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All About Diamonds: The Complete Buyers Guide

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Buying a diamond can seem like the most daunting task. Diamonds are expensive, rare, and prominent socially and culturally. But it can often feel as if you need to speak a second language to understand what you are buying. An engagement ring may be one of the largest purchases of your life, so it is important to get it right!

emerald cut engagement ring with diamond set shoulders
emerald cut engagement ring with diamond set shoulders

Read on for our comprehensive breakdown of the diamond jargon, what it means, and how important each aspect is to the overall look and value of the stone. Remember that there is no one way to choose a diamond. You may decide that cut is the most important aspect to you, or colour. What is important is that you know what each of these things mean so that you can decide for yourself.


Colour is one of the key attributes of diamonds. The colour grade refers to how colourless a stone is, with the ideal being colourless. This is graded on an alphabetical scale, with D having the least colour and Z having the most. The scale is as follows:

Z-K: Noticeable colour.

J-I: Near colourless; slight colour detectable with human eye.

H-G: Near-colourless; Colour difficult to detect unless compared against better grades.

F-E: Colourless; Very small traces of colour only detectable by a professional gemmologist.

D: Absolutely colourless; The highest colour grade, very rare!

Diamonds ring with channel set baguettes
Diamond ring with channel set baguettes

One of the key features of a diamond is its ability to refract light. Diamonds are cut to allow light to enter the stone, refract around the facets, and reflect back out into the eye of the beholder. This results in what is known as the brilliance of the diamond. The more colourless the stone, the more brilliance it can exhibit.

Some diamonds exhibit a phenomenon called fluorescence. This is caused by different conditions present while the diamond is forming. A diamond certificate will describe fluorescence as 'none', 'faint', 'medium', 'strong' or 'very strong'. Fluorescence should not have an impact on the way the diamond looks, but can cause the diamond to reflect different colours in strong UV light.  The most common colour of fluorescence is blue; less common colours are red, yellow or green fluorescence.

Whether or not fluorescence in a diamond is a positive, negative or irrelevant factor is up for debate in the jewellery industry. The degree to which a diamond is judged as fluorescent is not a grading factor like clarity or colour. It is listed as an 'identifying characteristic' on the diamond certificate. However, a yellow tinged diamond with a blue fluorescence can show up whiter to the naked eye than it would without the blue tinge. This is something to consider if you are trying to save money when purchasing your stone.



The cut of a diamond refers to the overall shape of the stone. Many online and in person retailers will try and sell you a diamond based on it having an excellent cut, but remember that only round brilliant diamonds actually have a measurable cut grade.

For other diamond cuts, it is best to ask to see an image or video of the stone before you purchase it so that you can decide for yourself if you like the proportions of the stone.

There is a set of formulae to determine the cut of a round brilliant diamond. These formulae compare the diameter to the depth of the diamond, and how the proportion of the table compares to the size of the diamond. This helps consumers to determine the cut of a particular diamond. In general, these grades are:

  • Ideal; Reflects nearly all light that enters the diamond. An exquisite and rare cut.
  • Premium; Reflects nearly as much light as the ideal cut, but for a lower price.
  • Very Good; Reflects nearly as much light as the ideal cut, but for a lower price.
  • Good; Reflects most light that enters. Much less expensive than a very good cut.
  • Fair; Still a quality diamond, but a fair cut will not be as brilliant as a good cut.
  • Poor; Diamonds that are generally so deep and narrow or shallow and wide that they lose most of the light out the sides and bottom.


Diamonds form over millions of years in the Earth's crust. As a result of this long, slow formation, many of the stones have what is known as inclusions. These are minerals or gaps in between the layers of carbon.

Most inclusions are not visible to the naked eye. However, sometimes they are a dark colour or particularly large.  If there is anything disrupting the flow of light in the diamond, such as an inclusion, a proportion of the light reflected would be lost, making the inclusions visible.

Inclusions are ranked on a scale of perfection known as clarity. This ranges from FL (No visible characteristics under magnification) to I (Characteristics visible with the naked eye). This grading system does not only measure the inclusions on their size and colour, but assesses the entire stone. This way it can take into account how easy the inclusions would be to hide with prongs or creative setting.

Inclusions in the VVS (Very, Very Slightly Included) to VS (Very Slightly Included) range are only visible under a magnifier. It is only when a diamond is graded 'I' that it is possible to see inclusions with the naked eye.

What's the difference between VVS1 and VVS2 or SI1 and SI2? The numbers represent levels within each grade. The 1s will be cleaner than the 2s.

diamonds clarity

Inclusions appear as different shapes, such as crystals, clouds or feathers. These inclusions often add to the overall character of the diamond. However, as with all things, the closer to perfection you get, the more valuable the item becomes and this is why flawless diamonds command a higher price. It is also worth mentioning that inclusions are weak points in the diamond as they are not made of the hard carbon that the rest of the diamond is formed from. This means that striking an included diamond on the wrong spot could cause it to break.

Engagement ring with open heart setting diamonds
Engagement ring with open heart setting


Carat refers to the diamond's weight. It does not mean size and will not indicate the measurements of a stone. The cut of a diamond can make it appear much larger or smaller than its actual weight. The term carat is actually a derivative of the word carob. Ancient civilisations used carob seeds as a reference for diamond weight. One hundred carob seeds equalled one carat, which is how we came to our modern method of measuring diamonds.

diamonds weight
Carob seeds are surprisingly uniform in weight!

One carat is the equivalent of 200 milligrams. It can also be divided into 100 "points." For example, a 0.75 carat diamond is equivalent to a 75-points or a 3/4 carat diamond. These are all terms that you may come across when shopping for a stone.

So how does the carat affect the price of your stone? You may assume that a 1-carat diamond costs exactly twice the price of a 1/2-carat diamond, but this is not the case. Larger diamonds are much more rare than their smaller siblings. Furthermore, higher carat diamonds can actually appear to be brighter or more brilliant than their lower carat siblings. This is due to the prism effect of light travelling over larger distances.  Because of this, a 1-carat diamond costs much more than twice the amount of a 1/2-carat diamond, even if colour, clarity and cut are the same.

Princess cut diamonds engagement ring with kite setting
Princess cut engagement ring with kite setting


Diamond certification is carried out by one of the highly esteemed gemmological institutes of the world. The most notable of these is the GIA, or the Gemmological Institute of America. Certified diamonds hold more value than non-certified stones, and the certificate can act as a reassurance for the buyer that they have purchased a good quality stone.

The diamond certificate's main purpose is to prove its value. It will confirm the features of the stone such as carat weight, colour, clarity and cut quality. It will also describe other identifying characteristics of the diamond, e.g. fluorescence, polish, symmetry and the specific nature of any inclusions. All these factors together determine the appearance of the stone and how well it sparkles. Each certified diamond will have its own reference number and will be registered with the institute who carried out the grading.

Due to the cost of certification, only the main stone of an engagement ring or any stone larger than 0.25 carats will be certified. It is extremely unusual for melee diamonds or small diamonds in eternity rings to be certified. Certification is priced per stone, so could add a huge cost to the piece of jewellery.

Grain set diamonds full eternity ring
Grain set full eternity ring


Conflict diamonds are those mined in war zones, which are associated with child labour and violence. Changes in policy by governments of the USA, EU and other world organisations has resulted in the Kimberley Process Certification Scheme. This scheme unites administrations, civil societies, and industry in reducing the flow of conflict diamonds - ‘rough diamonds used to finance wars against governments’ - around the world. The UK has subscribed to this scheme and tightened restrictions in the importing of diamonds from potential conflict areas - but it is still up to the consumer to check their diamond is conflict-free.


Diamonds are a unique mineral for many reasons. One of their unique attributes is the ability to attract oils. For this reason, regular cleaning of your stone is essential to maintain its glorious shine.

You can easily clean your diamond with a non-abrasive jewellery cleaner. Be sure to make sure that the cleaner specifies that it is both safe to use on diamonds and the metal your ring is made from. Cleaning your ring once a week will keep dirt from building up and help your prongs or setting remain secure.

Marquise diamonds trilogy engagement ring
Marquise trilogy engagement ring

You should have your diamond ring cleaned by a professional jeweller and inspected once every six months to a year to check that the diamond or diamonds are still secure in their setting. If your ring receives a large impact such as being dropped or knocked on a hard surface, we would also recommend having it inspected. This will help to prevent any stones being lost as a result of the ring being damaged.