The Ultimate Guide to Diamond Ratings and the 4 Cs

What are the 4 C’s of diamonds? How do diamond ratings work? And what’s a GIA report, anyway? Read on for answers!

Getting engaged soon? Don’t worry: your search for that perfect diamond doesn’t have to stressful and confusing.

But how can you trust that you are buying a good quality diamond? What are the most important things to look for when buying a diamond?

The diamond buying process can be overwhelming, but fear not: GIA, the Gemological Institute of America, can help.

This independent non-profit organization protects you, the diamond purchaser, with unbiased scientific research, education and diamond grading.

They are the authority on diamond quality and can steer you in the right direction, giving you the confidence to avoid costly and potentially embarrassing mistakes.

About GIA

Founded in 1931, GIA developed the first – and now globally accepted — quality standards for judging diamonds. Those who deal in the world’s best diamonds relies on GIA to accurately assess the quality and characteristics of their stones.

The GIA standard is known as the 4Cs: Color, Clarity, Cut and Carat Weight.

GIA also developed the International Diamond Grading System, which is a scientific method for evaluating and describing diamond quality (or diamond ratings) using the 4Cs.

With a GIA Diamond Grading Report in hand, you can have confidence in what you are buying, because it is a scientific and unbiased blueprint of your diamond’s exact quality characteristics.

Diamond Ratings: What the 4Cs Measure

You don’t need a degree in gemology to buy a great diamond, but it can help to know a bit about the 4Cs.

Color

It is the absence of color that distinguishes the purest of white diamonds. The less color there is in the stone, the rarer it is. This is not to be confused with “fancy” colored diamonds which can come in a variety of hues; these rare colored diamonds are graded on a different scale.

However, in a white (colorless) diamond, the presence of color, like a yellow tint, lowers its value and the less color it has, the greater its market price, if everything else is the same.

Some diamonds develop with an inherent color which is part of their natural composition. This is caused by the trace elements present when the diamond is forming deep in the earth. It is extremely rare to find a diamond that is completely colorless.

GIA has developed an international industry standard scale for color which goes from D, the rarest and virtually colorless, to Z, which will have yellow or brown tones.

D: Totally colorless. The highest possible grade. Very rare and expensive.

E: Considered colorless but has traces of color which can only be detected by an expert. A high-quality diamond.

F: Still considered colorless, but an expert can detect color traces. A high-quality diamond, nevertheless.

G-H-I-J: Nearly colorless and a good value.

K-L-M: Faintly tinted, usually yellow.

N-O-P-Q-R: Lightly tinted in progressively darker shades of yellow or sometimes brown. Color can be seen with the naked eye.

S-T-U-V-W-X-Y-Z: Tinted, usually yellow or sometimes brown. Color is easy to see.

Clarity

The clarity of a diamond is based on how many “flaws” it has. Diamond experts call these natural irregularities “inclusions” and “blemishes” (not flaws).

These may have an impact on the value of a diamond but are often microscopic so do not necessarily affect its beauty.

Natural diamonds are formed from carbon exposed to tremendous heat and pressure deep in the earth. Diamond “flaws” are completely natural.

They can be tiny crystals, structural irregularities, or tiny cracks called “feathers” that can appear during the formation of the gem.

Flaws within the diamond itself are called “inclusions” and flaws on the outside are called “blemishes” and they are what make each gem unique.

Diamonds with the fewest inclusions or blemishes are obviously the rarest, most highly prized and therefore the most expensive.

It is the amount, the size, and the location of these inclusions and blemishes that will determine the clarity grade of your diamond. A diamond with few or no inclusions is considered rare.

The GIA Diamond Clarity Scale has 6 categories, some of which are divided, for a total of 11 specific grades:

• Flawless (FL) No inclusions and no blemishes visible under 10x magnification
• Internally Flawless (IF) No inclusions visible under 10x magnification, but might have a very small, insignificant blemish
• Very, Very Slightly Included (VVS₁ and VVS₂) Inclusions so slight they are difficult for a skilled grader to see under 10x magnification
• Very Slightly Included (VS₁ and VS₂) Inclusions can be seen with effort under 10x magnification, but are still minor
• Slightly Included (SI₁ and SI₂) Inclusions are noticeable under 10x magnification
• Included (I₁, I₂, and I₃) Inclusions are obvious under 10x magnification which may affect transparency and brilliance

So, what clarity grade should you choose?

Unless you have an unlimited budget and are going for a top-of-the-line gem, you shouldn’t go for Flawless. There are stunning diamonds with lower clarity grades.

See Also: How to Choose a Men’s Wedding Ring

Diamonds with VVS and VS grades look just as magnificent but are somewhat easier on your wallet. SI₁ and SI₂ diamonds will not have any visible inclusions that can be seen by the naked eye and they are more affordable still. These are what gemologists call “eye clean.”

Whatever your choice in terms of clarity, it is always possible to place more emphasis on one of the other Cs, if you determine that carat weight or cut is more important to you.

Clarity, in general, has the least impact on a diamond’s appearance and overall beauty, so it is worth remembering that even if you decide to choose a stone with a few inclusions, they will be totally invisible to all but the gemologist – and you will still have a stunning ring.

Cut

You’ll be surprised to learn that the most critical factor in determining the beauty of a diamond is considered by experts to be its cut quality and not its clarity.

The overall appeal, symmetry and value of a diamond are largely determined by the quality of its cut. Of all the diamond 4Cs, Cut is the most complex and technically difficult to assess.

The cut quality of a diamond (a jeweler might call it “make”) has a direct correlation to its value and appeal; an expert diamond cutter can bring out its inherent beauty with a masterful balance of symmetry, facets, proportion and polish.

When a diamond has been well cut, it is able to both reflect and refract light; understanding the way light moves is a critical part of the cutter’s art. Specific cuts and proportions have been developed by expert cutters over the centuries to make the most of each diamond.

Simply put, the better the cut quality, the more it will sparkle. An expertly cut smaller diamond may, in fact, be worth more than a bigger one. A diamond’s cut grade is based on its appearance and its design and craftsmanship.

3 Optical Attributes That Contribute to a Beautiful Diamond’s Appearance

The beauty of diamonds is a little more complex than people may think. Here are three lesser known attributing factors.

#1: Dispersion or Fire

This refers to the spectrum of colors that is reflected to the eye from the diamond, like the colors in a rainbow. When light enters the diamond, it is reflected around its interior, bouncing off its facets and then leaving through the crown of the gem.

Some beams of light separate and reach the eye in brilliant flashes of color. Fire is a highly-prized feature of a well-cut diamond.

#2: Brightness

This refers to how much white light exits out of the top of the diamond through the table, reflecting back to the eye. Many people call this brilliance, but that’s a more ambiguous term.

#3: Scintillation

The flashes of light and contrasting dark areas you see when a diamond or the light source is moved. It is a sparkling or glittering effect on the diamond’s surface which represents both reflection and refraction of light.

It’s the balance and optimizing of these three types of light reflection that make a true top-quality diamond. The best-cut diamonds have proportions that maximize their light dispersion, brightness and scintillation and so the grading scale for Cut is based on this very delicate equation.

The GIA Diamond Cut Scale


Excellent – Represents the top tier in diamond quality based on cut, polish and symmetry. These are outstanding stones with an even pattern of bright and dark areas.

Very Good – Represents those diamonds that are nearly in the top tier of diamond cut quality. Any small areas of darkness or dullness in the pattern are barely noticeable.

Good – Represents diamonds that are less sparkling. They have moderately-sized dull or dark areas in their pattern.

Fair – Represents a less desirable diamond cut quality. They have large areas of darkness or dullness.

Poor – Represents diamonds that are cut substantially too deep or too shallow, so they lose light out of the sides and bottom. They have a mediocre appearance.

Carat Weight

Carat is the term most often associated with the purchase of a diamond. However, did you know that a diamond’s carat measurement refers to its weight and not its size?

Size refers to its physical dimensions, like its diameter or width measurement.

The modern carat system actually started with the carob seed. Early gem traders used the small, uniform seeds as counterweights in their balance scales.

The carat is universally accepted as the same gram weight in every corner of the world.

A carat (not to be mistaken with the word karat, which describes the purity of gold) is a unit of weight specifically for diamonds and is equivalent to 200 milligrams.

Carat weight is commonly expressed in points or fractions and one carat is equal to 100 points, so each point is equivalent to 1/100^th of a carat (0.01).

Other types of gemstones are also measured in carats, but different gems of the same weight are not necessarily the same size because they have different densities.

Here Are Some Other Pointers about Carat Weight

First, carat is usually abbreviated as “ct” for a single stone. The letters “tcw” refer to “total carat weight,” or sometimes just “tw” for “total weight”, which is the combined diamond weight of a ring with multiple stones.

For instance, a halo ring, with smaller diamonds surrounding a larger central one, may be quoted in tcw because it has multiple diamonds.

If you are wondering whether size really does matter when buying a diamond, remember that larger diamonds are rarer and more in demand, so diamond prices tend rise in conjunction with carat weight.

A 1.00 ct stone will be more expensive than two 0.50 ct diamonds of the same quality. Double the weight of a diamond, generally speaking, and you more than double the cost.

As a rule of thumb, multiple smaller stones weighing as much as one larger stone will always cost less even though they weigh the same, which does not seem logical.

On the other hand, two diamonds of equal weight may have different pricing if their clarity and cut are not of equal quality.

Some weights are considered “magic sizes” – half carat, three-quarter carat, and one carat. Visually, there’s little difference between a 0.99 ct diamond and one that weighs a full carat.

The price differences between the two can be significant and the 0.99 ct diamond is considerably cheaper.

Which of the 4Cs Is the Most Important?

The answer will be based on your budget and your (or her!) personal preferences. If Carat weight is your number one priority, then go for the largest diamond you can afford, given that you’ll have to compromise on its Color, Clarity and Cut.

Similarly, if Clarity is most important to you, then the other 4Cs will necessarily have to take second place. Perhaps a balance of all 4Cs makes the most sense?

I recommend you sit down and list your priorities in terms of the 4Cs – but stick to your budget! You do not want to start out your married life by going into debt.

Get a GIA Report

Finally, I recommend you make sure to ask your jeweler or online retailer for a grading report from GIA before you purchase a diamond, so that you can be sure you understand exactly what you are buying.

You wouldn’t but a car without a history report from Carfax, right? It’s kind of the same thing with diamonds.

You can send your diamond directly to GIA who will grade and analyze it for you, or have your retailer send it on your behalf so they can manage the shipping and insurance.

Remember that GIA only analyzes unmounted diamonds so, if you can, have it sent to them before it is put into your chosen ring. If not, your jeweler will need to take it out of its setting before grading.

I make this recommendation because a GIA Diamond Grading Report is the only universally accepted, unbiased assessment of your diamond’s overall quality. It gives you a detailed analysis of Color, Clarity, Cut and Carat Weight.

Plus, you can also get a version of the report that has a diagram clearly showing the location of the diamond’s inclusions and blemishes.

All GIA reports contain security features – such as a hologram, security screen and microprint lines – that prevent them from being forged or duplicated. Your GIA report can also be used to identify a lost or stolen diamond, if you are unlucky enough to lose it.

Also, keep in mind that most appraisers and insurance companies rely on these kinds of reports as definitive proof of a diamond’s quality. So a GIA diamond ratings report is essential if you plan on insuring your engagement ring – which I recommend you do.

Getting engaged and buying a diamond is stressful enough, but if you have the backing of GIA’s unbiased, scientific team behind you, a lot of this stress can be lifted – and you’ll be confident in your purchase.

Further Reading: How to Buy the Perfect Engagement Ring