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The 4 C’s of Diamond Valuation - Royal Coster Diamonds

The 4 C’s of Diamond Valuation

What is a diamond?

A diamond is the hardest natural material. It is formed deep inside the earth. Under a high temperature and a high pressure, carbon atoms are pressed together. The atoms bond together and become a crystal. With (volcano) eruptions or earthquakes, the diamonds come to the surface where diamond workers find them. However, when the workers find diamonds, they look nothing like the ones you see in the jeweler's window. It’s easy to mistake a rough diamond for a worthless pebble. diamond mine explosion

Which diamonds are valuable?

Many diamonds that are found, are of bad quality. About 95% of the natural diamonds are unsuitable for jewelry. We only use them for industrial purposes, such as certain equipment. But we also use them to polish the diamonds that do have good quality. The remaining 5% is of good quality. These are the stones that eventually end up in jewelry. But its values isn’t decided yet.

When gets a diamond’s value determined?

First, the diamond is polished by a (professional) diamond polisher. When he or she sees the rough diamond, he or she has a general idea of the diamond’s potential. They make a rough estimation of how the diamond will look after it is polished. He has an idea about the probable carat, color, clarity and cut. However, the diamond’s value is still not decided. When the polisher finished the diamond, it’s sent to an (independent) certification authority. This authority examines the diamond up close. They measure and weigh the diamond. They examine its color exactly to determine where it falls on the diamond color scale. But they also investigate the inclusions with a very detailed microscope. Finally, they measure the quality of the craftsmanship. Usually, there is more than one person who examines the diamond. It gets looked at by multiple people to minimalize error. After that, the authority determines the final value of the diamond. Now, it is up for sale and can be placed in jewelry. But how do the so-called 4 C’s determine a diamond’s value? What to the authorities look for? We’ll tell you. diamond loupe and brilliant


The first one of the 4 C’s is Carat. Carat is the standard unit of weight for diamonds. There is a difference between Carat with a C and Karat with a K. Karat with a K is the percentage of gold in a mix. Carat with a C is the diamond weight. Carat takes its name from the carob seed. These small seeds had a uniform weight of 0.2 grams. That’s why early diamond traders used them as counterweights in their balance scales. In the modern metric, one carat still equals 0.2 grams. However, most diamonds sold are under one carat. That’s why we have a point system. 100 points is equal to 1 carat , 50 a ½ carat , 25 a ¼ carat and so forth. Generally, we can say: the bigger the carat, the more expensive the diamond. But the value also depends on the other C’s. man measuring diamond mm to carat


The second C, stands for Color. In the category of white diamonds, rule of thumb is: less color equals a higher value. As the diamond becomes more yellowish, the value drops. Sometimes we can’t see the difference in color with the naked eye. We use ‘master stones’ to see it. Diamond comes in many colors due to errors in crystallization and carbon. For example: brown and yellow diamonds are very common. diamond color scale from Royal Coster Diamonds However, there are also diamonds with a specific color. We call these Fancy Colored diamonds. Fancy colored diamonds are created by slight quirks of nature. Every colored diamond has its own story. For example, when a bit of boron slips into the carbon while it is becoming a diamond. In that case the diamond will not become white, but becomes blue instead. A bit of nitrogen makes a diamond yellow. Natural Fancies are extremely rare. There have been many notable colored diamonds throughout our history. One of the most famous ones is the Hope Diamond.


The Clarity of a diamond tells us something about its purity. The 4 C’s International grading system was created in the 1940s. Before that, a diamond’s purity was basically “without flaw” or “with flaw(s)”. We now know there are various degrees of diamond clarity. There are many different kind of inclusions. The type and amount of inclusions determine the diamond's clarity grade. This clarity is based on what we can see with a 10x magnifying loupe. That is where the term ‘loupe clean’ comes from flawless and pure. Some inclusions such as SI2 up to pique are visible to the naked eye. But other inclusions are only visible with a loupe. clarity grading scale diamond from GIA Clarity scale of the GIA (, in Europe we use the word Pique instead of Included.


The last but not least C stands for cut. This is the way the diamond is polished. It is the only one that is influenced by humans. The first ones are made by nature, the 4th one by us. Diamond cuts can be traced back to the middle ages. The first "improvements" on nature's design involved a simple polishing of the natural facets. This was called the point cut and dates from the mid-14th century; by 15th century, the point cut began to be improved upon. Sawing off one half off the diamond would create the table cut. By the 17th century the first brilliant cut in simple form was fashioned. ideal cut for the brilliant diamond

Quality of the cut

This is the historical evolution of the modern brilliant, facets added to the stone in just the order they were developed through the centuries and under the hands of the diamond cutter. The skills of the polisher plays a crucial role in this. It is why two diamonds with exact the same specifications can be very different in look and price. Up to 40% in some cases. The sizes need to be polished perfectly to get the perfect brilliance. Not too fat, not too skinny, but perfect. It can happen that two diamonds have the same specifications but because of the way it is cut, one sparkles more than the other. It seems alive. We call this fire or sparkle. ideal cut fine cut shallow and narrow A diamond needs to be polished perfectly: not too fat, not too skinny, but perfect

Different diamond cuts

And then there is a different kind of diamond cut. Even though the C for cut refers to the quality of the shape, a diamond can also get cut in any shape imaginable. There are round cuts such as the brilliant, the Royal 201 and the oval cut. But also rectangular cuts such as the princess cut and the radiant cut. And of course, there are many more. A great diamond polisher can create any diamond cut imaginable. But for the value it is also important to make the ratio perfect: not too fat, not too skinny.

What determines a diamond’s value?

Now you know the 4 C’s of diamond valuation. These four: the carat, color, clarity and cut determine a diamond’s value. To recap this really quickly:
  • Carat: a higher carat makes a diamond more valuable.
  • Color: the whiter the diamond the more valuable it is. However, fancy colored diamonds are even worth more than white diamonds.
  • Clarity: diamonds with no or little inclusions are more valuable than stones with inclusions.
  • Cut: if the polisher cut the diamond well, the diamond has a higher value.
If you want to get an amazing diamond, you have to keep the 4 C’s in mind. If you want to learn more about the 4 C’s, book our Royal Experience. This is an extensive tour about the history of diamonds and how to evaluate them. You also get to see and experience the difference between all sorts of diamonds. If you like to take a step further, you can also book a Diamond Masterclass. This is a 4-hour Masterclass, given by our master polishers. You go home with your own polished diamond and a certificate of completion.
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