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Diamond inclusions: an overview

Some people call diamond inclusions flaws while others may see them as distinctive characteristics. Their presence signifies an imperfection but many would say that is what gives a diamond some of its personality and individual beauty.

As is common in nature, few diamonds are truly perfect and those few are exorbitantly expensive. Most diamonds you see have at least some small inclusions. Salespeople may tell that inclusions won’t affect the strength or beauty of the diamond but you should have an understanding of inclusions before making a decision.

Inclusions affect the clarity of a stone. Clarity is one of the ‘4 Cs’ of diamond grading and valuation along with colour, cut and carat size. Clarity is a description of how light passes through the stone. An inclusion may or may not interfere with the refraction of light inside a diamond and by extension, its value.

Diamonds are typically graded in a lab using a microscope with magnification power of 10 times the industry standard. Anything less isn’t considered an authoritative grading. A flaw can be external, like a chi,p but inclusions are usually part of the diamond itself and not caused by the environment or by cutting or polishing the stone. Inclusions can take many forms.



Most diamonds contain minerals and crystals embedded in their structure. A large grouping will detract from the stone’s clarity but a small grouping or a few individual crystals may not even be visible to the eye. An interesting or unusual crystal inclusion could even enhance its value.



A tiny crystal resembling a small point of lightness or darkness is called a pinpoint. These are the most common inclusions. Most aren’t visible without magnification and won’t affect value. However, a grouping of pinpoints creates a ‘haze’ or ‘cloud’ that can decrease clarity and thus value.



Crystals can take the form of long, narrow spikes or needles within the stone. They may not be visible to the eye and some may even give the diamond a special glimmer.



Clouds are groupings of three or more pinpoints located close together in a diamond. If visible, a cloud or group of clouds can diminish the stone’s clarity.



A knot can be a more problematic inclusion. When a crystal extends through a diamond to its surface, it’s called a knot. A knot may crease a raised area on a facet. A knot may weaken a diamond and jeopardise its durability.


Grain or growth lines:

As a diamond forms, it may crystallise irregularly. It may develop variations in its hardness that appear as microscopic lines across the facets. Grain lines can also be caused by improper polishing of the stone.



Feathers are cracks in the stone resembling their namesake. Feathers may signal a structural defect that could compromise a stone’s strength and longevity. If the crack reaches the surface, has a deep fissure, runs the major length of the stone or shows a stress point, then you could have a problem later.



An intergrowth will appear as a light-coloured, twisting strip within a stone. They usually occur in diamonds that literally twisted together during formation.



This is a straight crack with no feathering. It often runs parallel to one of the diamond’s planes and if pressure is applied at the right angle, can split the stone. Pressure may come from an accidental blow or the simple grip of a pronged setting.


Bearding or girdle fringes:

Hair-like lines may occur around the stone’s girdle during the cutting process. They may also be called dig marks. Bearding doesn’t usually devalue a stone or degrade clarity unless it’s extensive. Re-cutting is necessary to improve lustre.


Laser lines:

A laser line isn’t really an inclusion because it’s not part of the natural stone. However, when a laser is used to remove a dark inclusion, you may see a tell-tale trace of the machine-made trail that looks like a thread going from the surface towards the centre.


Some inclusions are red flags of poor stone quality and shouldn’t be ignored. But inclusions don’t always detract from a diamond. Like a face or a fingerprint, each diamond is unique and interesting due in part to its imperfections.

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