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Even the most novice of diamond buyers have likely heard of the four C’s. It’s the basics of diamond education and this simple mnemonic effectively encompasses the most crucial factors to consider when buying a diamond. Knowing them makes it easier to remember the all-important steps towards diamond success.

Aside from diamond cut–which is a quality factor that cannot be compromised–the four C’s offer flexibility to buyers, allowing them to prioritize those features which they feel are most important, and find a suitable balance of budget and beauty on those that are less impactful. With such a multitude of combinations in diamond quality, there is truly a diamond out there for everyone, and getting to grips with the Four C’s will empower you to make the best choices on your diamond journey.  

What Are The 4 C’s?

Anyone unsure on the 4 C’s or in need of a refresher will benefit from this quick review: 

“The 4 C’s are a mantra for diamond buyers that help to assess individual diamonds at a glance and avoid overwhelm in the face of all that sparkle. Cut, color, clarity, and carat come together to create an ultimate diamond checklist to assist in milestone moments and more whimsical purchases.”

More formally, the 4 C’s were introduced in the early 20th century by the Gemological Institute of America (GIA) as a method of standardization. This system helps both consumer and industry to evaluate diamond value and quality to create transparency and simplicity. 

Each C is important in its own right as they each dictate quality, either native to the stone or to the craftsmanship that helped to curate its natural form into something saleable. 

Which of The 4 C’s is Most Important?

Before evening learning about the 4 C’s many eager buyers are keen to learn which is most important. Unfortunately, the answer isn’t so simple. The 4 C’s are combined for good reason as they all play a role in overall diamond quality. 

Many may be tempted to say diamond cut is most important as it has the most influence on brilliance, fire, and overall appearance. However, the more materialistic amongst us may choose carat weight for its status symbol perks and ability to turn heads while some may swoon over a particular color or rightly crave clarity (especially if they’re a perfectionist). 

The more you know about diamonds, the easier it is to understand your priorities. You’ll start to understand how the 4 C’s blend and balance, what a good buy is and what it isn’t and exactly what to hone in on when you’re browsing.  

Diamond Cut

When diamonds are pulled from the earth in their ‘rough’ state, it seems unimaginable that they will be transformed into the bright and brilliant beauties that grace our jewelry. The cut refers to the proportions of the facets and is the aspect of diamond beauty that is controlled by man.

For brilliant cuts, the goal is to create numerous small facets that behave like mirrors, successfully bouncing light into the diamond and back to the eye of the viewer. A good cut will deliver the perfect balance of fire, brilliance and scintillation. A poor cut will result in light leakage and a dull, lackluster diamond.

For step cuts such as Emerald and Asscher, the aim is not sparkle but instead long, linear facets and wide tables that create an alluring ‘hall of mirrors’ effect that showcases a diamond’s perfect color and clarity. It is for this reason that step cuts require higher clarity and color grades than brilliant cuts.

Though often used interchangeably, diamond cut and diamond shape are two very different things. The shape refers to the outline of the diamond (i.e. heart shape, round shape) whilst the cut is specific to angles, proportions and facets of the diamond.

The above image shows a sample GIA dossier, including the diamond measurements. 

You will find lists of ‘ideal’ proportions for diamond cut, with small variance between them, and these can be helpful for narrowing down your search. 

However, the modern buyer will be pleased to know the technology is here to help. The best diamond vendors will offer advanced diamond imaging and performance reports. ASET, Hearts and Arrows, Idealscope and Sarine technologies can all give you tangible data in a user-friendly format that tells you exactly how the diamond is handling light. If you don’t have a head for numbers and find yourself befuddled by crown angles and pavilions, these images will prove invaluable to your search. Remember; light return equals sparkle.

Take a closer look at diamond cuts in this guide.

How To Evaluate Diamond Cut

Diamond cut gives diamonds that “wow” factor and as a result, often ends up as the “non-negotiable C” for many buyers. We all organically evaluate diamond cut as we stare in awe at a selected diamond in motion, either in store or on a 360 video. The better the diamond hits the light, the better the cut. 

However, we can more closely analyze the cut by checking its symmetry from a frontal position and using a magnifying loupe to scan for incorrect faceting or any other errors compromising the cut. A professional jeweler or gemologist can assist you in this process.


When it comes to the color of a diamond, colorless diamonds–also referred to as white diamonds–are the most popular for engagement rings and other fine jewelry. The presence of nitrogen, which becomes present during the diamond’s formation in the earth, causes diamonds to take on a yellow tone which is undesirable, so those which are colorless are truly special.

The scales tip when stones become intensely colored and are classified as ‘fancy colored diamonds’; these brightly colored stones are graded separately to colorless diamonds, yet they all appear in the GIA color scale below. 

It’s important to note that personal preference also comes into play when referencing diamond color. The industry grading certainly influences opinion but if you’re magnetized to a specific color or stone, perhaps it’s worth evaluating the other C’s on this list and thinking less about color.

The GIA scale above, and the formal rules around color, dictate price. Diamonds within the colorless category (D-F) command the highest prices due to their rarity, yet diamonds in the near colorless bracket (G-I) are usually indecipherable from the higher grades. My complete guide to diamond color will explain how to get the best trade off between a bright white diamond and a reasonable spend.

How to Evaluate Diamond Color

Of course, my in-depth guide will equip you to assess color as on an expert scale, however, some simple rules to follow include comparing against a master set of diamonds to match color, viewing the diamond under controlled lighting to identify true color and using a color graded chart if a master set isn’t available. 

You can also consult with a diamond expert and shop with highly-reviewed jewelers that you trust to do most of the hard work for you. These experts will assess diamond color, disclose this in individual product descriptions and show each diamond in its truest state using diamond technology and controlled lighting. 


Diamond clarity refers to the internal (inclusions) and external (blemishes) characteristics of a diamond. Most inclusions occur naturally as a diamond forms in the earth, but some are created during the polishing process or during enhancement. 

A natural reminder of a diamond's magnificent journey from earth to hand, all diamonds will contain inclusions to some degree, in many cases they can impede light return, diminish sparkle and even compromise the durability of a diamond. So, a diamond with as few blemishes or inclusions as possible is desired but is rarely possible. 

Clarity is one of the more complex areas of diamond quality grading. Diamonds are graded on the amount, size, relief, positioning and type of inclusion or blemish. Highly skilled graders must reach the same conclusion before a grade can be determined, eventually meeting one of the GIA categories above.

How to Evaluate Diamond Clarity

Despite being an intricate feature of diamond grading, for buyers the rules for selecting a diamond clarity are much more straightforward. 

Finding a diamond that is eye-clean is the name of the game. Eye-clean diamonds (which have no visible inclusions to the naked eye) can be found at an SI1 grade and above. The higher grades are much rarer and thus more expensive, but providing a diamond is eye-clean and has no inclusions that compromise the structure of a diamond, it is possible to maintain a reasonable spend on diamond clarity.

So, how can you determine if a diamond is eye-clean? The easiest conditions to check are under direct light. There are clarity charts you can refer to but for the average consumer, a combination of light and a keen eye should be enough to pick up on any major imperfections. 


Carat refers to the weight of the diamond. A standard carat is 200 milligrams, and each carat is subdivided into 100 points. For example, you may see a half carat diamond expressed as 0.50ct or 50 points. Carat is the only factor that can be precisely and objectively measured.

Buyers are, naturally, more concerned with the size of a diamond. While carat weight can tell you a little (a 1 carat diamond is obviously smaller than a 2-carat diamond), it is actually more complex than this. 

There is no average ‘size’ for a one carat diamond as the cut and diamond shape will also impact how big the diamond appears. This is why choosing a fantastic cut is so important as it will make your diamond look bigger!

Finding a gem quality diamond at the heavier carat weights is much harder, so the price increases not only with the weight but with the rarity and desirability.

Bigger or brighter? Find out which carat weight is best for you in this article.

How to Evaluate Carat 

As a truly objective measure, “evaluating” carats is easy. Jewelers will be explicit in communicating carat value after having already weighed the diamond in question and/or used a diamond gauge to estimate size. 

Carat is more of a consideration which can work in tandem with your other diamond knowledge. How does carat, for example, work alongside cut to form appearance? Most importantly, all in all, which C is most important to you? Carat may be just a small portion of what you’re looking for.

Beyond The Four C’s – Being Smart About Diamond Buying

The four C’s truly are the cornerstones of diamond buying. So much so, I have created individual pages to explain each of the four Cs in detail should you wish to find out more, be it about cut, clarity, color or carat.

Yet, the truth is, there is a never ending world of diamond education that can make you a more efficient and responsible buyer—and most importantly, help you to enjoy and get even more out of the exciting diamond buying process. From understanding diamond certifications to knowing the difference between lab-created and natural diamonds, every topic is worth exploring to some degree. 

Some considerations are purely personal also. Which shape do you feel drawn to and is there a specific setting you’ve got your eye on? For lifelong purchases, the search to find exactly what you have in mind is half the fun to know you’ve found the perfect stone to settle on. 

Finally, the diamond provider makes a big difference in the overall experiences. I’ve reviewed countless jewelers over the years to form the ultimate library of diamond reviews. My comparisons have helped me to make well-founded recommendations and signpost those in search of quality diamonds to suppliers such as Whiteflash for superior quality, Blue Nile for never-ending choice and Leibish and Co for those rare and sought-after colored diamonds. Between these three trustworthy jewelers, your perfect diamond is out there.