Diamonds 101: Clarity


Diamond clarity is a measure of the quality of diamonds, based on the existence and appearance of internal characteristics called inclusions, and surface defects called blemishes.

It is one of the four Cs of diamond quality, along with carat, color and cut.

A clarity grade is given to diamonds based on the appearance of the stone when magnified by ten times. Higher clarity diamonds are more valuable, with rare 'flawless' graded diamonds carrying the highest value.


What are inclusions?

Inclusions are internal characteristics, including clouds, feathers, knots and cavities, which affect a diamond's clarity.

Most inclusions do not affect a diamond's structural integrity are not visible to the naked eye – however, larger ones can affect the stone's ability to transmit light and make them more vulnerable to fracture.

Inclusions are normally natural, caused by crystals of a foreign material or structural imperfections such as small cracks. But they can also be caused by synthetic enhancement processes – laser lines, for example, are considered inclusions.

Some inclusions are considered useful as marks of identification and proof of natural origin.


What are blemishes?

Blemishes are defects to the surface of a diamond, including polish lines, grain boundaries, scratches and cracks.

Like with inclusions, many blemishes are natural parts of the gem – but others occur either when the diamond is cut and polished or while it is being worn.


How is diamond clarity graded?

There are various systems of grading diamonds, depending on the organization and area of the world.

In America, the most commonly used grading system is that of the Gemological Institute of America (GIA). It uses a scale divided into six categories and eleven grades, as follows:



Internally Flawless

Very Very Slightly Included

Very Slightly Included

Slightly Included















Flawless (FL): No inclusions and no blemishes at 10x magnification.

Internally Flawless (IF): No inclusions visible at 10x magnification.

Very, Very Slightly Inlcuded (VVS1 and VVS2): Inclusions slight enough to be difficult to see by a skilled grader at 10x magnification.

Very Slightly Included (VS1 and VS2): Minor inclusions can be seen at 10x magnification.

Slightly Included (SI1 and SI2): Noticeable inclusions at 10x magnification.

Included (I1, I2 and I3): Obviously inclusions at 10x magnification, which could affect transparency and brilliance.


Many inclusions and blemishes are too small to be seen by the naked eye. A VS1 and SI2 diamond might look the same to the average person, which is why expert grading assessment is important in determining the value of a diamond.

Diamonds without visible inclusions when examined from six inches away are known as “eye-clean”.


What factors are considered when grading diamond clarity?

A diamond grader will study five factors when making an assessment on a diamond's clarity: the size, number, position, nature and color or relief of inclusions and blemishes.

Size: Naturally, larger inclusions tend to be more noticeable under magnification and therefore result in a lower grading.

Number: Generally, the more inclusions the lower the clarity grade.

Position: The position of an inclusion affect how visible it is, and the degree to which it changes the way the stone reflects light.

Nature: The nature is what kind of inclusion or blemish is found – internal characteristics include bruises, chips, clouds, knots, laser holes, needles and pinpoints, while external characteristics include abrasions, nicks, polish marks, scratches and extra facets. The nature also takes into account the risk an inclusion causes to further breakage of the stone.

Color or relief: Characteristics are said to have “relief” if they contrast with the surrounding diamond. Colored inclusions tend to be more easily seen.


How does grading affect value?

Increasing clarity generally means increasing value, with VVS, IF and FL gradings leading to the highest prices. FL and IF grade stones are sometimes called “museum quality” or “investment grade” diamonds due to their rarity.

Only around 20% of all diamonds which are mined have a high enough grading to be considered appropriate as gemstones – the other 80% are used industrially.


How can diamond clarity be enhanced?

Colored inclusions can be treated by a laser “drilling” process, which burns a hole into the inclusion and washes it with acid to remove the color.

Clarity can also be enhanced by filling cracks and fractures – these are sometimes called “fracture-filled diamonds” and are often available at a discount price.

The GIA will not grade fracture-filled diamonds as the treatment is not considered to be permanent – but because laser drilling is considered to be a permanent treatment, these diamonds can be graded by the GIA.



Diamond grading is a complex process involving a wide range of variables.

It is important for buyers to consider that they are likely to pay higher premiums for higher clarity diamonds, even if they and others cannot tell the difference with the naked eye.