Inclusions & Blemishes

Diamond Inclusions: Knot | Rare Carat

Diamond knot shown on GIA certificate

Knot as represented on GIA report

What is a Knot?

‘KNOT’ to sound overly alarmist here (I couldn’t help myself), but knots are bad news.

Knots are caused when a 'crystal' reaches the surface of a diamond. The difference between a knot and a crystal though is that a crystal rarely distorts the stone's shape or causes durability issues.

Not only are knots usually pretty visible within the stone (and it mightn’t even take a magnifier to see them either), but they also negatively impact the overall durability of a diamond.

Round diamond with a red circle around a black crystal reaching the surface

This is an extreme example, but still. Knots can’t keep to themselves. They widen. They fracture. They crack. If the remaining crystal falls out, the knot can leave a huge cavity behind. Trust us, just avoid them.

Knot Diamond Inclusion FAQs

What exactly is a “knot” inclusion in a diamond, and how does it form?

A knot occurs when a crystal inclusion inside the diamond reaches the surface of the stone. Unlike a crystal that stays fully inside, a knot becomes part of the surface and may alter the shape or structure slightly, making it more visible and potentially fragile.

Should a diamond showing a knot always be ruled out?

Yes—for the most part. The article states that knots are high‑risk because they are often visible without magnification and can compromise the durability of the diamond. For that reason, Rare Carat recommends avoiding stones with knot inclusions when possible.

How can I recognize a knot inclusion when reviewing a diamond listing or certificate?

When a grading report or certificate mentions “knot,” check for a visible crystal touching or breaking the surface. Ask for high‑resolution images or videos of the diamond, especially from multiple angles, and look for any irregularity on the surface or facet where the knot sits. If it’s noticeable to the naked eye or near a vulnerable edge, it’s a red flag.

How might a knot affect a diamond’s value or future durability?

Because a knot involves a surface‑reaching inclusion, there’s added risk: the crystal might drop out, leaving a cavity, or the area around it might fracture. These possibilities mean the diamond could lose brilliance or structural integrity over time. In practice, this tends to lower both the value and the confidence a buyer should have.

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Dr. Rian Mulcahy

Rian is officially a Diamond PhD - just ping us if you’d like to read her fascinating 200-page thesis, titled Facets of Value: An Investigation into the Formation of Worth in the Diamond Market. She has consulted various firms all along the pipeline, from the rough diamond market to the recycled diamond industry. She holds an MA in Globalisation and Development from University College Cork and a PhD in the Sociology of Diamond Valuation from the London School of Economics.