The Diamond Basics (The 4 C's)

I’m sure you’ve heard of the 4Cs before: Colour, Clarity, Cut and Carat Weight. These four qualities/characteristics (are how diamonds are graded in order to be compared and evaluated in gemmological terms) allow diamonds to be compared and evaluated then graded in gemmological terms.

But what does this mean to you? We want to provide you with a practical view and understanding of what and how the 4Cs really correlate in getting you the best diamond for your engagement ring. We also want you to note that a diamond certificate doesn’t tell you the whole story. These numbers and letters alone can’t describe a diamond’s mysterious and captivating beauty. We reject 30% of the certificates we see based on misgrading.

To get the most beautiful stone, we recommend the 4Cs be prioritized in the following order: cut, colour, clarity, carat weight.

We will provide information primarily applicable to round diamonds, as all other shapes are designated as fancy shape (princess, radiant, oval, emerald, pear, marquise, cushion, asscher, heart). While colour, clarity and carat weight will remain consistent, each fancy cut varies so wildly we strongly recommend comparing several stones in person.


Most people believe that cut solely deals with the shape of the stone. That’s incorrect. Cut is a very tricky subject that is often over-simplified when presented to the client, even on the best certificates. This over-simplification obscures the differences in how each stone is seen by the human eye (also referred to as ‘face-up’). When we use the term, ‘cut’, we’re referring to the stone’s proportion, faceting and polish, not its shape.

The cut affects the diamond’s brilliance, fire and scintillation. Everything about a diamond is determined by nature. The stone’s ultimate beauty is a direct result of a master cutter’s work. A polished diamond’s elegance lies in its complex relationship with light: how light strikes its surface, how much light enters the diamond and how and in what form the light returns to your eye.

An excellent cut is essential to a diamond's presence, because even a diamond with outstanding colour and clarity will not display the brilliance that diamonds are famous for if its components don't interact with light as they should.  Of all the characteristics, the cut is most important.

The best round diamond you can buy is referred to as an Ideal cut. It gets its name from the ideal/perfect proportions and angles and has excellent symmetry and polish ratings. It is among the rarest of cuts and is perfectly proportioned to refract light, in the best possible way, producing a fire and brilliance up through to the table and crown back to the human eye.


Many people think of gem quality diamonds as colourless, truly colourless diamonds are actually very rare. When choosing a diamond, it is generally preferred to choose one with the least amount of colour possible.

Albeit simple in gemmological terms, determining the colour heavily relies on alphabetical ranges within the colour scale (colourless, near colourless, faint, very light, light). Within the ‘colourless’ section of the scale you are looking at three different hues (D, E and F), from which the price can vary significantly.

Think of colour as a clear glass of water. Left alone it is considered to be totally colorless, which gemmologists will call ‘D’ colour. If you add a splash of apple juice, the change in color, while not visible to the untrained eye, can be detected by a trained gemmologist using the right instruments. Consider every additional splash of apple juice a drop in the alphabetical colour grade. We strongly recommend not going below ‘G’ colour as the yellowness becomes visible to the naked eye at ‘H’ colour.

It should be noted that diamonds also come in a variety of fancy/vivid colours (from reds to blues to yellows to blacks) in which this scale does not apply.


Fluorescence is rather simple. Either a diamond has fluorescence, or it does not. None is the best in our book! Depending on the strength of a diamond’s fluorescence, it may greatly impoverish the colour of the stone, making it look fuzzy, milky or cloudy. It can be considered the most underrated segment on a gemmological certificate and is usually overlooked by consumers. (Don’t be fooled by thinking that a stone with fluorescence will counter balance a diamond with a lower colour grade – you’ll just end up with a foggy yellowish stone.)


Few things in nature are absolutely perfect. Diamonds are no exception. Diamonds can have internal features called inclusions, and surface irregularities called blemishes. Together, they’re called clarity characteristics. Clarity is the relative absence of inclusions and blemishes. It refers to how clear or clean the diamond is. As with colour, the clarity of a specific diamond falls within a specific range.

Most people want to avoid seeing any inclusions or blemishes, but are okay should the diamond contain some visible ones only seen under the power of a microscope. From a practical and budget conscious point of view, we’ll often recommend going as far down the clarity scale as you’re visually comfortable, where you can’t find an inclusion or blemish with a naked eye. This important distinction is referred to as ‘eye clean’.

Think back to that glass of water, at any colour level you want. Now add a couple grains of salt or pepper and call them inclusions. Just as in a diamond, some inclusions will be white or so small you could have dozens and they would be invisible to the eye, while, in another stone, just one small carefully placed black bit is easily seen. Consider every additional few grains of salt/pepper you add to be a drop on the clarity scale. We strongly recommend not going below an eye-clean SI1, again, it is something that needs to be seen and compared in person.


The last C, carat weight, is likely the easiest to quantify, but is extremely reliant on the cut. You’ve probably heard that she wants at least a certain sized carat stone; budget permitting. It’s really a simple concept: the larger the diamond, the more rare it is and the more expensive it will be. While it may be the easiest of the Cs to pin down, the important difference between size and weight will play the largest component of this final step in choosing a diamond.

One metric carat is equivalent to 1/5 of a gram. One carat is usually divided into 100 ‘points’. A 0.50 carat diamond is the same as a 50-points or ½ carat diamond.

Unfortunately, the terms size and weight are often used interchangeably when describing diamonds. This is just as grave a mistake as over-simplifying cut for shape. Please visit our ‘Size versus Weight’ section for further details to see how a diamond can be cut to look larger or weigh more than it actually does, in both instances forfeiting/diminishing its quality and overall integrity.

Picking the ‘right’ carat weight has no correct answer. It is completely subjective to your budget. We’re sure you’ve heard the old adage that you’re supposed to spend at least three month’s salary on an engagement ring. While this often is not an affordable or achievable standard to adhere to, and since carat weight influences cost quite a bit, we recommend you select a slightly smaller stone that is of better quality (the other 3Cs), than something that lacks life and brilliance, but is big and showy.