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The 4 C’s – How To Buy A Diamond

Using Your Knowledge Of The Four C’s And Without Paying A Premium

If you have entered the realm of wanting to purchase a diamond then you need to educate yourself as much as possible to understand what you are getting and if it is a indeed a good deal – many high street jewellers will encourage you to purchase the diamonds that they have in stock as opposed to sourcing a stone to suit your requirements.

Start by understanding what it is you want from a diamond especially when you look at it; do you want the diamond to sparkle, do you want the diamond to be bright and white, or do you want the largest diamond that your budget can buy you? Unless of course you have an unlimited amount of money to spend on a diamond, you will find that at some point you will have to compromise on one of the four C’s.

The 4 C’s

  • Colour
  • Clarity
  • Cut
  • Carat

The Colour

Or rather – the lack of colour!

When buying a diamond, with the exception of purchasing a fancy diamond, you want your diamond to be as free from colour as possible. The diamond colour grading system begins alphabetically from D and goes right the way through to Z. Anything past Z and you have entered the fancy colours of a diamond.

The colour is an important visual characteristic, the higher the colour grade, the brighter and “whiter” the stone appears. The GIA (Gemological Institute of America) are a diamond certification body and use sub-groupings to further simplify the colour grading system:

  • Colourless are grades D-F
  • Near Colourless are grades G-J
  • Faint are grades K-M
  • Very Light are grades N-R
  • Light are grades S-Z

What colour grade should you look for when buying a diamond?

Two colour grades apart – left is an E colour diamond, on the right is a G colour diamond.

A diamond which is a colour grade D is deemed as the best and most rare, therefore you pay a premium for a stone of this colour grade. Unless you have a highly trained eye, and have two loose diamonds sitting next to each other on a plain piece of white paper, at least 3 colour grades apart – it is very difficult to see the subtle colour difference. However is can greatly affect the price of a diamond.

Our recommendation would to be to stay in the “near colourless” grades and the “colourless” range, preferably grades H/G colour and above. Diamonds in the near colourless range will be sensational and bright but without the high price tag. It is not a necessity to have a D coloured diamond, especially when even one colour grade down will look almost identical but may save you a lot of money.

The Clarity

Diamonds are created deep within the earth’s mantle in extreme conditions. The environments in which they develop in are far from controlled and so inclusions and blemishes can form and are present in almost all diamonds. Flawless diamonds are exceptionally rare thus there is a premium should you wish to acquire such a stone. Some jewellers may have a negative view on inclusions and blemishes, but ultimately they are after all, natures hallmark and fingerprint.

The grades for clarity are similar across many certification bodies, with slight variations. The grades are based upon how free from inclusions and blemishes a diamond is using 10X magnification. The clarity is graded with a number of factors in mind such as placement, the size of the inclusion, the number of inclusions, the colour of the inclusion as well as a whole range of other factors.

A diamond viewed through a 10X magnification loupe.
The clarity grades from the IGI (International Gemological Insitute):
  • Flawless – F
  • Internally Flawless – IF
  • Very Very Slightly Included 1 & 2 – VVS1 & VVS2
  • Very Slightly Included 1 & 2 – VS1 & VS2
  • Slightly Included 1 & 2 – SI1 & SI2
  • Imperfect 1, 2 & 3 – I1, I2 & I3


It is advisable to stay above the imperfect range unless it is a specific look that you are going for, as the more heavily included your diamond is, the less valuable it is – so keep this in mind when purchasing your stone.

Slightly Included diamonds are our personal favourite as you can absolutely have a stunning slightly included diamond which is perfectly eye clean and does not impact on your diamonds fire or brilliance. An eye clean stone is a stone which has no visible inclusions, especially in the top table facet, from a distance of circa 6 – 8 inches away from an unaided eye.

An IGI certified diamond.

If you wish you to have a higher clarity diamond, it will cost extra and it is not a necessity, as all you need a diamond to be is eye clean. Otherwise you are paying a premium for a characteristic you cannot physically see without the aid of 10X magnification and a trained eye.

The Cut

Would you like your diamond to sparkle – should have been the title here! A diamond is known for its brilliance, fire and scintillation, which are a direct result of how well it has been cut and how good the proportions, symmetry and polish are. The cut grades are a measure of how well a diamond interacts with light and the light return that it gives.

Round Brilliant Cut Diamond
The cut grades from the IGI are:
  • Excellent
  • Very Good
  • Good
  • Fair
  • Poor


You do not, under any circumstances, wish to purchase a poor or a fair cut diamond. This will simply be a diamond which is either cut too deep or too shallow, which results in light leaking out of the sides and will be a lifeless diamond. It would be like a person without a personality – the sparkle is the epitome of a diamond.

The cut does not refer to the shape of the diamond, however the shape and cutting style plays a role in the overall cut grade. The most popular shape of a diamond is a round diamond, but a diamond can be cut in numerous different shapes including an oval, a marquise or even a heart shape!

The perfect cut arrangement originated in 1919 by Marcel Tolkowsky. He calculated the specifics to achieve a perfect cut diamond, the optimum number or facets, their perfect placements, along with the exact and best proportions to provide the maximum light return and dispersion. This cut is one of the most famous diamond cutting styles, known all over the world and is still used to this day – the round brilliant cut. Other cutting styles include the step cut and mixed cuts.

The Carat

The carat is the measurement of the weight of a diamond. The carat weight is a metric measurement divided into 100 points – the precise weight of a 1 carat diamond is 200 milligrams. To some, a diamonds carat weight can be one of their main priorities. However, if you have a very strict budget this could mean that you are compromising too heavily on another characteristic in order to achieve the biggest diamond for your price range.

You can be clever when it comes to choosing the size of your diamond. For example, if you are interested in a 1 carat diamond and you include in your search a diamond between the ranges of 0.90ct – 0.99ct, it can look very similar in size to a 1 carat diamond and may even spread the same. By lowering your carat weight search, you could find the perfect diamond of a similar size, yet save yourself a lot of money. The spread of a diamond is a measurement in millimetres – an average 1 carat measures around 6.4mm.

Avoid, where possible, benchmark carat weights such as 0.50ct, 0.75 and the definitive 1 carat mark. Diamonds are sold on price per carat basis, and a typical consumer wishes to be able to say that she has a 1 carat diamond solitaire engagement ring, therefore a 1 carat stone costs a premium. Unfortunately there is no steady correlation between the price of a diamond and its carat weight. Discuss with your local jeweller as to what carat you are aiming for and what could look like a similar sized diamond, but without the premium price.

The 5th C?

The Certificate of Course!
Which diamond certificate should you look for?
GIA Diamond Report

The GIA are undoubtedly the most globally recognised diamond graders and have a fantastic reputation; however there are other highly reputable and well known certification bodies such as HRD (Diamond High Council) and the IGI (International Gemmological Institute). The IGI were established in 1975 and have worldwide laboratories including the oldest laboratory in Antwerp, and the HRD were established in 1973 and pride themselves on integrity and developing new ways to screen and examine diamonds.

IGI Diamond Report

Despite how they may seem, diamond certificates are actually not hard written scientific facts but are ultimately an opinion from trained diamond graders. I would advise looking at all reputable diamond certifications with your diamond as this could also save you money when purchasing a loose diamond or an engagement ring. GIA certified diamonds due to a number of reasons, but mostly down to incredible marketing, demand higher prices than the exact same diamond but with an alternative certification.

A standard HRD certificate includes the following information:
  • The date of the diamond report
  • Report number – referring to the laboratories database
  • Shape of the diamond
  • Measurements of the diamond in millimetres
  • The carat weight, the colour grade, the clarity grade and the cut grade – the important four C’s!
  • The finish, polish and symmetry of the diamond
  • The fluorescence of the diamond
  • An inclusion plotting diagram – typically only present if a diamond is over 1 carat
  • HRD cut, colour and clarity grading scales


A diamond exhibiting medium blue fluorescence.

A natural phenomenon is diamond fluorescence which refers to when a diamond emits a glow, typically a blue glow, when under an ultraviolet source such as a black light or strong sunlight. Not all diamonds have fluorescence, only around 25 – 35% of diamonds show a degree of fluorescence. When looking for your perfect diamond we advise to look for diamonds which have none, faint or slight fluorescence. Strong fluorescence can have a negative visual impact on the diamond by making it appear milky or cloudy to the naked eye.

Ask Your Local Jeweller

If you are in the midst of looking for a loose diamond or a diamond engagement ring, you should ask your local jeweller questions on anything you do not understand about the four C’s. Do not be pressured into buying a diamond you do not wish to own, even if you think it is a bargain – it could be a bargain for the wrong reasons.

We Can Help You Too!

We have access to over 1 million diamonds, and so if you would like to discuss purchasing a loose diamond from us, or you are interested in creating a bespoke diamond engagement ring – we can help!

A collection of our bespoke diamond engagement rings.

Please do not hesitate to contact us via email

To see or follow our work, please visit our Facebook page or find us on Instagram.

We can create you the perfect diamond engagement ring and tailor it specifically to your personal preferences and your price range. We can take your dream and make it a reality.


The Formation Of Gemstones & Organic Gems

True and beautiful natural gemstones owe their development to wonderful natural causes of the world, of which there are many varieties; mineral origin found in rocks, in gem gravels from these rocks, or organic gems from plants and animals – all with no intervention or production from man. For natural mineral gemstones to occur, a combination of temperature, pressure, oxygen, chemical elements and time are all needed for their formation. Different environments and processes produce a variety of gemstones with varying chemical structures and crystal structures which produce such diverse attributes of hardness, colours and optical qualities.

Organic gems have been adored for hundreds of years and are from living things such as plants and animals. Amber is an organic gem of hardened and fossilised tree resin from pine trees, typically from hundreds of years ago. Amber can have inclusions such as insects that were trapped inside the resin as it was forming – such inclusions of insects can increase the amber’s worth. Pearls are another divine and organic gem from the produce of molluscs, either fresh water or salt-water. Starting with a foreign body entering and becoming an irritatant to the mollusc, this causes it to protect itself by producing a layer of nacre to coat the foreign body – this ultimately produces the pearl. Other organic gems include coral, shells, ivory, jet and even tortoise shell.

Mineral gemstones are formed from rocks, of which there are three main types: Igneous, Sedimentary and Metamorphic rocks. These processes form the rock cycle as they are all in a constant state of change, as well as interlinking with sub cycles and cross interactions. The varying types of rocks have their own processes which can change a rock or gemstone’s chemical and physical properties. The earth has several layers that were formed 4.5 billion years ago; the crust, which makes up 1% of the Earth’s volume, is from 3 miles to 25 miles deep, the mantle is said to make up 80% of the earth’s volume, and finally the core which has a solid inner and liquid outer layer – all of these layers and processes produce the stunning gemstones that are found.

  • Igneous rocks – the solidification of magma, the magma rises through the cracks of the earth’s crust and dependent on whether or not the magma reaches the surface, ultimately leads to intrusive or extrusive igneous rocks. Intrusive igneous rocks are formed through the cracks of the earth’s crust or volcanic pipes which are able to cool slowly under the earth’s surface giving, with time and perfect environmental factors allow the magma to form large crystals. If the magma erupts onto the earth’s surface it is then deemed as lava and depending on the rate of cooling, the extrusive rocks can produce medium to very small crystals. Igneous rock gemstones include amethyst, citrine, emeralds, aquamarine, garnets, moonstone, diamond, topaz and zircon.
  • Sedimentary rocks – the consolidation of layered sediments, with igneous rocks on the earths surface and due to factors of erosion and weathering can mean that they are broken down into smaller pieces which are then transported by the wind or water and deposited into pockets. Eventually these pockets are built up into layers through continuous cycles of erosion and deposited on top. Eventually with the layers building over time, pressure begins to build up on the bottom layers causing them to become compact, producing chemical and physical changes, altering its state, and producing new rock formations. An example of a sedimentary rock gemstone would be opal or zircon.
  • Metamorphic rocks – these can be either igneous or sedimentary rocks under tremendous heat and pressure. This happens within the earth’s crust, over time or from direct contact with magma, and can result in the change of the crystal structure. This forms new rocks and minerals, producing new gemstones such as Jade, Turquoise, Ruby, and Sapphire.

The time and effort Mother Nature puts in to create these magnificent gems, what better way to show these gemstones off, than by using them in elegant pieces of fine jewellery…

We have access to over 1.5 million different loose diamonds worldwide. Loose diamonds as the term infers means that the diamond is not in a setting.

There are a great many reasons to buy a loose diamond. Some people like to give loose diamonds as a present so that the recipient can build a ring around the diamond. Loose diamonds can like any other diamond be certified or uncertified but we at International prefer to sell certified stones.

One might ask is there anything wrong with an uncertified loose diamond. The answer is sometimes no as the diamond can look on the face of it as good as any other diamond but often the mine will have decided that it is not going to make certain criteria and that these stones will be sold off at a discount. Sometimes an uncertified loose diamond can be available at a very substantial discount so do not rule them out. Most reputable dealers offering loose diamonds will offer to upgrade them to loose diamond later on when the finances improve.

Some people prefer to sacrifice quality for size and the trick is to find a happy medium when buying your loose diamond certified or not.

In the modern world diamonds can be transported quickly and we can get a diamond from most parts of the earth within days! Once a loose diamond has been found we can build a setting to fit around it and this is done by creating a CAD. CADS or Computer aided designs often look unattractive because of their sheer size. Do not let this put you off the designs have to be of scale in order for the cad operator to be able to see them properly.

Good luck with finding your loose diamond. We supply both loose diamonds and the complete ring and are happy to supply either.




People often think that diamond mines must make a fortune from the loose diamonds they mine. They think that the profits from uncut diamonds must be massive. The reality is more different.

Did you know that 85 per cent of the diamonds that are mined are only suitable for Industry. This leaves us with 15 per cent available for the jewellery industry and imagine refining that into colour grades cut grades and clarity and you will have an idea as to how imperfect the average diamond is. It is only the really good quality stones that make it into the top dealers and suppliers and this is a tiny percentage.

Only one diamond in a million is a carat or more. A one carat diamond can often cost 3-5 times the price of a half carat diamond. The average mine costs about 1 billion to identify and a further 1 billion to develop. Some of the stones are up to 5 miles below the earth’s surface.

The young diamonds are 100 million years old and some of the older ones up to 200 million years old-so the next time you see a diamond show some respect! Your diamond will significantly in your new bespoke ring – wouldn’t you, having been in the dark for 100 million years or more!



We thought you might be interested in some of the following facts about diamonds:

  1. It takes approximately 250 tonnes of earth to obtain a 1 carat diamond!
  2. Only 1 diamond in a million is a weighs a carat or more.
  3. 85 per cent of diamonds mined are not suitable to be used in jewellery.
  4. Only a diamond can scratch or polish another diamond.
  5. Most diamonds are over three billion years old-some of the youngsters are 100 million years old!
  6. Most diamonds are formed more than 100 miles beneath the earth’s surface.
  7. At one time diamond colours were referred to only as A and B. As cutting equipment got better and it became easier to grade diamonds the range was expanded. In order to avoid any confusion with the old scale colours were started with D being the best are running all the way to Z.

We hope you enjoy some of these facts!