Diamond Blemishes: Surface Graining | Rare Carat

Surface graining shown on a GIA certificate

You’re (about to be) engaged! YAY! In order to get you on that path to victory, we want to make sure that you take a look back at all of our previous blog posts, especially those relating to diamond inclusions. There’s a wealth of information there to get you on track. We suggest you begin with our intro on diamond imperfections before you hurl head-first into something like surface graining, as it will give you a nice bit of foundational knowledge for you to sink your teeth into. Click here for that intro.

What is Surface Graining?

When discussing surface graining, it’s important to point out that unlike some of our other blemishes (I’m looking at you burn marks), surface graining is not actually the result of some dodgy diamond polish job. Instead, it is a natural occurrence and the result of the diamond crystal itself; some areas growing faster than others, for instance.

Surface graining can look a little like polish lines or streaks on a window - but unfortunately, unlike polish lines, they cannot be removed with a re-polish! This is because they are part of the crystal’s natural structure (rather than human error like polish lines/burn marks etc.). Here’s an example of those streaky offenders.

Round diamond against a white background with two circles around lines on the diamond called "surface graining"

Not only are they a permanent and often unsightly fixture, but they can also impact the clarity of the stone in a bad way. That’s because all those nasty streaks are impeding the light from getting in and bouncing around inside that diamond (which is what makes the whole thing sparkle in the first place). Less light means the diamond can appear lifeless, which is the opposite of the goal.

Surface Graining Diamond Blemishes FAQs

If a diamond has surface graining, does that mean it’s a poor buy?

Not automatically—but it’s a reason to proceed with care. Since surface graining is part of the crystal structure and can’t be polished away, it can affect clarity or brilliance if the streaks are dense or in a visible area. If it’s subtle and tucked away, it may not be a serious issue.

What should I check when I see a diamond listing that mentions “surface graining”?

Ask for magnified images or videos and look at how visible the graining is under typical lighting and face-up. Also check where it sits—if it’s right under the table or near the edge, it’s more likely to affect light return. Make sure you understand whether the graining impacts how the diamond appears and performs.

Will polishing the diamond remove this blemish?

Surface graining is built into the stone's structure, unlike other blemishes such as scratches or polish lines. So, it is permanent, and polishing the blemish won't remove it.

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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.