Decoding the Lab Diamond 4Cs: A Buyer’s Guide to Finding the Perfect Lab Diamond

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The secret to finding the perfect lab diamond and the best possible price is understanding the lab diamond 4Cs. So read our intro to the lab-created diamond 4Cs and learn how to save money and get a much better diamond (while being better for the environment and society!)

We’ll teach you what you need to know before buying a lab-grown diamond in our easy guide to the lab-grown diamond 4Cs. Keep reading and start saving on your next lab diamond with our buyer’s guide to the lab diamond 4Cs.

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The history of lab diamond grading and the lab diamond 4Cs

In the world of lab-grown diamonds and mined diamonds, understanding the 4Cs—carat, cut, clarity, and color—is crucial. The concept of diamond grading through these four characteristics was introduced by the Gemological Institute of America (GIA) in the mid-20th century.

The evolution of diamond grading standards

Prior to the introduction of this system, there were no standardized methods for assessing a diamond’s value. This lack of consistency often led to confusion among buyers and sellers. When GIA introduced its diamond grading report, it revolutionized how both mined diamonds and lab-grown ones are evaluated today.

Most competition diamond grading institutes have since adopted or adjusted the diamond 4C grading approach, and the diamond 4Cs have become the de facto mode of assessing diamond quality.

Do the 4Cs apply to lab-grown diamonds?

The diamond 4Cs – carat, cut, color, and clarity – are universal standards for assessing diamond quality, including those grown in labs. So the 4Cs apply to lab diamonds just as they do to mined diamonds.

Grading of lab-grown diamonds

As laboratory-grown diamonds have become more prevalent in recent years due to technological advancements, lab diamonds, too, have been subjected to this rigorous diamond 4C evaluation method.

However, until recently, GIA would not grade lab diamonds. In its absence, other diamond grading institutes, notably the International Gemological Institute, IGI, now the largest lab diamond grading institute, took over. Today, GIA, too, grades lab-grown diamonds the same way they grade mined diamonds.

Learn more about how lab-grown diamonds are graded and certified.

Understanding the lab diamond 4Cs

The evaluation of diamond quality, whether lab-grown or mined, hinges on four fundamental elements. These elements are collectively known as the Diamond 4Cs – carat weight, cut grade, color grade, and clarity grade.

As detailed above, the “Diamond 4Cs” is the globally recognized standard for evaluating diamond quality. They comprise the key features to look at when assessing and buying diamonds. They are the same for both mined and lab-grown diamonds because lab diamonds are every bit as real diamonds as any diamond excavated from the earth. Thus, the lab diamond 4Cs are:

  • Carat: The weight of the diamond
  • Cut: The quality grade of the diamond cut
  • Color: The color grade (or tint) of the stone
  • Clarity: The clarity grade (clearness) of the stone

The 4Cs are graded and certified by independent evaluators. GIA (Gemological Institute of America) is the most well-known grader who invented the diamond 4Cs, formally known as the International Diamond Grading System. Today, many reputable grading laboratories exist. However, the International Gemological Institute (IGI) is the leading laboratory for grading lab-grown diamonds, and you’ll often come across their grading certificates.

Each of the 4Cs is critical when evaluating a diamond. Understanding the significance of each will not only help you pick the perfect diamond but also save money. If you want to go through a step-by-step guide to finding the perfect diamonds, read our lab-grown diamond buying guide.

If you want to learn the basics of lab-grown diamonds, keep reading our intro to lab-grown diamonds.

The lab diamond 4Cs

The evaluation of diamond quality, whether lab-grown or mined, hinges on four fundamental elements. These elements are collectively known as the Diamond 4Cs – carat weight, cut grade, color grade, and clarity grade.


We’ll start our intro to the lab diamond 4Cs with diamond carats, the most well-known lab diamond 4Cs. The term’ carat’ about diamonds often leads people astray. Contrary to popular belief, carats refer not to size but to a gemstone’s weight. This is the diamond way of saying how heavy the stone is. So, in the realm of diamonds, carats refer to a unit that measures their weight rather than size.

1 diamond carat is equal to 0.007 ounces or 0.2 grams. About the weight of a paper clip.

The carat weight significantly affects how large a diamond appears and its price tag in the market – larger stones often demand higher prices due to their rarity, as we note in our detailed guide on understanding diamond carats.

So people often think of carats as the size of a stone, and the two are indeed correlated. But the lab diamond carat weight also depends on the cut of the diamond, for example, the size of the “surface” versus the “bottom.”

Lab diamond carat weight is the first of the lab diamond 4Cs.

But, when a diamond is set in jewelry, you only see the stone’s surface. You don’t see the depth of the diamond. The depth of the diamond is a critical feature since it determines how the diamond reflects light. And, importantly, light reflection is what really matters diamond-wise, particularly for brilliant-cut lab diamonds.

As a rule of thumb, carat is what you would look for when determining how big the diamond stone is. Just be aware that it doesn’t give you the complete picture. Carat weight is a function of the size of the uncut “raw” stone, how efficient the cutting process has been, and the shape of the diamond.

To learn more about lab-grown diamond carats and the importance of carats when you shop for diamonds, read our in-depth diamond carat guide.

Lab diamond carat buying tips

Many people aim for certain carat weights, say 0.5, 1.0, or 2.0. This is primarily a vanity decision that allows you to tell others you have a specific “size” diamond. Take advantage of this and get a stone just below these popular weights, for example, 0.96-0.99. The difference will not be noticeable, and you might save money or be able to upgrade the lab diamond cut grade.

Lab diamond cut

Diamond cut grade is the most critical factor when determining the quality of the stone, in particular when it comes to the “sparkle,” which makes diamonds so unique. The diamond cut should not be confused with diamond shapes. The shape determines whether the diamond is round, oval, or even heart-shaped.

The diamond cut is solely related to how well the diamond has been cut into whatever shape it should be. The most important aspect of the cut is how light is reflected.

An expertly cut diamond reflects light beautifully, creating a captivating effect that draws attention from every angle. In contrast, poorly-cut ones lack such allure despite having comparable attributes in other areas, including size, color, and clarity.

So even if you have a larger carat weight laboratory-grown diamond with exceptional clarity and high color grading but poor cutting, it won’t display the desired beauty or brilliance due to insufficient or unsuitable light return.

Diamond cuts are highly complex and constructed to reflect as much light as possible. This requires the stone to be cut at certain angles and that the depth-to-surface ratio, and other ratios, are just right. Not an easy task.

Diamond cut grade is the most important factor when determining the quality of a lab-grown diamond.

Before the diamond is cut, the stone is in its raw form. Like the final cut, the raw forms also differ. Particularly for mined diamonds, while the laboratory-creation process is more controlled, and the raw form tends to vary slightly less. How well the diamond cut turns out depends on the size and shape of the raw stone. Basically, what the diamond cutter has to work with.

Lab-grown diamond cut - Intro to Lab-Grown Diamonds

As the stone is cut to maximize brilliance, more and more raw diamond is discarded. This hurts the carat weight. The cutter might also try to cut around inclusions to improve diamond clarity, which impacts the weight or quality of the cut. There is, therefore, often a trade-off between cut grade, clarity, and weight. Often carat weight or clarity suffers to obtain the best possible diamond cut.

This explains why a high-grade cut is more expensive. It not only requires hours of highly skilled labor but also compromises the weight of the finished diamond. Since the cut is independent of how the diamond was created, the diamond cut and what you pay for it are exactly the same for mined and lab-grown diamonds. That’s why diamonds will always be costly and hold value even as prices fall.

The leading grading institutes differ slightly in their diamond-cut grading requirements, approach, and grade names. However, these are the most typical cut grades that you will also see lab diamond jewelers list on their websites:

  • Ideal or Excellent: This is the very best grade and the only one you should pick. GIA uses Excellent as the highest grade, while IGI uses Ideal.
  • Very Good: This grade is often used for pre-set lab diamond jewelry. Beware of the Very Good grade. It is, in fact, not very good. And, particularly if you are searching for a brilliant-cut lab diamond, you should not settle for Very Good.
  • Good: Is not good. Stay away from this cut grade, regardless of the diamond shape.
  • Poor: Is, in fact, very poor. Also, stay away from this lab diamond cut grade.

In summary, the cut grade is the most important of all lab diamonds 4Cs. And you should always pick the best possible grade.

Lab diamond cut buying tip

Always, always, always maximize the cut grade of the stone you’re buying. Instead, compromise on color, clarity, or, ideally, carat. We recommend that you don’t go below the excellent or ideal cut.

Learn more about the diamond cut in our in-depth article on lab-grown diamond cut.

Lab diamond color

The next of the lab diamond 4Cs is color. The name diamond color can be a bit misleading. It is actually the absence of color, or rather lack of tint, that matters. Naturally, as well as in the laboratory, the presence of gas (nitrogen) or structural imperfections can make the diamond appear tinted – typically yellow or brownish. This is the reason why not all diamonds are colorless – even if grown in a laboratory. In fact, most diamonds are not colorless.

Diamond colors are graded between D and Z, with D being truly colorless and Z being clearly yellow or brownish in color.

A, B and C diamond color grades were consciously not included to avoid confusion with other existing (and now deprecated) color grading systems.

The typical gemstone quality lab diamond color grade you’ll see at lab diamond jewelers are:

  • DEF: Colorless (expensive)
  • GHIJ: Near-colorless (best value)
  • K+: Probably too tinted

While some buyers prefer warmer tones, most opt for cooler hues on the colorless or near-colorless scale. However, subtle differences between consecutive grades are hardly noticeable, especially once set into jewelry. Only once you go below the recommended gemstone quality color grades (typically below K) can you see the color differences with the naked eye.

So what you need to know about diamond color grades is that from the colorless “D” down to “G” and “H” and under some circumstances all the way to the “K” grade, the color imperfections will be unnoticeable.

However, the price differences are noticeable. Between two adjacent colors (e.g., H->I), you likely cannot tell any difference. Colorless diamonds are extremely rare and, therefore, also costly. Unless money is no object, avoid them. Particularly colorless DEF-graded lab diamonds are usually not worth the much higher price tags (see our recommended grades below).

Further, the jewelry set that the stone will sit in also impacts color perception. For example, a gold or rose gold setting will emit some of its yellow colors and “pollute” the light reflected by the diamond. For this reason, you can compromise on color grade if the diamond will be near something colored.

What are fancy-colored diamonds?

Lab diamond color should not be confused with “fancy” colors. Naturally occurring fancy-colored diamonds are both very rare and very expensive. But not in the laboratory, where fancy-colored lab diamonds are easier to create. That’s why fancy-colored diamonds often are lab-grown.

The fancy color is not related to the transparency or light-emitting qualities but the actual color of the stone, for example, red, blue, or pink. To avoid (or maybe add) confusion, fancy colored diamonds have the color grade Z+ and a graded along a three-dimensional scale.

You can learn more in our guide to fancy-colored lab diamonds and guide to fancy-colored lab diamond engagement rings.

Lab diamond color buying tip

Since colorless diamonds are both extremely rare and expensive and since the difference between color grades is often not noticeable in a natural light setting, go for, at most, the G color grade. The DEF (colorless) is, in our opinion, overvalued. You will likely not subject your jewelry to a microscope inspection in a lab after you’ve purchased it anyway – and neither will anyone else.

For brilliant-cut lab diamonds they’ll often give off an immense sparkle that will outshine colored light (especially when you opt for the highest cut grade). With these, the GHI and sometimes J color grades present the best value, and we often recommend I when searching for brilliant-cut lab diamonds. And, if set in gold or rose gold, consider a J or K color-graded diamond. Spend your savings upgrading to a better diamond cut!

Some fancy-shaped diamonds, such as emerald-cut, will display more color, and for emerald-shaped lab diamonds, we recommend aiming for a slightly higher color grade.

If you are shopping for a fancy-colored lab diamond, you have your work cut out for you, but we’ll help you with our easy guide to diamond colors. Just note that color is king with fancy diamonds (not cut) and that you should exclusively buy from a seller who offers high-quality diamond images (like Ritani, James Allen, or Clean Origin).

Lab diamond clarity

The last of the lab diamond 4Cs is diamond clarity. While it could be confused with color imperfections, clarity is actually about tiny internal inclusions trapped in the stone or surface blemishes. They appear like tiny cracks (internal) or scratches (external). Both mined and lab-created diamonds have inclusions and blemishes. Even in the sterile laboratory environment, the growing process leads to imperfections, and flawless diamond clarity is, just like in nature, very rare. And rare equals expensive.

Diamonds are graded on a scale from flawless (F) to I3 (the worst). The grading is done by magnifying the diamond 10 times (in practice, often more) to inspect and determine the imperfections’ size, position, and severity. Certified grading laboratories carry out the process. Notably, these flaws are only seen under 10X magnification by a highly trained grader. Therefore, except for the lowest-graded diamonds (I1-3), most people cannot see any flaws.

The last of the lab diamond 4Cs is diamond clarity.

There are two problems with inclusions and blemishes. The first is that they detract from the cleanliness or look of the stone. However, as most flaws are impossible to see with the naked eye, this is less of a worry. Just stay clear of I-graded diamonds. Most gem-quality diamonds fall between the VVS and SI grades.

The other problem is that even tiny impurities you cannot see can harm the diamond’s ability to reflect light and, therefore, its brilliance. However, as was the case with the diamond color, the cut quality matters much more than the clarity when it comes to the sparkle of a diamond.

If you want to dig deeper into lab-grown diamond clarity, then read our in-depth guide to lab-grown diamond clarity.

Diamond clarity buying tips

Flawless diamonds are rare and are not worth the considerable premium. Unless you’re buying diamonds for investment purposes, which we don’t think you should anyway. The same often goes for the VVS1/2 grades, which are expensive.

If you buy a round brilliant or similar brilliant-type diamond, you will most likely be fine with a VS1 (better) or sometimes even a SI2, but you should study the HD diamond images closely.

Grading is not a perfect science and relies on the skill of the particular grader and laboratory, which introduces variance in grading. The most important thing to do when considering diamond clarity is to inspect it yourself to see if the diamond is “eye clean.” That is, check if you can see any imperfections under the 10-20X magnifications that the best lab diamond jewelers display on their websites. Make sure to take your time to inspect these HD images closely!

So, a good rule of thumb would be aiming somewhere around the VS1-VS2 range, where flaws aren’t usually discernible by the naked eye, thus providing an excellent value-for-money proposition compared to higher-grade options offering little additional visual appeal despite their steeper price tags. Consider SI1-2, but you need a little patience to find an eye-clean lab diamond at these lower grades.

We recommend buying at Clean Origin, Ritani, and James Allen since they allow you to carry out a proper inspection and offer unmatched support where you can ask for unbiased (and uncommissioned) guidance. Read our Clean Origin review, review of Ritani, and James Allen lab-grown diamond review.

What is the most important lab diamond C?

Choosing and prioritizing the lab diamond 4Cs comes down to personal preference and how you plan to use the diamond. But in most cases, you should prioritize diamond cut over everything else. Diamond color and clarity come next. The least important diamond characteristic is the carat weight. Any diamond with the highest-graded diamond cut will look better than a larger diamond with a poor cut. Diamonds are all about sparkle, which depends primarily on how well the diamond has been cut to reflect light.

Ultimately, it comes down to personal preference and how you will use the diamond. That said, we strongly recommend the following order of importance.

Our recommendation, again, depends on your use case and if the price matters. Since it probably does matter, use the below as a rough guide but make sure to learn the basics of lab-grown diamonds yourself.

  1. Diamond cut: Has by far the biggest impact on brilliance and, in turn, how big and impressive the diamond looks. The brilliance is the unique feature that makes diamonds special and is probably the reason you’re looking for one in the first place. So choose an excellent or ideal cut plan diamond. Unless you’re buying a fancy-colored diamond. In that case, color is king.
  2. Diamond color: You can safely downgrade to a G or H and even to an I or J with a brilliant cut when paired with a gold setting. However, the yellow tint should not be too noticeable or distract from the diamond’s beauty.
  3. Diamond clarity: A very close third, clarity can potentially negatively impact the stone’s ability to reflect light and, in turn, its brilliance. However, you’ll likely suffice with a diamond between VSI1 or SI2 and should rather compromise on clarity than cut.
  4. Diamond carat: Often the C that people care most about – but it really shouldn’t be. A large diamond with poor cut, color, and clarity will appear much smaller than a higher-grade but smaller stone. Consider a smaller but better cut-graded lab diamond and include diamonds just below the popular carat weights, where you may find a good lab diamond deal.
What are the best grades of lab-grown diamonds?

The highest grade for a lab-grown diamond would be one with an excellent or ideal cut, D color rating (colorless), flawless clarity, and high carat weight.

What is the best color for a lab-grown diamond?

Diamonds graded D through F on the GIA scale are considered top-tier as they’re virtually colorless. However, personal preference plays a significant role in choosing your ideal diamond hue.

Find the best deals on lab-grown diamonds

You can save even more than 60-80% on lab-grown diamonds compared to mined equivalents. How? Just follow our updated list of current deals and sales on lab-created diamonds and lab-diamond jewelry.

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Rolf Hartmann
Rolf Hartmann

Rolf Hartmann has decades of experience in the jewelry industry. He knows everything you need to know to find the perfect diamond. He's an expert in lab-grown diamonds and has followed the exciting development of lab diamonds from industrial usage to the incredible gemstone quality that lab-grown diamonds are today. Rolf guides you to find the right diamond at the best possible price and expertly and transparently reviews all lab-grown diamond sellers.

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