Diamond clarity describes how free a diamond is of internal features, called inclusions, and surface features, called blemishes. GIA's clarity scale has 11 grades, from Flawless (FL) down to Included (I3), and graders assign them by examining the stone under 10x magnification. Most diamonds sold in jewelry sit in the middle of the scale, and many of them look clean to the unaided eye.
Inclusions and blemishes
Nearly every natural diamond contains some trace of its growth deep in the Earth. These features fall into two groups.
Inclusions are inside the stone or reach into it from the surface. They include tiny crystals of other minerals (or of diamond), pinpoints, clouds of pinpoints, feathers (small fractures), needles, graining and cavities. Many of them formed as the crystal grew in the mantle, which is covered on the diamond geology page.
Blemishes sit on the surface. They include scratches, nicks, polish lines, extra facets and small naturals (bits of the original crystal skin left on the girdle). Many blemishes come from cutting or wear and can sometimes be removed by repolishing.
The diamond inclusion library describes each type in more detail.
The GIA clarity scale
| Grade | Name | What a grader sees at 10x |
|---|---|---|
| FL | Flawless | No inclusions or blemishes |
| IF | Internally Flawless | No inclusions, only minor blemishes |
| VVS1, VVS2 | Very, Very Slightly Included | Inclusions so slight they are very difficult to see |
| VS1, VS2 | Very Slightly Included | Minor inclusions, difficult to somewhat easy to see |
| SI1, SI2 | Slightly Included | Inclusions noticeable at 10x |
| I1, I2, I3 | Included | Obvious inclusions that may affect transparency and brilliance |
Flawless diamonds are rare, and true FL stones make up a tiny share of the gem diamonds graded each year. The I grades cover stones where inclusions are easy to see and, at the low end, can affect durability.
The American Gem Society once used a numeric 0 to 10 scale that maps onto these grades, described on the AGS report page. Some European labs follow international nomenclature that uses "loupe clean" for the top grade, but the structure of the scale is broadly the same.
How graders decide on a grade
A grader looks at five factors for each clarity characteristic.
- Size. Larger features lower the grade more than small ones.
- Number. A single pinpoint counts for less than a scattering of them.
- Position. An inclusion under the table is easier to see than one near the girdle, and some positions reflect across many facets.
- Nature. A feather that reaches the surface raises different concerns from a tiny internal crystal.
- Color and relief. Dark or high-contrast inclusions stand out more than colorless ones.
The grade reflects how easily a trained grader can see the features at 10x, so the most visible feature often sets the grade. Graders examine the stone face-up and through the pavilion, and they decide on the grade from the face-up view.
What each grade looks like when worn
The grade differences near the top of the scale only show under magnification. Here is how the grades tend to look to someone wearing the ring.
- FL and IF stones look the same to the unaided eye as VVS and most VS stones. Buyers pay for rarity, not visible difference.
- VVS1 and VVS2 inclusions are hard for a trained grader to find even at 10x.
- VS1 and VS2 stones are almost always eye-clean in rounds and most other brilliant cuts.
- SI1 stones are often eye-clean, especially in brilliant cuts. They are a popular choice for buyers who want size within a budget.
- SI2 stones vary widely. Some are eye-clean, and others show inclusions from the top.
- I1 to I3 stones usually show inclusions to the eye, and large feathers can weaken the stone.
Eye-clean
"Eye-clean" means that no inclusions show when the diamond is viewed face-up without magnification at a normal distance, usually taken as about 25 to 30 cm. It is a trade term, not a grade, and it does not appear on GIA reports.
Whether a stone is eye-clean depends on more than its letter grade. The cut style matters: step cuts such as emerald and Asscher cuts have broad, open facets that act like windows, so they usually need a higher clarity grade to look clean than a round brilliant does. Size matters too, since inclusions are easier to see in larger stones. The best way to judge is to look at the stone itself or at high-magnification images from several angles.
How clarity is plotted
Many grading reports include a clarity plot, a diagram of the diamond seen from the crown and from the pavilion with the main clarity characteristics marked. GIA uses red symbols for inclusions and green symbols for blemishes, with black marking extra facets. A legend next to the plot names each symbol.
The plot is a map, not a photograph. Symbols are not drawn to scale, and small or repetitive features such as pinpoints and minor clouds are often summarized in a comment instead of being drawn. Even so, the plot is useful for confirming that a stone matches its report, since no two diamonds have the same inclusion pattern. The guide to diamond certificates covers the rest of the report.
Clarity, durability and treatments
Most inclusions have no effect on durability. Large feathers are the exception, especially ones that reach the surface near the girdle or a corner. A hard knock at the right point can extend a feather, and setting pressure can do the same. Ask a jeweler to check the location of any sizable feather before setting.
Some diamonds are treated to improve apparent clarity. Laser drilling burns a narrow channel to a dark inclusion so it can be bleached with acid, and fracture filling introduces a glassy material into feathers to make them less visible. GIA grades laser-drilled diamonds and plots the drill holes, but it does not grade fracture-filled diamonds. The diamond treatments page explains how these work and how to spot them.
Clarity in fancy shapes and fancy colors
Clarity matters less to the eye in brilliant-cut shapes such as round, oval, cushion and pear, because their facets break up light into many small reflections that camouflage small features. Step cuts reveal more. In fancy colored diamonds, color dominates value and inclusions are less obvious against strong color, so buyers often accept lower clarity grades.
Frequently asked questions
What is the best clarity grade for the money?
Many buyers choose VS2 or SI1 stones that have been checked for eye-cleanliness. They look the same face-up as higher grades for much less money.
Can you see the difference between VVS and VS?
Not without magnification. The difference shows only under a 10x loupe or microscope, and even then it can be hard to find.
Do all diamonds have inclusions?
Almost all do. Flawless and internally flawless stones exist but are rare.
Can a clarity grade change?
A diamond can drop a grade if it chips or a feather grows through damage. Repolishing can remove blemishes and sometimes raise a grade slightly at a small cost in weight.