External Diamond Clarity

Imperfections, Irregularities and Blemishes

This page has advanced technical information about external diamond clarity. If what you need is an overview, then please read our diamond clarity page. If you would like to know our diamond quality policy, then please see the introduction of our Guide to Buying Engagement Rings.

A diamond's external imperfections or irregularities - those that are confined strictly to the surface of a diamond - are often referred to as 'blemishes'. When your diamond is graded, its characteristics will be marked on your certificate. These characteristics may be on the diamond's external surfaces or internal in the diamond crystal itself.

Diamond Clarity

Listed below are some terms used to describe external blemishes found on a diamond's surface - it may be interesting for you to read on and find out what they mean:

'Abraded' facet edges or culet

Resulting from heavy wear and tear over a long period of time. It will appear white frosted or have a sandblasted look which under magnification can be seen as a series of minute nicks.

Burn Marks

Burn marks can result from friction during the polishing process creating a cloudy or frosted surface. They may occur during repair, from the heat of a jeweller's torch

Cavity, Nick or Pit

These are an opening in the polished surface of the diamond that would cause a loss of carat weight if removed.


A chip is a shallow opening into the diamond stone usually with an uneven or stepped surface. Severe chips can alter the outline of the diamond.

Extra Facet

Placed without regard to a stone's symmetry, extra facets are commonly used to polish out minor blemishes. When not visible directly through the crown, they are not considered a blemish but would still be marked on a plotting diagram. An extra facet will be polished with straight edges and polishing lines. In some cases, where facets over and above the normal number have been added as part of the cutting style, "additional facets" can be used or may be described as, for example, "modified brilliant" or "modified princess cut".

Girdle Roughness

This is the result of rough or fast bruting of the girdle.

Grain Lines

These result from irregularities in natural crystallisation.


Remnants of the original rough diamond's surface which are left on the polished diamond, frequently on or near the girdle. While these are blemishes, they indicate a sign of skilled cutting, as the cutters try to spread the stone and retain as much of the original crystal's weight as possible. In many cases, naturals do not affect the clarity grade, but when found on or near the girdle, the stone's girdle directly opposite should be examined as a corresponding natural is often found there. Naturals are proof that the stone is indeed a natural diamond.

Indented Naturals

A natural which interrupts the girdle of the diamond but would cause weight loss if polished out.

Percussion Marks

Result of a sharp blow to the diamond's surface, creating an indentation with very small cleavage fringes. Often seen as small white spots on the edges between facets.

Polishing Lines

Polishing lines may appear as parallel irregularities on the surface of the gem but are rarely heavy enough to lower the clarity grade of a diamond. However, visible polishing lines will diminish the diamond's 'finishing' grade.


Fine white lines as the result of diamonds coming into sharp contact with each other.

Let's Go Shopping for an Engagement Ring

Diamond Engagement Rings Hopefully we've covered all the important things you need to know about engagement rings. If you still have any questions, there's plenty of information in the rest of our Guide to Buying Engagement Rings, or you can always contact us and we'll be happy to help.

If you are ready, let's go shopping.

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