The Four Cs – And why they're important for you

Every diamond is unique. To calculate its value, experts refer to what they call the Four Cs--Colour, Clarity, Cut and Carat. All of these factors will influence the eventual value of the diamond.

The Colour

Colour Grades used by Royal Diamonds

A diamond can divide light in to a spectrum of colours (like a prism). Colour in a diamond acts like a filter and diminishes the spectrum of colours emitted. The less colour in the diamond, the better the colour grade.

The scale for grading ranges from D which is totally colourless, to Z which is a pale yellow or brown colour. Diamonds that are ‘colourless’ (graded D, E or F) are very rare and demand premium prices. The untrained eye will find it very difficult to distinguish between D, E or F grades.

G, H, I and J are ‘near colourless’ and represent excellent value for money. G and H are sometimes called ‘rare white’ and are the most sought after in the ‘near colourless’ group.

The majority of diamonds we use are colour ‘G’ or above. As you can see, colour G is the 4th highest colour and top of the ‘near colourless’ group. This grade represents great value for money, as ‘colourless’ stones can be very expensive (less than 2% of all diamonds are graded as colour D).

The Clarity

This tells us whether a diamond is flawless—i.e. without any imperfections—or whether there are what the experts call inclusions, small imperfections which are often not visible to the naked eye. In effect, clarity is a measure of the diamond's purity. The majority of diamonds we use are clarity ‘SI1’ or above, which means these natural imperfections are completely invisible to the naked eye. You won’t see any marks in your diamond at all.

IF to VS can be described as luxury grades. Inclusions are difficult to see when using a 10x magnification in good light, and are not visible with the naked eye. Any diamond graded between IF and VS should be sparkly and bright, and within these grades diamonds suffer no noticeable loss of brilliance through reduced clarity.

SI1 and SI2 grades represent excellent value for money. The small inclusions are fairly easy to see under 10x magnification, and there may be some barely noticeable lack of brilliance in comparison. However, you cannot see these small inclusions with the naked eye. Any diamond in these grades will also be bright and sparkly. Untrained individuals will not see the difference between a VS and an SI graded diamond, either in terms of inclusions or brilliance, without using magnification.

P1 Diamonds which fall into the Piqué bracket (P1), by definition have inclusions which can be visible to the naked eye. However, in P1 stones the inclusions should be difficult to see, or very minor, and Royal Bijuterii only use P1 stones with inclusions that are barely visible, if at all visible, to the naked eye. We select the best P1 diamonds so that although they do fall in to the Piqué bracket, you are unlikely to see any marks in your diamond with the naked eye. Any marks that are visible will be very minor and difficult to detect.





IF Loupe Clean Internally Flawless Internally Flawless
VVS1 VVS1 Very Very Small Inclusions No Visible Inclusions
VVS2 VVS2 Very Very Small Inclusions No Visible Inclusions
VS1 VS1 Very Small Inclusions No Visible Inclusions
VS2 VS2 Very Small Inclusions No Visible Inclusions
SI1 SI1 Small Inclusions No Visible Inclusions
SI2 SI2 Small Inclusions No Visible Inclusions
I1 I1 - Piqué1 First Piqué Barely Visible Inclusions
I2 I2 - Piqué2 Second Piqué Easily Visible Inclusions
I3 I3 - Piqué3 Third Piqué Very Easily Visible Inclusions
    Spotted Heavily Included
    Heavily Spotted Very Heavily Included
    Rejection Near Gem

The Cut

When diamonds come from the earth, they look nothing like the polished and cut gems you expect to see in fine jewellery. A lot of work goes in to turning these rough diamonds into perfect works of fiery brilliance. Cut and Shape are often confused - Shape refers to the outward appearance of the diamond (such as round, emerald, princess etc). Cut refers to the reflective qualities of the diamond.

When a diamond is well-cut, light enters through the table of the diamond, travels to the pavilion and reflects from one side to the other before reflecting back out of the diamond through the table. This light creates a flashing effect that we know as brilliance/sparkle.

Cut is described with the following grades: Ideal, Excellent, Very Good, Good, Fair, and Poor

Some diamond certificates do not specifically state the ‘Cut’ grade of the diamond. As we use a variety of independent certificates (AnchorCert, GIA, IGI, IGS and HRD) we cannot guarantee that the cut grade will appear on your certificate. It bears no reflection on the quality of the stone you have purchased if your certificate does not state the grade, as your diamond will always be ‘Very Good’ or better. It requires a trained eye to judge the quality of a diamond cut, and our in-house diamond graders are highly qualified professionals who only select diamonds that they grade as ‘Very Good’ or better. Your diamond will be well-cut, bright and sparkly, we guarantee it!


The Carat

The carat is a measurement of weight, not size. Diamonds are actually valued in terms of their weight, not in terms of their size. The actual size of a diamond can be described in millimetres.

Note – do not confuse 'carat weight' with 'carat/karat' which is the method of determing the purity of gold (e.g 18ct white gold, 18ct yellow gold).

One carat is divided into 100 points – a diamond that is ½ a carat is also 50 points. Carat weight affects the price of a diamond more than any other of the 4 C's. A diamond that is twice the size of another, can be as much as 4 times the price. Larger diamonds are discovered less often than smaller diamonds, which means large diamonds are rare and have greater value. For this reason, the price of a diamond rises exponentionally to its size.

When deciding what size diamond to buy, there are a few things to consider:

  • Your budget – some people suggest 1 - 2 months salary, others whatever you can comfortably afford. There are no strict rules, and it really does come down to what you are comfortable with.
  • Size vs Quality – if your partner prefers larger items of jewellery, and you are working with a budget, you can purchase a larger diamond which is graded slightly lower in terms of clarity and colour. For example, a 0.50ct D VVS1 (luxury grade) will be more expensive than a 0.70ct G SI1 (excellent value grade), even though it is smaller. Opt for the 0.70ct if you think your partner would prefer size over colour and clarity.
  • Finger size – slender fingers make smaller diamonds appear larger. A 1-carat diamond will seem proportionately large if worn by someone with very slim fingers.


The setting of a ring, or any piece of jewellery, is an integral part of its overall design. Whether you are looking for a diamond solitaire, a three-stone ‘Trilogy’ ring or an eternity ring with a number of stones, the way in which the stones are held/set is a significant factor in determining its shape and style.

Claw Setting

This is the most popular of all settings because of the way it enables the maximum amount of light to enter the diamond from all angles, making it appear larger and more brilliant. This is because this setting is composed of very small metal prongs/claws that cradle the diamond so more of the stone is visible. Claw setting is the most popular setting for solitaire diamond rings (typically engagement rings) and the stones are usually easier to clean.

Channel Setting

This setting is mostly used for eternity and wedding rings as the diamonds flow in a continuous stream and can also enhance a central stone. The diamonds are set right next to each other in a metal channel - no metal separates the diamonds so they form a continuous row of stones. The outer ridge of metal is worked over the edges of the diamonds, protecting the stones and providing a smooth outer surface.

Rub-Over/Bezel Setting

A rub-over/bezel setting uses a metal rim/collar that completely surrounds the diamond. This setting protects the edges of the diamond and holds it securely, ideal for those with active lifestyles. When a stone is rub-over set, the metal is pushed/rubbed slightly over the edges of the stone. With a plain bezel set the metal simply encases the stone as opposed to being rubbed over the edges. Both bezel and rub-over set diamonds have a very clean, minimal look.

Invisible Setting

The invisible setting enables you to have what appears to be a large diamond but at a more affordable price, as it is actually made up of a group of smaller diamonds. The stones sit side-by-side, creating a solid surface of diamonds with no metal in between them at all. This technique works by interlocking the diamonds together into a metal framework, using the grooves in each stone’s girdle, thereby creating the impression of one large stone.

Bar Setting

This setting is quite similar to channel setting, except bar setting uses metal plates in between the diamonds that rise to the top of each stone and are therefore visible. Whereas channel setting uses what could be seen as a horizontal metal channel with a row of stones in the centre, bar setting separates each stone vertically with a metal bar. This setting can also be used to hold just one diamond, with a bar placed on two sides of the stone at right angles to the shank/band.

Pave Setting

The word ‘pave’ comes from the word paved. Pave setting uses lots of small diamonds placed very close together, to create an effect similar to a street paved with cobblestones. Each diamond is placed into a small hole that has been drilled into the shank/band. Tiny bits of metal from the surface of the shank are rubbed over the edges of the stones, forming tiny beads which hold the diamonds in place. Pave is one of the more difficult settings to accomplish and requires a highly skilled and very patient craftsman.

Grain Setting

Grain setting is similar to Pavé setting, but the difference is that in grain setting the stones are not ‘paved’ on the surface of the metal. The stones are set in a single file, one next to the other.

Tension Setting

This setting uses the pressure of the shank/band’s metal to hold the stone firmly in place, between two open ends of the metal mounting. The metal grips the diamond by the girdle on each side and we use a bezel for added protection to tightly hold the stone. This technique suspends the stone in the shank and is a popular, modern choice of setting.

Diamond Shapes

There are various shapes a diamond can be – round, emerald, princess and radiant to name a few. Shaping a diamond from a rough stone can take an hour or a year depending on the size and quality of the stone. Smaller stones are more difficult to shape and cutters must have patience and great skill to make the delicate cuts that are necessary to give a diamond the greatest possible sparkle and brilliance.

Round Brilliant Cut Diamond

This shape accounts for over 75% of all diamonds sold today. Round is the most popular shape used for an engagement ring, and of these the round brilliant cut is the most commonly chosen. It’s 58 facet-cut achieves the maximum brilliance a diamond can have, maximising the reflection and refraction of light. Diamonds cut in this way have more depth than width, and can therefore seem smaller than other finely cut diamonds, but they are the most brilliant of all shapes.

Princess (Square) Cut Diamond

This is one of the most popular fancy-shaped diamonds and is popular for engagement rings. The princess cut, invented around 30 years ago, is the most important new shape/cut since the perfection of the modern brilliant cut over 60 years ago. The princess cut is essentially a square version of the round brilliant cut, known technically as a square modified brilliant cut. It is a style of cutting that improves the faceting of square/rectangular stones to obtain maximum brilliance from the diamond, as well as making any inclusions/flaws in the stone less visible.

Emerald Cut Diamond

This shape was originally developed for cutting emeralds, until it was discovered it was suitable for other stones. An emerald cut diamond can be extremely stunning. It may not have the sparkle of a round brilliant cut, but because of its long lines it tends to produce more dramatic flashes of light. It is more scintillating than brilliant, and highlights the clarity of the diamond. The emerald cut shape is rectangular with cut corners, and is one of the most elegant and sophisticated diamond shapes. Emerald cut diamonds are less expensive than round brilliant or princess shapes.

Radiant Cut Diamond

This shape is a cross between a princess and an emerald cut. It combines the best features of the round brilliant cut, the elegance and trimmed corners of an emerald cut and a squarer shape more similar to the princess cut. Radiants are similar to emerald cut stones in their shape, but the faceting is different making the diamond more brilliant. This cut has 70 facets to maximise the brilliance of the diamond.

Marquise Cut Diamond

This shape was commissioned by Louis XIV in France, and was based on the smile of the Marquise de Pompadour. It is a variation of the round brilliant cut - elongated with pointed ends. A marquise diamond is beautiful when used as a solitaire or when enhanced by smaller diamonds. This shape can maximise carat-weight, making the diamond appear much larger, and tends to make your fingers appear long and slender.

Pear Shape Diamond

Pear shaped diamonds are often called ‘teardrop’ diamonds because of their shape. This shape is a combination of the round brilliant and the marquise, a fiery cut with elegant lines and lots of sparkle. Whilst not a traditional selection, pear shaped diamonds make beautiful engagement rings either as a solitaire (single stone) or as shoulder stones either side of a central stone.

Asscher Cut Diamond

The asscher cut was developed by the Asscher Brothers in Holland in the early twentieth century, and is gaining popularity again today. It is often referred to as the ‘square emerald cut’ - because it is square with wide step facets and cropped corners. This cut is designed to draw your eye into the stone, and whilst not a traditional selection, asscher cut diamonds are now very fashionable for engagement rings.

Baguette/Tapered Baguette Diamond

Baguette cut diamonds are oblong/rectangular, and are similar to emerald cuts but without the cut corners (which make emerald cuts octagonal rather than oblong). Rectangular shaped stones are usually cut in steps, and are therefore known as step cut. The earliest jewellers used this simple cut for many gemstones including diamonds because it was relatively easy to cut with the limited tools available years ago. Baguettes make good stones for eternity rings as well as in channel settings, as unlike round stones, they can be set without leaving any gaps between the diamonds. Tapered baguettes are frequently used as shoulder stones to enhance a central stone of another shape.

Diamond charts

Round diamonds

Carat Weight Size (mm)



Princess (square) diamonds

Carat Weight Size (mm)

1.5 – 1.75


Emerald cut diamonds

Carat Weight Size (mm)


3.1 x 2.1
3.9 x 2.1
4.6 x 3.4
4.9 x 3.6
5.2 x 3.9
5.9 x 4.4
6.5 x 5.0
87.5 x 5.5

Marquise diamonds

Carat Weight Size (mm)


5.5 x 3.1
6.3 x 3.5
7.0 x 4.0
8.0 x 4.0
8.5 x 4.5
9.0 x 4.5
10 x 5
12 x 6.0
13 x 6.5

Pear shaped diamonds

Carat Weight Size (mm)


5.1 x 3.5
5.3 x 3.7
5.9 x 4.2
6.6 x 4.5
7.3 x 4.7
7.7 x 4.9
8.5 x 5.5
9.8 x 6.2
10.5 x 7.0