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Although all gemstones are graded to an extent, diamonds always have to be a bit special because of their significant value, and perceived rarity.

If you know nothing about diamonds you still are likely to have heard of the the "4 Cs",. These are the four criteria by which we grade a diamond: colour, clarity, carat and cut.

As with anything remotely technical the language can be confusing, so here is our no-nonsense guide to diamond grading, where we will explain the 4 C's (as well as two others: Cost and Certificate) and then give you some of our inside tips and tricks we picked up working in the diamond trade. 


Diamond shapes 2.jpg

Why do we start at D?

Before the official, GIA, diamond grading system (above) was introduced, grading diamonds was very ad hoc. It was common for a diamond dealer to refer to a diamonds colour as AA+ or B etc. (a system still used with gemstones today). GIA wanted no confusion between their new colour system and the unofficial grades given by tradesmen and so began at D. 

Can I tell the difference?

Diamond colour grading is a very precise art. In order to grade in lab conditions you need a white 'colour card', white light and a very well trained eye. 

The colour differences we are looking for are minute and it takes years to be able to build up the mastery needed to grade accurately 100% of the time. Often when graders begin they use a set of 'master' stones, which are Cubic Zirconias, coloured to represent each diamond colour grade above. 

For this reason, to the untrained eye, it can be very difficult to see the difference between two colours. One of our favourite tests is to put three diamonds, graded D, E and F, in one colour card and ask our client to tell them apart. No one has ever got it right. 

Where you will start to see a colour difference is between the different groups of colours i.e. a D and a G colour, or a G and an I.

Does the setting matter?

In short, yes. 

If you have a 'nearly colourless' stone or below, the tint of colour in the diamond will look a lot more stark next to a white metal setting. This is because the silver accentuates the warmer colour of the stone.

On the other hand, if you set this tinted stone in a yellow or rose gold setting, then the stone will appear much whiter next to the coloured metal.

It is because of this that we recommend only setting G+ diamonds in white metal settings (with the exception of fancy coloured stones) and all others in yellow or rose gold. 


If you have your heart set on a fancy coloured diamond but want to keep costs down, select a lower colour 'white' diamond (N or below) and set the stone in a rubover setting with a solid gold plate under the stone. The gold will shine and reflect through the stone and make it appear much more yellow than it really is. 


Diamond shapes 1.jpg

What are inclusions?

As diamonds look like perfect, sparkling, crystals on your hand, it is easy to forget that they are in fact, natural.

Because diamonds grow deep in the mantel of our earth over millions of years, they are prone to picking up some added extras along the way. Think of it like our skin as we grow, collecting moles, scars and bruises. 

Inclusions in diamonds can be a variety of things, from Carbon to whole little baby diamonds trapped inside a larger one.

What clarity should I go for? Those black marks look scary.

Although the drawings above look a little scary, they are actually illustrating microscopic blemishes on the inside of a diamond.


You should not be able to see any inclusions with your naked eye of a diamond graded SI2 or above. 

However, whilst your eye won't be able to tell the difference between a flawless stone and a slightly included one, we assure you your wallet will. 

Do inclusions affect the durability of my diamond?

Inclusions are mainly microscopic blemishes in the stone, unable to be seen with the naked eye and won't affect the durability of the stone.

The only inclusions that will affect your stones longevity are the diamonds graded "Included", but A Bespoke Life does not deal with the stones (unless requested.)

Clarity is the 'C' that affects the price of a diamond the most, aside from Carat. The difference in price between a 1ct D IF and a 1ct D SI2 is approximately £10,000. 

So unless clarity is exceedingly important to you, we recommend putting your money where you can see it and going for a larger carat weight and better colour!



Diamond shapes 3.jpg

The standard mm size for a 1ct diamond in each shape

What is carat?

Carat is the unit of measure we use to weigh diamonds and gemstones. One carat is the equivalent of 0.2g. 

Because some gemstones are more dense than others one carat of diamond, for example, will look very different in size to a carat of moonstone. 

What is the relationship between carat and shape?

To cut the different shapes of diamond a diamond cutter uses different proportions; this means two stones of the same carat weight, but with different cuts, can look very different in size.

Above is a chart is a comparison, which shows various diamond shapes and the standard mm size they are at 1 carat.

As you can see, the measurement of a marquise cut stone is almost double that of an asscher cut stone of the same weight. So if you want to have the look of a bigger stone, but for the same price, try exploring different shaped stones. 

If you would like to know more about diamond shapes click the link to our other info page.


Carat weight is the factor that affects the price of your diamond the most. 


When costing diamonds we work to certain bench mark numbers: 0.25ct, 0.50ct, 0.75ct, 0.90ct, 1ct, and so on. If you want to get more for your money then we suggest purchasing stones that fall just below these benchmarks, such as a 0.97ct. 

A 0.97ct stone will look almost identical in size to a 1ct stone, but won't carry the same price tag! 

However, these carat weights really are magic stones to find. A cutter never cuts a diamond wanting it to be a 0.97ct, they cut for a 1ct and have a bad day. So if we find them, we snap them up!


(polish & symmetry)


Anatomy of a diamond

What is cut?

All diamond shapes are graded on the quality of their polish and symmetry. However, only the round brilliant is graded on a third factor: cut. 

Diamond cut refers to exacting proportions of a diamond, for example, the table being between 53-57.5% of the stone, and the pavilion angle 40.5-41.5 degrees. 

The differences are minute and grading a diamond's cut takes meticulous measurements and calculations (or some fancy machines with lasers.)

Due to this, it is only certified diamonds that will come with a cut grade. Uncertified stones will only be graded on colour, clarity and carat.

How is cut graded?

There are five cut grades that can be awarded to a round brilliant cut stone: Excellent, Very Good, Good, Fair and Poor. 

What are the proportions of an excellent cut?

Total depth: 59.9-63%

Table diameter: 53- 57.5%

Crown angle: 33.7- 35.8 degrees

Pavilion angle: 40.5-41.5 degrees

Girdle edge: 0.7- 2.9% thick

Is cut important?

This is quite the topic of debate amongst people in the trade. Some dealers place a very large emphasis on cut, in an attempt to differentiate diamonds even further; at A Bespoke Life we take a middling approach.

The precise measurements used to determine an 'excellent' cut grade means that is is impossible to differentiate between an 'excellent' or 'good' cut diamond just by eye. You are just never going to see the difference between a pavilion angle which is 43 degree, opposed to 41 degrees, even as a professional grader. And it won't affect how sparkly your diamond is at all. 

However, it is possible to see the difference between the three top grades and the two bottom. Therefore we would recommend buying stones of a good cut or above.

What is triple ex?

Triple ex refers to diamonds that have an excellent grade for cut, symmetry and polish. 

What are polish and symmetry?

Polish and symmetry are what they say on the tin. They refer to the quality of the polished finish of a diamond and how symmetrical that diamond is cut.

These, unlike cut, are applied to all diamonds.

These are also graded on a scale of excellent to poor. 

When it comes to cut sometimes getting a good, rather than excellent, cut can work out a lot better for you in terms of look and cost; this is due to a thing that we in the trade call 'spread'... and no it's not Nutella. 

When a diamond is cut shallower than the ideal 59.9% depth it naturally gets a table that looks a lot bigger, which means your stone looks larger than its weight.

For example, your 1ct round stone may now be 7mm wide instead of the standard 6.5mm. This means that, whilst you haven't got an 'excellent' cut stone, you do now have a stone that looks a lot bigger than its carat weight.

Once again we would recommend putting your money where you can see it and investing in the look of the overall stone than on a cut grade.

In short, we have heard a lot of girls exclaim over the size of their diamond, and not a lot of them boast about the cut grade. 



How are diamonds priced?

Diamond prices are based off the Rappaport list, which offers guidance on the price of diamonds per carat depending on their colour, clarity and carat. 

The Rapp list is only available to the trade but still forms the benchmark of diamond pricing worldwide and is subject to change based on the financial environment, much like other commodities. 

Why have I seen two diamonds with the same grading but different prices?

As the Rapp list only offers guidance on pricing it is possible to find very similar stones for slightly different prices. This is dependent on a lot of things, like where the seller bought the stone themself and for how much. 

However, varied prices can also be due to the quality of the stone. Diamond grading is very subjective and whilst we have defined colours and clarities, within those there is still a scale. For example you may have a stone that was graded a G colour, but actually is more an F colour, this stone would then be priced higher than a stone that was a true G. The same can also be said for clarity. 

How much is a 1ct diamond?

This is sort of like asking "how long is a piece of string?" Because there are so many variables to consider when pricing a diamond it is hard to give a set price on any stone, so we would always recommend contacting us for stone options and pricing. 

However, as a standard rule, for a certified, 1ct F, SI1 stone you should be comfortable receiving quotes of around £5500+. This isn't to say there aren't 1ct stones under this price, but it is a good ballpark figure. 


As diamond prices can vary from shop to shop we recommend shopping around before you settle on any one particular place, and don't be afraid to ask why a stone or piece is priced the way it is.

A Bespoke Life has a mission of transparent pricing, so we are confident we are the best value for money you will find on your search. 


Who certifies diamonds?

There are many independent diamond certifiers to choose from, however some are more reputable than others.

The most respected diamond grading laboratory is GIA and they set the industry standard; however other good international laboratories are IGI and HRD.

There are also local laboratories, such as IGR Global, which give excellent grading results.

Are all diamonds certified?

No, not all diamonds are certified. 

At A Bespoke Life we work with both certified and non-certified diamonds, depending on our client's preference. Our goal is always to get you the best stone for you. 

What are the benefits of a certified diamond?

If you choose to buy a certified diamond you have independent verification of your diamond's grading, which can be reassuring when you are spending a large amount of money on a diamond. 

This certificate can also help with the insurance process as it is proves your diamonds cost. 

So how do I know my un-certified diamond is what you say it is?

Every diamond and gemstone bought and sold by A Bespoke Life is checked by our gemologist and diamond grader, who has years experience in the diamond trade and working as a grader in laboratories. So you can be sure that your diamond is what it is.

We can also offer insurance valuations or diamond grading by an independent laboratory. Please see our FAQs for more information. 

Certified diamonds tend to carry a higher premium than non-certified stones as the certification process can be long and costly. 

We recommend having a look at both certified and non-certified stones in order to get the best stone for your budget. 


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