Diamond Education: Grading Diamonds and the 4 C’s
Diamond Grading Information and Terminology.
The value of a diamond is determined it’s weight and quality. These elements are often referred to as the “4C’s”. The 4 C’s are the diamond’s Clarity, Colour, Cut and Carat Weight. The combination of the quality elements is assessed to determine the value and cost of a diamond. In addition to the 4 C’s, there are about 20 other factors that affect the price of diamonds. A good diamond education is essential. It will help you to understand why a diamond costs what it costs.
After Carat weight, Clarity is often assumed to be the most important of the 4 C’s. In fact, Colour and Cut can have a profound visual effect on the appearance of a diamond. It is for this reason that Excellent cut is the most highly sought after cut grade.
The best diamond for a client is usually one that is a balance of all the quality elements. Unless your budget is unlimited, it is not necessary to be at the very top of each area of the grading standards. A good diamond education will help you select a diamond that will be a great balance in the diamond grades for the budget you have available.
Carat is the unit of weight for all gemstones. The word “carat” originates from the seed of the carob tree pod. The tree is found in tropical climates. These seeds were historically used by merchants to balance scales to weigh precious gems.
One carat is subdivided into 100 “points”. Therefore, a diamond measuring 75 points is 3/4 carat in weight or 0.75 ct.
A diamond’s clarity is determined by the number, nature, position, size and colour of internal characteristics called “inclusions”. Surface features called “externals” also form part of the assessment. These naturally occurring irregularities form in the diamond in the liquid magma (volcanic rock) within which the diamond was created. Diamonds are mostly pure carbon. As they crystallise, other minerals nearby or other particles of carbon forming at a different rate may have become trapped within the cooling mass, creating the features we call “inclusions”.
Clarity is measured on a scale ranging from flawless, (Fl) to heavily included (P3). The final clarity grade is determined by how visible any inclusions or externals are. This is assessed by using a 10 X magnification jewellers loupe. The lighting must be special diamond lighting. The grader (in a reputable laboratory) should be an experienced gemologist.
Below is a Grading Chart. It illustrates the typical size and position of the inclusions a diamond may have in order to gain a particular clarity grading. In order to display the inclusions, they are illustrated in red. However in the actual diamond, they will be either clear, white, black or grey in appearance.
Clarity Related Terms;
Externals, if present, occur on the surface of a diamond. They are the result of the environment the diamond has been exposed to either naturally or during the mining or cutting process.
When an inclusion is near the surface an extra facet may be cut to eliminate it. This may raise the overall clarity grade of the stone. In most cases extra facets are difficult to detect with the naked eye.
This is a small part of the original rough diamond’s surface, typically around the girdle, which is left on the polished diamond.
This is a naturally occurring characteristic formed while the diamond crystal grows. It does not necessarily occur on the diamond’s surface, it is part of the stone’s structure and cannot be removed from the diamond without re-cutting the stone.
Inclusions are characteristics that occur within the diamond itself. Almost all internal inclusions are naturally occurring.
Here are some of the most common types of inclusions:
These are very minute crystals of other minerals or materials that were absorbed while the diamond was growing. Depending on what type of crystals they are, they may be transparent or may have colour to them. Under a microscope, they often look like little round bubbles. In the higher grades, they are undetectable to the naked eye.
These are included crystals that are so small that, even when magnified to 10X, they still only look like little dots. They can sometimes be difficult to find.
These look like extremely slender tiny needles even under a microscope. They are inclusions that have caused the crystal to follow in the direction of the grain.
A natural is an included diamond crystal that reaches from the inside to the surface of the polished diamond.
Chips are usually a small, very shallow opening on the surface of the diamond. This could be a naturally occurring opening in the diamond or the result of damage the stone has received.
This is a larger version of a chip. These are sometimes created by the person doing the cutting when an included crystal near the surface of the rough diamond is removed. This may leave a cavity behind.
Feathers are small features within a diamond. Stress has usually caused this during the formation of the diamond. They can occur inside the diamond or at the surface. The term “feather” comes from the fact that, under magnification, these features often seem to have a distinct, feathery shape to them.
Internal graining is a naturally occurring phenomenon in some diamonds. This usually occurs within the diamond’s internal structure, extremely fine lines may be seen under magnification.
Clouds are a cluster or a number of extremely tiny inclusions that are too small to be distinguishable from one another. This characteristic may give that area of stone a clouded appearance, but also may have no visual impact on the diamond at all. This is where a good diamond education is essential so that you are aware of potential issues.
This diamond shows many of the issues and inclusions that are outlined in the text above. Diamonds of this type are commonly found in low-end retail stores. With a bit of diamond education under your belt, you can see that this diamond is well below the Ellissi recommended standards.
The highest grade of diamond has no colour at all. Increasing degrees of colour or tint are measured on a scale ranging from no colour at all (D) to significantly tinted. A, B and C are not used in diamond grading, as before an internationally recognised system was established, these letters were already used to grade coloured gems (sapphires, rubies etc.). So as not to confuse the two systems, diamond grading colour starts at “D”. Beyond “X”and “Y” is the range where the diamond’s colour is vivid and rich. These are called “fancy colours”.
Diamonds of known colour are used as comparison stones for colour grading. These are known as “master stones”. The diamond to be graded is compared to the master stones under a special light.
Colour grade in diamonds is the amount of tint a diamond may have – think of it like a car windscreen, and the many degrees of tint possible. If you see no tint, this will be “D” colour, a little tint will be E, slightly more tint, F and on it goes. The differences are subtle and often only just visible to the eye in the top levels when the diamonds are viewed next to each other, side by side ( unset ).
The above explanation of colour grading is basically the way it’s done for most diamonds. White diamonds are actually graded for colour through the back of the diamond from the side against a white background. Because when viewed in the normal way, from the top of the diamond, as it would be in a ring, the cut design can have an effect on the perceived colour. However coloured diamonds like “fancy yellow” etc are graded from the front as the eye would see them, the right way up if you like. Everything relating to diamond grading is complex so stay with me.
Most certifying labs will grade diamonds by viewing it face down on a white card, assuming it is not thought tinted enough to be a “fancy colour” face up. So they are looking at the body colour of the crystal. attempting to minimise the effect of the “cut” on the colour of the diamond. This level of “tint” is set against a master set of graded sample diamonds of known colour.
Guess what, nature likes to complicate things so diamond education tends to get pretty wordy. As I have said we generally grade colour from the back, but diamonds can actually have a colour of say “F” and face up to look more like G/H. They may even have a slight brown tinge when viewed face up. This would only be noted in the grading report if seen by the graders when the diamond is viewed from the side, so it would get the “H” it deserves. This is an issue that we always check with our cutters as it is not covered correctly in certification at the moment.
Disparities in grading assessments can occur as diamonds are so unique in the way they refract light, also because of the subtleties in a different light source. And of course too, different people view colour in different ways. In fact, the same diamonds have been said to grade differently from north to south of the equator!
The cut is sometimes the forgotten “C”. In fact, a good cut is critical to the diamond’s appearance. A good or fine cut (sometimes referred to as “make”) ensures that a given stone has maximum brilliance and sparkle. This is often compromised when the stone is cut purely for weight and size alone.
One of the most important features in a diamond’s cut is the angle of the facets in the lower pavilion (the portion of the stone below the girdle). This determines the angle at which light is reflected back to your eye. This gives the stone its sparkle and play of rainbow colours. If a stone has been cut to maximise this effect then an excellent display of colours can be seen within the stone.
Some stones may have been cut with more of an emphasis towards size and weight. This is not always a good thing as changing the proportions will cause light to be dispersed in directions other than back to the eye. This results in less vibrant looking diamonds. They may still be graded highly for colour and clarity, as this poor cut has no effect on the grade achieved in these areas.
Again, this is where a good diamond education is critical. Understanding what makes a great looking diamond is complex. Valuing some quality elements at the expense of others is not always wise. Size will not necessarily give you a great looking diamond. A big, dull looking diamond is not what most people want!
The best cut diamonds reflect light back to the eye evenly when looking through the top of the diamond in the “face up” position. It is the same position as the diamond will be when it is set into a ring mount. When a diamond is well cut, light enters through the table and travels to the pavilion where it reflects from one side of the diamond to the other. It intensifies in the mirror-like facets before reflecting back out of the diamond through the table and into the observer’s eye. The brightness of a stone has a profound effect on how it appears to the naked eye and is referred to as “brilliance”.
Polish is defined as any imperfection on the surface of the stone after the final polish by the diamond cutter. It does not affect clarity.
The table is the largest and topmost facet on the diamond’s crown. The table percentage is the value which represents how the diameter of the table facet compares to the diameter of the entire diamond. So, for example, a diamond with a 53% table has a table which is 53% as wide as the diamond’s outline.
For a round diamond, gemologists calculate table percentage by dividing the diameter of the table, which is measured in millimetres, by the average girdle diameter.
For a fancy shape diamond, table percentage is calculated by dividing the width of the table, at the widest part of the diamond, by the millimetre width of the entire stone.
The Table measurements are subtleties which vary ever so slightly. They should not become a preoccupation in diamond selection. Again, diamond education is critical here. Often people think (because of something that they have read or been told), that a fixed table percentage is a “must have”. This should not take precedence over the many other factors that really impact on the look of the diamond. The technical aspects of a diamond, whilst important, should not be the sole determining factor in your decision making.
The Pavilion is the part of the diamond that lays just below the girdle. It is easy to see why people often neglect to consider its contribution to a diamond’s beauty. When a diamond is set, typically only the crown stands out prominently, and the girdle and pavilion are hidden beneath claws or bezels. They seem to serve only as the base, providing a way to seat the diamond in the mount.
However, it is this hidden part of the diamond that is the key to brilliance. The secret is in the pavilion angles, which, in a round diamond, should typically be between 40.5 and 41.5 degrees. Light reflected back to the eye from the pavilion differs from point to point within any given diamond. This is responsible for the diamond’s brilliance. Fancy shapes such as heart or princess cuts may require deeper pavilions than round diamonds in order to achieve the same amount of brilliance.
Diamond Education is Essential If You Want to Buy the Best Diamond That You Can:
No two diamonds are the same. The size, shape, colour and location of any inclusion are all factors determining which clarity grade a stone falls into. Often there is not a distinct difference between diamonds at the upper end of one grade and the lower-end of the grade above. So a high-end SI1 may be as good, if not better than a low end VS2. This is where good diamond education is critical, as factors like this affect cost.
When these diamonds are valued after being set into jewellery, it can be difficult to tell what grade the diamond may be. This even applies to highly trained gemologists and valuers. This can be due to reflections of the metal surrounding the stone. A diamond could look slightly more yellow if set in a yellow gold setting. An inclusion may be hidden under a claw or part of the metal bezel rim around the stone. A jewellery valuer can only value what they can see. If something is obscured from view by the ring mount, it will not form part of their assessment. As a result, a diamond may be given a greater or lesser value than it actually merits.
As a result, comparing diamonds in ready made rings is difficult. This is because you cannot see all aspects of the diamond once it has been set into a ring.
Even buying a certified diamond of D colour and VVS clarity does not guarantee a good appearance and play of light within the stone. If the diamond has poor lustre, it will not look good. This is regardless of its 4 C’s grade. If the cut is poor, a lower grade stone with a better cut will often look better. Differences between individual stones can be explained fully when purchasing a diamond from Ellissi, diamond education being a big part of what we do.
Grading of diamonds requires great expertise. Understanding the specific features of the diamond that have given rise to its grading report is very complex. To the untrained eye, stones which may be three or four grades apart may not appear to differ. Getting a diamond education from Ellissi can help to make the process easier.
A quality diamond does not just mean a big stone. Size is not everything. This is one of the main reasons new diamond purchasers find shopping and comparing jewellery prices difficult. Diamond education is a really important part of the process, as it will help you to understand what it is that you are buying.
The solution is to buy from someone you trust who has a direct interest in the integrity of their business. Someone who has extensive years of experience in the jewellery trade, who makes it a part of what they do to give you a diamond education in the process. Sales staff in retail shops are all too often under-trained, working in casual positions, trying to sell ready made stock they know little or nothing about.
We always recommend that you learn as much as you can. A good diamond education will help you to buy the best-looking diamond you can afford. After all, you will be wearing your engagement ring almost every day. You should be happy with what you see!
At Ellissi, we custom make all our rings. The ring is tailor made by us, to the design you want and to suit the diamond you choose.
If you would like to make an appointment for a great diamond education, please don’t hesitate to contact us.