The Four C’s of Diamond Quality

Perhaps you’ve heard of the “Four C’s” of diamond quality. Each and every unique diamond in the world has its own defining characteristics, and understanding each of them will help […]

Perhaps you’ve heard of the “Four C’s” of diamond quality. Each and every unique diamond in the world has its own defining characteristics, and understanding each of them will help you make an informed decision when you come into a Spence Diamonds showroom.


Nothing is more important to the brilliance and sparkle of a diamond than its cut, as it is responsible for around 40% of a diamond’s price. A well cut diamond will reflect light from one facet to another and back through the top, creating a dramatic sparkling effect that only a diamond can emit. Only the most skilled diamond cutters can shape a diamond with exacting precision, to release its full brilliance, taking into account such factors as proportions, finish, and of course symmetry.


When examining a diamond, be sure to view it “loose” (unmounted) under a neutral light source, to get the best view of its colour. In the “normal colour” range, the colour of a diamond is rated on a scale that goes from D to Z, with D being the whitest diamond available, and Z being a tinted, light yellow colour. For most jewelry, a colour grade from G to J is usually best.

Why “D to Z?” Before this rating system was invented, diamond professionals used many other symbols (including liberal uses of “A” and “AA”) to rate colour, so the creators of the new system started at D, to avoid any confusion with the outdated ratings systems.

There are also various coloured diamond choices available today, but when you are looking specifically at a white diamond, you should understand how this scale works, and where your diamond of choice is rated on the spectrum. Also, the mounting of a diamond can impact its appearance. A more yellowish diamond will appear whiter next to a gold setting, whereas a white gold setting will make the diamond look less pure if you compare the two side-by-side.


The clarity of a diamond refers to the number and nature of inclusions or blemishes that are visible when you view it under a microscope. Some diamond professionals refer to clarity as “purity” or “quality,” but neither of those start with “C,” so we’ll stick with clarity.

A blemish is an imperfection on the surface of a diamond, and an inclusion is a small spot contained within it. Diamonds with little or no imperfections such as these are rarer, and much more valuable. Five factors determine a diamond’s clarity: the size, number, position, nature and “relief” of the inclusions. Relief describes the level of visibility of these imperfections. The clarity scale of a diamond is the easiest to understand: It varies from Flawless, to Internally Flawless, and from there goes to VVS, VS, SI and I. These are easy to understand and remember, because they stand for: Very Very Slightly included, Very Slightly included, Slightly Included, and Included. Each of these designations has varying levels as well, but getting a handle on these will help you understand the importance of clarity in a diamond’s grading.

An “I” rated diamond will have inclusions that are visible to the naked eye, whereas even a skilled diamond expert would need a microscope to see the inclusions in an “SI” diamond. Because of this, diamonds rated “SI” usually represent the best value for your investment.

Important Note: Skilled jewelry makers often mount a diamond so as to mask an inclusion from sight, helping it appear more flawless. Before buying a diamond, be sure to examine it loose under a microscope to get a better idea of its clarity.


The last and most obvious characteristic that a diamond is measured by is its Carat (abbreviated “ct.”). A carat is a measure of weight, and it takes 142 of them to make an ounce.

Interesting bits of trivia:
You can mail 142 one-carat diamonds with just a single postage stamp (Not that you would want to)!
The majority of diamonds used in jewelry weigh less than one carat.

Obviously, a diamond’s carat weight can have a big effect on its value. When written, carat weights are expressed as decimal numbers: 1.00 ct., 0.48 ct., 1.57 cts., and so on. In a piece which has more than one diamond, often times you will see the total carat weight of the diamonds shown.

At Spence Diamonds, each and every diamond comes with an official Diamond Certificate, which will give you a detailed blueprint of your diamond. Now that you understand the “Four C’s” of diamond grading, you’ll have a better understanding of these certificates, which give you detailed info on all of the factors discussed above, including a “plotting” that shows the exact location of inclusions and blemishes.

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