The 4Cs of Skydiamonds

Skydiamonds are made with love. The 4Cs are imbued into every step of the journey, from sky to shop. The 4Cs characterise the nature and quality of an individual diamond: colour, clarity, cut and carat weight. The 4Cs represent the universal grading system for all diamonds.

Using the 4Cs as a guide, you can be sure you’ll purchase something that you’ll cherish for eternity.

Diamond Cut

What is a diamond cut? Diamond cut is a grading system which represents not shape, but sparkle. It affects the polish, balance and symmetry of a diamond. This is down to the proportions of the diamond once cut, including width, table and depth.

All of this will change the way your stone gleams and shines. The better the cut, the more wonderfully it will refract the light and showcase the nature from which it came. Experienced diamond cutters will know exactly how to get the best sparkle from a stone.

The different types of shine

  • Brilliance: Flashes of light that bounce within the stone giving the effect of a prism.

  • Fire: Colour that dazzles within the stone due to light dispersion, from reds to blues.

  • Scintillation: The playful spectrum of white light on the surface and coloured light deep in the stone.

The GIA diamond cut grading system

Super ideal

These stones are only the best. They have the most beautiful proportions for brilliance, fire and scintillation


A stone with high brilliance, scintillation and patterns of light and dark areas. They look as stunning as a super ideal cut but may have more light escaping

Very Good

These diamonds still have high brilliance and scintillation, but its pattern might mean it’s darker in the centre and at the edges


Diamonds that are slightly darker and have less scintillation. Weight ratio can also have an impact: if it weighs more than the average gem with the same diameter, it will score lower on the scale


A diamond graded ‘Fair’ will have little scintillation or brilliance, and appear darker than ‘Excellent’ and ‘Very Good’ stones


These stones have very little brilliance or scintillation. They are often murkier, with some having black centres. Poor weight ratio can lower the stone’s grade

Cut vs shape

Cut and shape are often used interchangeably, although they are technically different. The cut refers to the way the light reflects and plays with the stone’s facets. Shape is more common to talk about and it is the silhouette of the stone.

Cut is, however, just as important. It must be precise to get the right sparkle. Cut is graded by seven components: brightness, dispersion, scintillation, weight ratio, durability, polish, and symmetry.

Length to width ratios are used to determine symmetry. Anything over 1 is asymmetrical or elongated. For example, a pear-shaped diamond is not perfectly symmetrical. That’s why each diamond shape has a different ideal ratio. Anything outside of this ideal ratio suggests the diamond is not able to hit and reflect the light in the right way.

The different diamond shapes

This may be the most important part of choosing your diamond or Skydiamond. Which shape do you want? This is where people can choose something that is authentically their style.

Round, Princess, Emerald, Pear, Cushion, Oval, Marquise, Heart, Asscher

Want to know the benefits of each cut?

Diamond Carat

What is a diamond carat? This word comes from the Mediterranean ‘carob’, a seed used to weigh diamonds. These seeds are identical in size and weight and so this became the unique measure of diamond weight.

How a carat is measured

A Skydiamond is measured in carats, one of which equals 200mg. They are further divided into minute measurements so jewellers can be absolutely precise about each diamond weight.

This doesn’t necessarily indicate size as the density and shape of the stone also come into play. Total carat weight (TCW) will also be used to represent the entire weight of all stones in your jewellery piece. For example, a solitaire ring with diamonds in the shoulder will display a TCW.

How a diamond is weighed

A diamond is either weighed by hand or using a specific scale (this is much more common). These scales are exclusively for weighing diamonds. Jewellers use a point system to indicate weight also:

  • 50 points is ½ carat

  • 100 points is 1 carat

  • 200 points is 2 carats

How carat affects price

Carat does affect the value of a diamond. Alongside cut, clarity and colour, this adds to the quality of the product. It’s also not necessarily a linear relationship between cost and carat. Bigger diamonds are considered more rare and therefore more valuable. As carat doesn’t indicate size specifically, you may get a higher carat diamond that costs less than a lower carat, larger sized diamond.

Critical weight is important for loose diamonds. Once it hits a critical weight, the price gets higher as standard. These weights are 0.50ct, 0.75ct, 1.00ct, 1.50ct, 2.00ct, 3.00ct, 4.00ct, 5.00ct and 10.00ct.

Ultimately, you can find your perfect sized diamond within your budget by changing the carat.

Get a full guide to diamond carats

Diamond Colour

What is diamond colour? Colour may be a misleading term, as it actually measures the lack of colour. The colour aspect refers to how much ‘imperfect’ colour - yellow, grey or brown ‘tint’ - appears within the stone. The absence of colour in a diamond contributes to its value, colour grade and appearance. The less colour, the more valuable it becomes.

Fancy coloured diamonds

Diamonds have several measures of colour. Hue indicates the true colour of the diamond, for example blue or pink. Tone speaks to how light or dark a diamond’s colour is. Saturation is then the colour’s intensity.

Typical colours include yellow, brown, pink and grey. These are included in the diamond colour scale. Fancy-colour diamonds have their own scale as they come outside of the normal colour range, encompassing all colours of the rainbow.

The diamond colour chart

The standard colour chart from GIA measures diamond hue in colourless diamonds. This ranges on a scale from D to Z. Colourless diamonds will appear icy white while light yellow shows a noticeable yellow hue.

How colour is measured

The colour of a diamond is determined by inspecting the stone face down against a pure white surface. Traders will do this with specific lighting and viewing conditions in place. The distinctions can otherwise be hard to see.

What colour should you choose for your engagement ring?

Diamond Clarity

What is diamond clarity? Clarity refers to the purity of the stone. During the formation process, diamonds, natural, lab-grown or sky mined, can be marked in small ways internally or on the diamond. These marks are called inclusions. They mean that each diamond is totally unique.

The clarity grading scale

There are primary gradings and then within these, there are sub-categories. These sub-categories indicate how prominent a blemish is to the naked eye.

Flawless (FL)

Flawless stones have no inclusions or blemishes

Internally flawless (IF)

Internally flawless stones have no internal inclusions, but some small surface blemishes

Very very slightly included (split into two gradings; (VVS1 and VVS2)

VVS inclusions exist but are very slight and only just identifiable by a trained diamond trader. VVS1 has a higher clarity than VVS2

Very Slightly Included (split into two gradings; VS1 and VS2)

VS stones have inclusions that are marginally easier to identify by diamond traders than VVS stones. VS1 diamonds have a higher clarity than VS2. VS1 stones have inclusions that are invisible to the trained eye without magnification, whereas VS2 stones have inclusions that – very occasionally – are visible

Slightly Included (split into two gradings; SI1 and SI2)

SI stones have inclusions that are either easy or very easy for a trained grader to identify. SI1 stones have a higher clarity than S12

Included (split into three gradings; I1, I2 and I3)

Included graded stones have inclusions that are undoubtedly clear to a diamond grader under 10x magnification

How clarity is measured

Most defects however are invisible to the naked eye. Gemmologists inspect diamond stones under a 10x magnification to look for blemishes.

Clarity is evaluated by the following measures:

  • Size – The size of an inclusion is probably the most critical factor that determines the clarity score of a diamond. The bigger the inclusion, the lower the clarity score will be.

  • Number – The more internal flaws a stone has, the lower the clarity score.

  • Nature – This factor refers to the nature of any inclusions on a diamond. This includes the depth and characteristics of inclusions that can be seen within the diamond. The impact this has on the diamond’s durability is also taken into account.

  • Location/Position – Where in the stone is the inclusion? If it is closer to the centre of the table (the largest facet of a diamond), then the imperfection will be more visible and therefore the clarity score will be lower. If an inclusion is located near the girdle – or outer edge – then it will be less visible and won’t have as much of an impact on clarity as an inclusion near the centre table or pavilions – the part of the diamond that is prone to reflecting, which would exacerbate any inclusions. This might be prominent on Asschercut diamonds, which are deeply cut and have an obvious central focal point. For brilliant diamonds, inclusions may be less obvious as they are cut to reflect a maximum amount of light.

  • Relief and colour – Relief refers to the noticeability of an inclusion in contrast with the rest of the diamond. If there is a higher relief, the colour will also be affected. Together these will lower a diamond’s clarity score.

Different types of inclusions

No diamond will be entirely pure, but the degree of these blemishes will affect how clear the diamond appears. It may not sparkle as much! There are various types of inclusions and each of these affect the transparency of a diamond differently.

Different types of inclusions are:

  • Cloud inclusions

  • Graining inclusions

  • Cavity inclusions

  • Feather inclusions

Read more about diamond clarity

We offer cut, colour, clarity and carats

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