Diamond Buying and the 4 Cs, Part 4: Assessing Diamond Clarity


Summary
First-time buyers may find assessing diamond clarity challenging. Inclusions, tiny crystals and other features within gemstones, may be difficult to see and identify. Some inclusions may add interest or have no impact on value. Others may negatively affect not only a diamond’s optical performance but also its structural integrity.

In this fourth of a 4-part series of articles, we’ll introduce diamond buyers to our diamond clarity chart, which contains information on clarity terminology and explains how professionals grade clarity. We’ll also bring together all the Four Cs of gem grading — carat, color, cut, and clarity — and recommend combinations that work well.

Reading time: 10 min 43 sec
diamond with crystal inclusion - diamond clarity
Diamond with natural crystal inside. Photo by Giuliofranzinetti. Licensed under CC By-SA 4.0.
yellow diamond with inclusions - diamond clarity
2.93-ct yellow diamond with a few inclusions. South Africa. © Rob Lavinsky, www.iRocks.com. Used with permission.

What is Clarity?

Clarity covers all things in a stone that affect the free passage of light. Thus, gem graders consider transparency, inclusions, and surface blemishes when evaluating clarity. Many gemstones contain inclusions, including virtually all diamonds. However, some are so small they don’t impact grading.

Inclusions in diamonds include things like minerals, some in crystal shapes and others in long needle shapes, and twinning wisps that form inside a stone. Gem cutters usually try to cut a piece of diamond rough to create a stone as free of inclusions as possible. Typically, inclusions can’t be removed, though some treatments try to minimize their impact in faceted gems.

Generally, the freer from inclusions, the more valuable the diamond. Nevertheless, geologists love inclusions in diamonds, since they reveal a lot about the Earth’s formation. (The youngest diamond is 900 million years old). Some inclusions can be quite beautiful and interesting, too. Diamonds can contain gems such as garnet or diopside and, often, even mini diamond crystals. In some cases, diamonds contain diamond inclusions that contain diamond inclusions! They all fit, one inside the other, like a Russian matryoshka doll. Included diamonds can make fascinating pieces for mineral or gem collections.

Russian diamond - diamond clarity
Heavily included Russian diamond. Photo by James St. John. Licensed under CC By 2.0.

Inclusions can also help gemologists distinguish natural diamonds from synthetic diamonds or diamond imitations. Natural diamonds contain a much greater variety of minerals and inclusions than synthetics do. Furthermore, synthetic diamonds don’t contain natural crystal inclusions.

Diamond Clarity Chart and Grades

Professional gem graders use the following diamond clarity grades.

No Inclusions

  • F: Flawless:
  • IF: Internally Flawless

Minute Inclusions

  • VVS1: Very, very slightly included 1
  • VVS2: Very, very slightly included 2

Minor Inclusions

  • VS1: Very slightly included 1
  • VS2: Very slightly included 2

Noticeable Inclusions

  • SI1: Slightly Included 1
  • SI2: Slightly Included 2

Obvious Inclusions

  • I1: Included 1
  • I2: Included 2
  • I3: Included 3
diamond clarity chart
Diamond clarity chart and grades. Image by Open School of Gemology. Licensed under CC By 3.0.

Flawless

“Flawless” diamonds are flawless inside and out. At 10X magnification under a microscope, they have no visible blemishes or inclusions. (If a diamond has inclusions too small to see at this magnification, they have no effect on the clarity grade).

“Internally flawless” means that the stone has blemishes but no inclusions. Blemishes encompass things like scratches and nicks that exist only on the external diamond surface. Usually, they can be polished away and likely won’t affect the clarity grade too much. On the other hand, inclusions like crystals and feathers (cracks) exist inside the stone. These have much more impact on the clarity grade.

Incredibly rare, flawless and internally flawless stones account for just 2% of gem-grade diamonds. Thus, they command high prices, especially in large carat sizes.

You’ll find an enormous price difference between an F and an IF stone, like that between an IF and a VVS stone. As clarity grades go down, the price differences decrease exponentially.

Very Very Slightly Included

VVS stones have minute inclusions, so small they’re barely noticeable under 10X magnification. Most consumers likely can’t tell the difference between F, IF, and VVS diamonds.

Any stone in the VVS range still has extremely high clarity and will command a premium price.

VVS - diamond clarity
VVS clarity diamond. A tiny cleavage crack at the girdle (almost at 10 o’clock), penetrating into a crown main facet. Images by Open School of Gemology. Licensed under CC By 3.0.

Very Slightly Included

VS stones occupy the upper-middle range of diamond clarity grades. They have minor inclusions, which means they don’t interfere much with clarity, even though they’re larger or more numerous than those in VVS stones.

VS - diamond clarity
VS clarity diamond. A few small, light crystals in the crown. Images by Open School of Gemology. Licensed under CC By 3.0.
VS1 vs SI2 - diamond clarity
A comparison of VS1 and SI2 clarity. Photo by Diamka2014. Licensed under CC By-SA 3.0.

Slightly Included

Stones in the SI range drop into commercial-quality. (Think Costco or Walmart). The inclusions are noticeable at 10X magnification but most likely not with the naked eye. Still, an SI stone may appear cloudier and less brilliant, especially to someone familiar with fine jewelry.

SI - diamond clarity
SI clarity diamond. Light crack in pavilion facets seen through the crown. Images by Open School of Gemology. Licensed under CC By 3.0.

Included

Generally, buying I stones isn’t a good idea, even though they’re technically gem quality. I diamonds have inclusions obvious even to the naked eye. Furthermore, these inclusions may even affect the diamond’s durability or wearability, especially I3 stones.

I1 - diamond clarity
I1 clarity diamond. Crystal inclusion and crack under table. Images by Open School of Gemology. Licensed under CC By 3.0.
I2 - diamond clarity
I2 clarity diamond. Larger fracture crack under crown facets, dark inclusion under table. Images by Open School of Gemology. Licensed under CC By 3.0.
I3 - diamond clarity
I3 clarity diamond. Several distinct cracks. Images by Open School of Gemology. Licensed under CC By 3.0.

Clarity and Diamond Buying

Choosing whether to buy a Flawless or a Slightly Included diamond for your engagement ring can depend on the stone’s other quality factors. The larger the stone, the more visible the inclusions, simply because you’ll have more surface area to view. For stones much larger than one carat, look for a clarity grade of VS or higher. For stones one carat or smaller, VS or even SI grades are pretty standard. In small stones (those below half a carat), clarity doesn’t matter as much. Color grades will be more noticeable.

When buying a diamond, it’s essential to look closely at the stone. If you’re buying online, always review magnified video of the diamond to ensure that its imperfections do not impact its beauty.

Evaluating Inclusions and Their Impact on Diamond Clarity

Size

Diamond graders assign diamond grades by looking at stones under 10X magnification. When examining an inclusion, the most important consideration is size. Obviously, an enormous inclusion will have a much bigger impact on a stone’s visual appeal than a small inclusion.

Number

The quantity of inclusions also matters. Even tiny inclusions will make a diamond look unattractive if too numerous.

Location

Location also affects the visibility of any inclusions. The worst location is the table facet. Since the table acts like a window into the stone, inclusions will be most visible there.

tension cracks - diamond clarity
Crystal inclusion showing tension cracks, highly visible through the table. Photo by Open School of Gemology. Licensed under CC By 3.0.

Some settings may hide inclusions located around the girdle.

cracks along girdle - diamond clarity
Tiny feathers along the girdle caused by carelessness during the bruting process. Photo by Open School of Gemology. Licensed under CC By 3.0.

Inclusions located directly above the culet can sometimes be reflected within the diamond. The result will make one inclusion look like many. Although reflections of unusual inclusions, like garnet crystals, may appeal to collectors, this effect typically lowers diamond value.

Reflections of inclusions above the culet will lower a stone’s clarity grade more than if the inclusion were located elsewhere.

Inclusions located near an area with high facet density (like under the crown facets) will have less visibility, because the light reflecting off the facets will distract from them.

Relief

Some clear or white inclusions, like diamond crystals, have less of an impact on a diamond’s appearance than darker inclusions, like diopside or graphite crystals. Generally, the closer an inclusion comes to the host gem’s color and refractive index, the lower its relief or contrast. Therefore, in diamonds, clear or white inclusions have lower relief than dark inclusions.

Type

Different types of inclusions impact diamond clarity to different degrees.

For example, twinning wisps are white strain marks that form when the diamond crystal changes direction while growing. Since they radiate outward from the center of the stone, they affect clarity greatly.

twinning - diamond clarity
Several twinning lines in the crown as seen from the pavilion (10X). Photo by Open School of Gemology. Licensed under CC By 3.0.

Pinpoints, on the other hand, are tiny crystals barely visible under 10X magnification. They will have little effect on diamond clarity.

Feathers and chips can also have significant impact on the stone, depending on their size and location. A diamond can have a high clarity grade, even if it has tiny feathers along the girdle. However, a large feather may cause the stone to crack. Such an inclusion will drop the clarity grade dramatically.

fracture - diamond clarity
This fracture mark, perhaps caused by pressure or blow, may threaten the stability of this stone. Photo by Open School of Gemology. Licensed under CC By 3.0.

Plotting Diagrams

A diamond grading report should come with a plot or visual diagram of the stone’s inclusions. (You can see examples of these to the left of the photos in the “Diamond Clarity Grades” section above). This plot helps identify the diamond and also helps the buyer understand the diamond’s clarity characteristics.

Please note, a plot won’t contain all inclusions in a diamond. (It would look like a mess). Only the inclusions that set the grade are plotted.

One inclusion, however, is always plotted: the laser manufacturing remnant. This artificial inclusion results from the use of a laser (of course) to treat high-relief inclusions. In cases where such an inclusion is highly visible, such as below the table, a laser may be used to make a small channel to the inclusion. This allows acids or bleaching agents to reach the inclusion and either dissolve or lighten it. Usually drilled perpendicular to the table, the channel looks like a white pinpoint from the face-up position. However, when viewed from the side, the channel will appear as a thin white line.

laser drill holes - diamond clarity
Three laser drill holes, seen from the side (30X), with cleavage cracks at the end of each channel. Photo by Open School of Gemology. Licensed under CC By 3.0.

Carat, Color, Cut, and Clarity Working Together

The larger the carat, the more obvious the other qualities become. So, the larger the diamond you buy, the higher the color and clarity grades you should look for.

A stone much larger than one carat should usually have a clarity of VS2 or higher and preferably a color grade around G or H. For more color and clarity combinations, read these recommendations.

No matter the carat, color, and clarity of the diamond, always choose a cut grade of Excellent or, at the very least, Very Good.

Keep these points in mind:

  • Always go with what looks best within your budget. These are recommendations, not hard and fast rules. Although two stones may have the exact same grades, they won’t necessarily look the same.
  • These recommendations have more to do with a stone’s value than appearance. A particularly low grade in one of the Four Cs will diminish the value of a higher grade in another. Since the Four Cs work together seamlessly, a diamond will be a better deal and hold its value more if well rounded in all quality areas.

If you’re not sure what’s best, check out our recommendations to get the most from your engagement ring budget.

And, if you’re buying online, it’s essential to buy from a dealer that provides close-up video of your diamond. James Allen and Blue Nile have extensive databases of diamonds and offer magnified, 360° views of each one. This will let you see for yourself how the diamond’s clarity impacts its beauty.

Four Cs Chart Color carat clarity cut - diamond clarity
Chart of carat, color, cut, and clarity qualities. Licensed under CC By 3.0.

About the author
Phoebe Shang, GG
A gem lover and writer, Phoebe holds a graduate gemologist degree from the Gemological Institute of America and masters in writing from Columbia University. She got her start in gemology translating and editing Colored Stone and Mineral Highlights for a professor based in Shanghai. Whether in LA, Taipei, or New York, Phoebe spends her time searching for gems to design and being lost in good books.
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