Diamond Jewellery Guide

Girl Wearing Diamond Earrings

The ultimate guide to diamond jewellery

Born deep below the Earth’s crust a billion years ago or more, diamonds are one of our most enduring symbols of luxury, elegance and grace. Their dazzling sparkle has captivated our imaginations for centuries and they are unquestionably the most highly desired stone in jewellery making. 

The conditions that create diamonds are uncommon and take place miles underground, out of sight. Only a small portion of all the diamonds in existence will ever be close enough to the surface to be collected, making them one of the most rare and precious stones of all.

The unique beauty of a diamond lies in its structure. The stones are made completely from carbon which has been tempered by the extreme heat and pressure within the Earth’s mantle, resulting in a crystal structure which is perfectly uniform. 

It is this unique structure which gives diamonds their astonishing clarity and unbeatable sparkle as it allows light to pass through the stone without being diffused by imperfect crystal alignment. As each carbon atom is as tightly packed as possible within a diamond, they are incredibly hard and dense.

Diamonds are one of the absolute hardest natural materials, being a 10 out of 10 on the Mohs scale of hardness. It’s well known that diamonds are so tough that the only thing that can scratch them is another diamond. 

Girl Wearing Diamond Necklace

How are diamonds graded? 

Much like the human fingerprint, every single diamond is unique. Subtle variations in the colour, cut, clarity, and carat weight are used to distinguish between them and assign them a grade. While white diamonds are possibly the most popular, they come in a range of naturally occurring colours including black, pink, blue, green, red and yellow. 

Every diamond is valuable, but their specific value is directly related to the characteristics mentioned above. Highly graded diamonds are not only astonishingly beautiful, they also make the wearer feel opulent, confident and powerful. The appeal of diamonds is completely unique, and nothing comes close to replicating their natural glitter. 

Assessing the quality of diamonds using the four Cs

When a diamond is collected it undergoes an in-depth grading process to determine its value, and this draws on the four Cs of diamond grading: cut, clarity, colour and carat weight. The more highly a diamond scores, the higher its value will be. The most highly graded diamonds can command multiple millions of pounds in the rare event they are sold. 

Diamond cut

The cut of a diamond will dictate the way its facets interact with the light. The quality of a diamond is largely influenced by its cut as a poorly cut diamond will never look as brilliant as it should, even if its clarity and colour are excellent. When a diamond cut is just right, its geometry will interplay with the light so that its surface sparkles enchantingly. 

A skillful diamond jeweller understands this and makes precise cuts so that light entering the diamond is reflected back up to its upper surface facet rather than escaping through the sides of the stone. Controlling the movement of light through a gem makes the difference between a high quality gem that looks glamorous and one that falls short on sparkle. 

The quality of a cut is determined by the size of the facets, depths of the angles and its overall symmetry. If the angles are too deep or too shallow the stone will look dull. A precision cut allows experienced diamond cutters - known as lapidarists - to ensure that every diamond they cut has perfectly aligned geometry and absolute symmetry. 

 The highest possible diamond cut grading is categorised as ‘excellent’, and only stones which have been cut with high levels of precision, perfect alignment and symmetry, and perfectly placed facets can achieve this coveted status. The next highest level of cut quality is ‘very good’, which is followed by ‘good’ diamond cuts, ‘fair’ diamond cuts, and ‘poor’ cuts. To know more about diamond cuts, check our guide to diamond cuts.

Diamond clarity

When considering the clarity of a diamond the most important factor is the purity of the stone. As diamonds are a natural stone they can often have small internal flaws and inclusions. Usually these are too small to be noticeable while you are wearing your jewellery and may only be visible when you look at the stone very closely or use magnification. 

If a diamond has no visible internal flaws and no imperfections to the external surface under 10x magnification it is considered flawless. These diamonds carry some of the heftiest price tags in jewellery making and are highly sought after, they are also incredibly rare with only 0.5% to 1% of all diamonds achieving a flawless certification. Flawless diamonds are graded as ‘FL’.

Diamonds which are flawless internally but have some exterior blemishes are registered as IF, standing for ‘internally flawless’. These diamonds have no inclusions inside, and are perfect aside from very minor surface blemishes which are difficult or impossible to see with the naked eye. In most cases they are completely indistinguishable from FL diamonds and only skilled gemologists will be able to tell the difference. As such they are just as rare and often as pricey as flawless diamonds.

Further down the diamond grading scale are very very slightly included diamonds, which are listed as VVS1 or VVS2 depending on the unique makeup of the stone. These beautiful gems have very tiny amounts of inclusions which are invisible to the naked eye and must be detected under magnification. Very slightly included diamonds (VS1 or VS2) have more inclusions than VVS stones, though these imperfections also can’t be seen by the naked eye. Around 40% of all diamonds sold fall into the VS1 or VS2 category, making them one of the most popular choices for diamond jewellery. VS1 and VS2 diamonds hit the sweet spot between stunning natural beauty and affordability.

The next diamond grade is ‘slightly included’ and this is abbreviated to SI. You can get SI1 and SI2 diamonds, with SI1 being the higher quality of the two. These diamonds, while being beautiful, do have some more noticeable inclusions than more highly graded diamonds and so are much more affordable.

Diamond grades below this are considered ‘included’ which means they contain visible imperfections. This class is split into three: I1, I2, and I3. The inclusions within these diamonds are significant enough to affect the way light enters the stone and is reflected, which can make a flaw even more noticeable. As such, these diamonds tend not to be used for premium jewellery as they will never have the sparkle and shine of high quality natural stones.

Diamond colour

Diamond colour refers to the degree of tinting within a white diamond. The vast majority of natural white diamonds will have some level of yellow tinting within them, and diamonds which are closer to pure white are rare and highly sought after.

The colour rating of a white diamond is given alphabetically, D to Z. Diamonds rated D, E, or F are rare colourless diamonds. G, H, I, and J diamonds are next and are considered near colourless. Diamonds rated as K to Z carry a progressively stronger yellow tint.

Not all diamonds fit along this pure white to intense yellow scale, and in fact most have a somewhat brown hue. Brown diamonds are becoming more popular for fine jewellery, though it is more common to see them used industrially rather than decoratively. Diamonds can also be black, pink, red, orange, green, grey, or blue among other colours. 

It all depends on the chemical compounds that were present when the diamond was formed in the Earth’s mantle. Diamond colours also exist on a scale, so any coloured diamonds can be classified as faint, very light, light, fancy light, fancy, fancy intense, or fancy vivid depending on the depth of their colour. 

Diamond carat weight

Diamond weight is measured in carats, not to be confused with karats which measure the purity of gold, and it is not a measure of the size as some believe. One carat is equivalent to 0.2g and diamonds of varying carat weights will look different depending on their shape.

The depth of a diamond cut affects the size, so if two diamonds were of equal carat weight but one was cut more deeply than the other, the deeply cut diamond would appear smaller. Carat weight alone is not enough to determine a stone’s value, and it must be taken into consideration alongside the other factors making up the four Cs of diamond grading.

For more information about fine jewellery and other of materials, check out our jewellery guides.