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The Archduke Joseph Diamond, a colourless diamond weighing 76.02 carats. It sold at auction in November 2012 for a record $21.5 million. The diamond once belonged to Archduke Joseph August of Austria (1872‐1962), a Hungarian prince from the line of the Habsburgs.

Every diamond is unique. This is a beautiful fact about the most exquisite mineral in the world. They are not equal in shape, colour or make-up, all having differing internal features and characteristics. This is what makes diamonds so interesting, so beautiful and so coveted.

Diamonds with a certain combination of factors are more desirable than others. The fact that a diamond is rare – like the Argyle Pink - means it will be more valuable and more sought after than others.

For jewellery professionals it is imperative that they use an efficient way to evaluate and agree on certain factors and characteristics because each diamond must be compared to others in terms of cut, colour, clarity and carat weight. Diamond specialists and merchants use a diamond grading system developed in the 1950s by GIA, establishing the use of the "4Cs" to classify and efficiently describe each diamond.

The 4Cs is the standard that professional jewellers and diamond specialists use to assess and show the quality of a polished and finished diamond. The value of the diamond will be measured based on this standard.


If one or more of the 4Cs is considered as a rare commodity, it will render the value higher. For example, many diamonds have a tint of yellow or brown within its facets. A colourless diamond will rate much higher on the Colour grading portion of the 4Cs because a colourless diamond is much rarer than say a diamond with a light yellow hue. Rarity of course will be a strong determinate of the value of a gem, and the same connection between value and rarity is also used as a criteria to determine a diamond’s worth within clarity, cut and carat weight.

The 4Cs is a method of assessment that has become the recognised international language between diamond professionals and specialists. All diamonds are assessed using this criteria and it is a method that is accepted and understood. Today, this criteria using the 4Cs as a determinate is more precise and more recognised than the quality criteria of almost any other product. The very first diamond grading system was established in India over 2000 years ago and used colour, clarity and carat-weight as the main criteria of assessment. This method must surely be a way of quality assessment that has the longest history and longevity – a pointer to the fact that this method of assessment is highly respected and trusted.



As previously discussed, a colourless diamond will have a much higher value placed on it than a diamond with a hint of colour. Even the subtlest hints will dramatically affect the value of a diamond, despite the fact they may have similar clarity, cut and carat-weight.

In the accepted colour range, a diamond’s per-carat price will be significantly higher the closer it can be compared to colourless.

Of course, diamonds come in many colours, determined by the conditions under which they are formed. The most usual range falls within the colourless to light yellow and brown, and within that range colourless diamonds are rarer and the most coveted, therefore the most valuable.

As you can see from the photograph above, a colourless and clear diamond is totally exquisite in its refraction of light and shows its facets in light and fire. The middle gem is also beautiful but has an almost champagne hue. The right hand gem has a distinctive yellow hue and is the least valuable of the three.

Above is a selection of stones that fall within the scope of a normal colour grade. The stones above represent known colours in the GIA D-to-Z scale and are known as the master-stones. These stones are used by a diamond grader to assess the colour of other diamonds in comparison.

Above is the GIA D-to-Z scale, the industry standard used to colour-grade diamonds with each letter representing a range of colour from colourless to light, in tone and saturation. Within those ranges is the alphabetical spectrum.

Fluorescence is another consideration when grading diamonds. Many diamonds emit a light which we call fluorescence, when exposed to UV radiation. Every diamond will be tested for this light, and when under an UV lamp about 35% of all diamonds will emanate this light. Many diamond purchasers will obtain a diamond because of the amount of fluorescence a stone emits. This light is often associated with the colour blue in gem-quality diamonds. In exceptional circumstances fluorescence can be orange, yellow, white, or indeed in many other colours.

Fluorescence can be an advantage or a disadvantage depending on the original colour of the stone. For instance, light yellow diamonds can become closer to the colourless gem some purchasers aspire to if it emits a strong blue fluorescent light. This is because blue and yellow tend to override one another, being that they are opposites on the colour spectrum. Also, a too strong fluorescence can make a diamond cloudy which will have a detrimental effect on the value of a diamond.



A diamond will be assessed for clarity to find any blemishes or inclusions present in the stone. There are few diamonds that can be termed 'perfect'. Most will have small imperfections which of course affects the value of the stone. A perfect stone is a rare thing indeed, yet they do exist and of course have a very high value.

All blemishes, scratches, inclusions or nicks on the diamond’s surface will affect a diamond’s appearance. Inclusions are usually inside, and one may be able to see tiny pinpricks of carbon deep within the stone. On occasion, other crystals of mineral or tiny diamond crystals may be trapped within a diamond at its formation. These may be left within the diamond when the rough stone is cut and polished by diamond cutting experts.

Inclusions may actually be useful when gemmologists are determining a diamond from the many imitations on the market – an easier task than when examining flawless diamonds. Inclusions can also be helpful when used to identify one stone from another, and have been instrumental in helping scientists when studying how diamonds are formed.

As the above clearly shows, diamonds are completely unique, not only in colour but also how a stone is formed. As with the other 4Cs, clarity is very important when assessing value and is again related to rarity. Most purchasers will aspire to a flawless grade, the top grade as directed by the GIA Clarity Grading System. A 'flawless' grade means that a stone has no visible inclusion or blemishes when determined under a 10X magnification loupe. The stone must be assessed by a grader who has the skill and experience under the GIA specifications.

As we have discussed, flawless diamonds are extremely rare and many jewellery experts have never seen one during their careers. A flawless diamond will command the very highest prices.

There are of course diamonds with inclusions that can be seen with the naked eye. Diamonds in the middle of this and the flawless range make up most of the diamond retail market. The eleven grades in the GIA clarity grading system begin at Flawless and continue through Internally Flawless, two categories of Very, Very Slightly Included, two categories of Slightly Included and three categories of Included.

The positioning of the inclusion is paramount. An inclusion positioned directly under the table of the stone would be far more detrimental to the diamond than one positioned to the side.

Diamond specialists will use terms that are easily recognised when discussing the clarity of a stone. These are very, very slightly imperfect, very slightly imperfect, slightly imperfect and imperfect. Recently the term ‘included’ has been used to replace the ‘imperfect’ term.

To make understanding easier, these terms are now shortened to VVS, VS, SI, and I, and are accepted throughout international diamond communities. Even countries with different alphabets, such as Russia, will use the same abbreviations because of their international acceptance.


The cut of the diamond is a quintessential part of what makes a diamond scintillating, dazzling, superb. When we first see a diamond it is the cut that catches our eye and determines the sparkle and fire.

Cutting precision is paramount and diamonds today are cut to the most exacting standards to keep up with market demands and trends. In the diamond above, the arrow pattern can be clearly seen. The proportions determine light refraction when entering the diamond. A diamond that has been cut exquisitely with great skill and experience will scintillate and make much better use of light entering the stone.

Scintillation ~ Areas of light and dark
Brightness ~ White light reflections
Flashes of Colour ~ Fire

The pattern of a diamond is the contrast of areas of brightness and darkness, the relative size and the arrangement of the facets, and a diamond’s internal and external reflections. Obviously the appearance and proportion of light within the diamond is essential and with expert cutting, a diamond will emit maximum light and scintillation. The GIA Laboratory have realised that certain combinations and variations of proportions of round cut brilliant diamonds will maximize fire and brilliance.

The shape of the diamond is also determined by the cut. Of course the standard round brilliant is very familiar to us, but cuts other than this are known as fancy cuts, fancy shapes or fancies. The shapes all have their own unique names such as heart, emerald, pear, oval, marquise and princess.



Weight and price are connected in the assessment of a diamond’s value, just as they are in any other area of purchasing. Most people would realise that a small diamond will be less expensive than a larger one but there are some surprising indicators when it comes to weighing these precious stones.

The first surprise will be that diamonds are weighed with infinite precision – a diamond weight is termed as carat (ct) and one metric carat is two-tenths (0.2) of a gram, just over seven thousandths (0.007) of an ounce. An ounce contains almost 142 carats. A small paper clip weighs about a carat. A metric carat is portioned into 100 points and a ‘point’ is 1/100th of a carat. Diamonds are weighed to a thousandth (0.001) of a carat and rounded to the nearest hundredth, or point. Fractions of a carat can mean price differences of hundreds – perhaps thousands of dollars, depending of course on the diamond’s quality, determined by the 4Cs.

When a diamond weighs over a carat, the weight is usually articulated in carats and decimals. For example, a 1.04-carat gem would be determined as ‘1 point, oh 4 carats’, or a shortened version ‘1 oh 4’. A diamond that weighs less than a carat will be stated in points as described above. For example, a diamond weighing 0.84 carat will be described as weighing '84 points' or is an '84 pointer'.

The second astonishing fact will be that the connection between the weight, rarity and value of a stone can be startling. When items are being weighed, usually the heavier the item is the more expensive. For example, a kilo of potatoes will cost more than half a kilo of potatoes. Diamonds are not assessed in the same way. It is not hard to understand why someone would think that a much larger diamond would have a much higher value than a small one. Their value, therefore their price is dependent on a number of different assessments – not just weight. A 2-carat diamond for example, may be expected to command a price of $15,000, therefore a 1-carat diamond may be expected to realise half of that value, say $7,500. This is not the case.

The concept is as follows: a large diamond is far rarer than a small one of which there will be some abundance. If something is rare it will command a much higher price because of its scarcity, so a larger stone will not only command a higher price – it will also have a higher carat value.

Four 0.25 carat diamonds weighs the same as a 1- carat stone, yet the 1-carat stone will command a higher price than the four 0.25 carat diamonds. Even if the other quality factors are met equally, the larger stone will still be higher in price.

Often, carat weights become ingrained in a purchaser’s mind and can become symbolic even if all the other grading factors are equal. For example there are ‘magic sizes’ half carat, three-quarter carat and one carat. The difference between say a 98 pointer and a 1.01 carat diamond is insignificant visually, yet most purchasers will opt for the larger stone, even if it means paying a significantly higher price. If the larger stone is only slightly over the magical size of 1-carat it may command as much as 20 per cent more in price.

The beautiful oval shaped diamond below weighs 1.01-carats and has passed the magic 1- carat size.