Diamonds have always been associated with love and romance. The hypnotising sparkle speaks volumes. A diamond is the stone traditionally chosen to celebrate a momentous occasion: an engagement, wedding, anniversary, birthday or just a treat for yourself.

Buying a diamond doesn’t have to be overwhelming – it should be exciting! To make an informed decision and pick the perfect diamond, consider the four Cs: Carat weight, Clarity, Colour and Cut. Considered together, these factors determine the overall beauty, quality and price of a diamond.

Carat weight

In the jewellery world there are ‘karats’, which refer to gold weight; and ‘carats’ (ct), which describe diamond weight. A carat is made up of 100 points; a half-carat diamond therefore weighs 50 points.

When set jewellery has one or more diamond, you’ll often hear the term ‘total diamond weight’. A ring with a 0.50 ct centre stone and two 0.25 ct side stones will have a total diamond weight of one carat.


Clarity refers to a diamond’s degree of freedom from:

Diamonds form under tremendous heat and pressure over thousands of years, so it’s almost inevitable that they’ll have some form of inclusion or blemish. Clarity characteristics are what make a diamond unique – two diamonds possessing the same ones are as likely as two people having the same fingerprint.

Clarity is measured according to clarity grades. These are based on the Gemological Institute of America (GIA) scale, which ranges from flawless (FL) to included (I). Apart from I grade stones, where the inclusions can be seen with the naked eye, most clarity grades are determined under 10x magnification.

Here’s a breakdown of what the clarity grade codes mean:

Better a diamond with a flaw, than a pebble without – Confucius


Colourless diamonds are the traditional white stones usually seen in jewellery. Pink, blue and other coloured diamonds are referred to as 'fancy coloured' diamonds.

The GIA colour grading system starts at D, which indicates totally colourless stones, and ends at Z, the most coloured. Generally stones above the J colour are colourless to the untrained, naked eye. This is how you might describe colour grades along the scale:


The cut of a diamond refers to two different things: the actual shape (round, heart, oval etc) and the make or proportions of the stone.


The classic round brilliant shape is the most popular. Shapes other than round brilliants are called ‘fancy shapes’, such as those below.

Round brilliant

A round cut with lots of facets for maximum sparkle, the round brilliant is our most popular shape. See all of our round brilliant cut engagement rings or wedding rings.


The princess is a square cut with a modern clean look. Extra facets on the corner give it a good sparkle. See all of our princess cut engagement rings or wedding rings.


A rectangular step cut with less brilliance – still a classy, elegant look. See all of our emerald cut engagement rings.


Also called a 'teardrop' or 'pendeloque', pear-shaped diamonds are a hybrid of round and marquise shapes. They are often used as side stones in engagement rings to enhance the centre stone of a more popular cut. See all of our pear cut engagement rings.


When the shape is right, this cut can make a stone look bigger. It's a good shape to make fingers look long and elegant. See all of our marquise cut engagement rings.


A triangle-shaped stone, often used to flank the centre stone in a three-stone ring.


Baguette cut diamonds can either be straight cut or tapered at the ends. These stones are cut from a variation of the emerald cut. Baguette cut diamonds are often used as shoulder diamonds in wedding bands and engagement rings. See all of our baguette cut engagement rings.


The inspiration for the emerald cut, the Asscher was created in the late 1890s. It is step cut – when you look at it you can see the steps descending into the stone.


The amount of light reflected by a diamond depends on its proportions. If you want a diamond that has a lot of sparkle then you have to make sure the stone proportions are good. A pavilion with proportions that are either too deep or too shallow allows light to leak out the bottom of the stone, and reduce the amount of light that strikes your eye.

Proportions determine a diamond’s ‘fire’ (rainbow colours) and ‘brilliance’ (those flashes of white light we like so much). The better the cut (the proportions and symmetry of the stone), the more sparkle you’ll get.