easy for a skilled grader to see under 10x magnification. Approximately 14% of diamonds are graded VS.
  • SI1/SI2, Small Inclusions 1/2: Inclusions are noticeable to a skilled grader under 10x magnification. 25% of all diamonds are SI clarity.
  • I1/I2, Inclusions 1/2: Inclusions are obvious under 10x magnification affecting transparency and brilliance. 52% of diamonds are I clarity.

TIP: VS2 diamonds offer the best value for money. These ‘eye clean’ stones have no inclusions visible to the naked eye.

FLUORESCENCE

Having covered the 4/5 C’s of diamonds there is one other equally important factor to bear in mind. Unfortunately, it’s not a C… It’s an F!

Fluorescence refers to an often bluish hue that many diamonds possess and display when exposed to UV light. The amount varies from stone to stone and is graded from None to Very Strong. It can affect the appearance of a diamond for better or worse.

If you have your heart set on a Colourless/Near Colourless diamond in the D-G range, any level of Fluorescence can negatively impact on the appearance of the stone. No fluorescence is ideal and Faint fluorescence should be fine but you need to inspect the stone. Reject any with a Medium or higher rating.

However Near Colourless diamonds in the H-J range as well as some K colour stones will often benefit from Medium fluorescence, which can make them appear a shade whiter!

Whilst stones with Strong or Very Strong fluorescence may appear hazy or milky.

TIP: Opt for Faint or No Fluorescence in D-G stones & Medium Fluorescence in H-J stones

CONCLUSION

  1. To ensure you get the highest possible quality and value for money, choose a diamond Certified by the GIA.
  2. Always opt for an Excellent Cut
  3. VS1 or VS2 Clarity represents exceptional value for money
  4. And if you want a specific number of Carats in the ring, consider a slightly smaller centre stone and make up the rest of the carat weight with some small diamonds in the shoulders of the ring or encircling the centre stone.