Diamond Expertise

Diamond Inclusions

Find out what is an inclusion in a diamond, the different types of diamond inclusion, plus how they are graded and valued, in our complete diamond inclusion guide - written and curated by the expert gemmologists at Queensmith.

What is an inclusion in a diamond?

Diamond inclusions are the naturally occurring ‘flaws’ that almost all diamonds contain. Inclusions appear as small marks or blemishes within the diamond. Completely flawless diamonds contain no inclusions, and are incredibly rare. While almost all diamonds contain inclusions, some are so minimal and small that they are invisible to the naked eye, without magnification - these diamonds offer the best value for money versus beauty.

How are inclusions in a diamond graded?

The GIA assesses diamond inclusions and blemishes in detail, in order to provide an overall clarity grade. The presence, type, severity and location of each inclusion or blemish is assessed and recorded. Once the diamond grader is satisfied that each inclusion has been identified, they will take five factors into account to determine the overall clarity grade: the size, number, position, nature and colour of the inclusions. Clarity is graded on a scale, from IF (internally flawless) to I3 (severely included).

What are the different diamond inclusion types?

The small marks and flaws found within diamonds are given the umbrella term ‘inclusions’, but there are many different types of diamond inclusions, caused by different phenomena. Some are more notable than others:

  • Crystal - a minuscule diamond (or other mineral) within the diamond; sometimes coloured

  • Pinpoints - tiny white or black crystals, appearing like a pinprick within the diamond

  • Needle - an elongated, thin line of crystal

  • Cavity or chip - usually caused by stressing a weak point during diamond cutting, a cavity in the surface

  • Feathers - an internal crack or fissure, appears light and feather-like, sometimes transparent without magnification

  • Clouds - a cluster of pinpoint inclusions, which can make a diamond appear milky or hazy

  • Knot - a small crystal that breaches the surface of the diamond, like a tiny bump on the surface

  • Graining - like you might find in wood, long streaks or lines that can look like scratches within the diamond, usually more visible from certain angles of the diamond

  • Twinning wisp - these show the moment a diamond stopped then restarted growing; often two amalgamations of pinpoints, needles, feathers and cloud inclusions that point to separate phases of growth

Images via gia.edu
Internal Graining
Twinning Wisp

What causes diamond inclusions?

Inclusions and blemishes appear in almost every diamond during its growth period. Natural diamonds form under the intense heat and pressure of the Earth’s mantle, the perfect environment to encourage the crystalisation of carbon molecules, which eventually form the sparkly stones. The growth of each diamond will undergo its own irregularities and growth patterns - just like snowflakes, every diamond is formed with unique characteristics and inclusions. See the list of diamond inclusion types below to see what causes different inclusions.


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Diamonds without inclusions are rare - and expensive! The odd, small inclusion is no bad thing, just make sure it isn't visible without magnification and is not located at the centre of the diamond.

Sarah Jane | Senior Gemmologist & Design Expert
Queensmith consultant and gemmologist, Sarah Jane, laughing and smiling at the Queensmith showroom in Hatton Garden

What’s the difference between diamond inclusions and blemishes?

A diamond inclusion is a flaw or irregularity within the diamond, while a blemish is a flaw or irregularity on the surface of the diamond. Together, inclusions and blemishes are considered clarity characteristics.

Are there benefits to a diamond containing inclusions?

Yes - there are benefits to a diamond containing inclusions. The main benefit is that a diamond with inclusions is considerably less costly than a flawless diamond. That said, inclusions can disturb the beauty of the stone when they are large or severe enough to be seen without magnification, and obstructive enough to restrict light reflection. Inclusions are natural, and some admire the presence of inclusions, indicative of its history and natural origins. Fake or imitation diamonds won’t contain inclusions so you may agree that any flaws help determine the authenticity of the stone. Our advice is to look for a diamond with minor inclusions, graded between VS2 to SI1, for the best value for money versus beauty.

How do diamond inclusions impact diamond cost?

Heavily included diamonds retail at far lower costs than flawless or near-flawless diamonds. As the GIA state, the influence of inclusions on diamond price is directed related to value. The closer to flawless a diamond is, the rarer and more desirable it is - therefore the higher the cost of the diamond. Diamonds graded between VS2 and SI1 are considered the best value for money - they’ll appear flawless (or very nearly flawless) to the naked eye, but retail at significantly lower prices than flawless diamonds.

How rare are diamonds with no inclusions?

Internally flawless diamonds, graded FL, are so rare that many gemmologists and jewellers could go their whole careers without seeing one. The fewer inclusions in a diamond, the rarer it is. If you have your heart set on an extremely clear diamond, say VVS1 to VVS2, you may need to be patient with your diamond search, as such high clarity grades are rare. We advise looking between VS2 to SI1, where you’ll see a great range of diamonds, still with minimal inclusions.

Diamonds almost always have some kind of inclusion. For diamonds with inclusions invisible to the naked eye, look at clarity grades above SI1, ideally up to VS2 or VS1 for the best value for money.

Sarah Jane | Senior Gemmologist & Design Expert

Why do diamonds have inclusions?

Both lab grown diamonds and natural diamonds typically feature inclusions, and it is very rare to find a diamond without any inclusions. As diamonds form, whether in a laboratory or within the Earth’s mantle, they can experience growth irregularities that result in tiny cracks, fissures or the presence of miniature crystals within the main diamond crystal.

Do lab grown diamonds have inclusions?

Yes, lab grown diamonds typically feature inclusions, just like natural diamonds do. The process of creating a lab diamond mimics the intense heat and intense pressure of natural diamond formation within the Earth’s mantle, and small flaws and irregularities can occur in the same way during the growth period. Lab diamonds grown in a molten metal solution can feature small metallic inclusions, which natural diamonds do not.

Do a diamond’s inclusions impact its sparkle?

A diamond graded above SI1 will have lustrous sparkle despite the internal inclusions: the inclusions will be small and minimal, and not noticeably disrupt any sparkle. Instead, the cut grade of the diamond is much more pivotal in determining the sparkle. However, a heavily included diamond graded below SI2 will sparkle a little less, particularly when the inclusions are visible to the naked eye. Heavy inclusions will disrupt the path of light return bouncing around within and out of the diamond, meaning light emitted from the diamond is weaker. In short, a diamond with heavy inclusions will not have a great sparkle.

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