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Will a feather EXPLODE my diamond?

Crack! Fracture! Cleavage! Gletz!

Okay, the last term isn’t as scary as the others, but all of these words are used to describe one of mother nature’s most common clarity characteristics.

The feather.

The dreaded feather.

That notorious, ticking-time-bomb that could cause your diamond to EXPLODE!

Photo credit: Unsplash


Some think so. And who can blame them? To skeptics the name “feather” may seem like a diamond marketing abatement. A jewelry-industry conspiracy to soft-sell what should be disclosed as a crack in the diamond.

They just want to know. “Is that feather – that crack in my diamond – a cause for concern?”

Yes and no.

Does a crack in the sidewalk trip you up, if you don’t see it? Some yes. Some no. It’s the same with diamonds. Every diamond is different. Every feather is different. And there are other variables to consider. What’s the shape of the diamond? What’s the location of the feather? What direction does it run? What’s its size and severity? What other inclusions and blemishes are present? Does the diamond have internal strain? Is the feather inert or could it expand?

Spoiler alert: There’s a SIMPLE answer for all of this (You can skip to “The answer” at the bottom if you’re pressed for time…otherwise I’ll try to keep you entertained a bit longer).

Technical definition

According to the IGI Diamond Grading Manual

A feather is a separation or break due to a fracture, often white and feathery in appearance.

“A break? A fracture? So yes, my diamond could EXPLODE!

Image credit: Eduardo Mehl

No. It won’t and here’s why.

Finished diamonds have already been through more intense pressure and friction in sawing, girdling, blocking and polishing than they’ll ever see again during normal wear. Even the relatively gentle final phases cause enough pressure and friction that diamonds turn red-hot on the polishing wheel.

Photo credit: Pollard Professional Services

Diamonds have enormous value so producers take precautions, especially with challenging crystal types, examining growth-directions, using cross-polarized filters to check for internal strain and correlating sensitive areas with the inclusions present prior to polishing.

With that said, diamonds can and do break during the cutting process, sometimes violently. This is where the notion of exploding comes from – trauma during initial production, repair or recut. Every diamond cutter has a favorite ‘exploding diamond’ story. But once the diamond is finished and mounted there’s no such thing as ‘spontaneous diamond combustion.’

Then why so many scary words and warnings?

Because feathers of a certain size and position MAY pose a risk to a diamond’s durability, now or in the future. Not all of them. Not most of them. But they’re out there.

“Breaking” news

A diamond’s clarity grade is key to understanding a feather’s implications. The clarity grade is based on size, frequency, location, type and visibility of all the diamond’s collective characteristics. With that said, a feather, when present, will frequently be the most influential characteristic or “grade-setting” inclusion. And feathers occur at every grade from VVS1 through I3.

Feathers in VVS grades

  • Older methods of bruting (shaping a diamond’s girdle) caused what’s called bearding; tiny, microscopic feathers along the girdle. In some cases this is so insignificant that the diamond could remain  VVS1 or VVS2.
  • Whether bruted or faceted, hairline feathers at the girdle tend to fall into VVS1-VVS2 much of the time.
  • VVS1-VVS2 feathers may even be considered to have less impact than pinpoints, needles or clouds.

Feathers in VS, SI and I grades

This VS2 feather is a nice example of a benign grade-setter. It’s small, nearly invisible and occurring into the body, away from the girdle, in this 6.03 carat diamond. We can all move along. Nothing explosive to see here.

See the full IGI Diamond Grading Report: 6.03 carat L VS2 EX

SI1 feather

This video shows a nice example of a grade-setting SI1 feather which is also benign and largely transparent. Its central location absolves it of any pressure-release concerns during stone-setting. It’s also less noticeable against the light background than the accompanying, opaque crystals. In fact its mere presence will reduce the price from some higher range to the SI1 range for potential buyers. If it’s invisible to the naked eye, this is a fairly friendly feather indeed.

I1 feather

Unlike the examples above, the feather in this diamond could pose a risk to the stone’s durability. It’s size and position at/along the girdle could cause it to expand or fracture if subjected to forceful pressure when being set. An accidental impact in that area during daily wear could also cause expansion or fracture.

See the full IGI Diamond Grading Report: 0.50 carat I I1 VG

“Step on a crack ~ break your diamond’s back”

There is one significant factor after the cutting process which must be considered when handling diamonds with feathers near the girdle. That factor is the professional knowledge and skill of the stone-setter. And where this applies to all diamonds it’s acutely important for shapes with corners and points.

For example, the four corners of a princess shape are placed into different seats at each of the prongs.

What happens if the stone-setter applies uneven pressure when seating a princess cut with a VS2 feather in the corner? Now there is pressure within the diamond, caused by the setting itself. A few months later the ring takes a knock against a counter, the pressure releases, and…


Poor feather. They’ll blame you. But it wasn’t your fault.

“The Answer”

The first and last word is this: The clarity grade printed on your gemological institute’s diamond grading report is the most authoritative, expert indication of your feather’s potential behavior.

If we set aside the human stone-setting interference described above –

  • A VVS or VS feather should be no cause for concern
  • The same applies to feathers in the SI1 and SI2 range, although the skill of the stone-setter comes into play with greater frequency in that range. Caution should also be exercised in daily wear to avoid trauma which could cause a feather to expand.
  • Diamonds with feathers graded I1, I2, or I3 should be considered on a case by case basis.

Those grades, I1, I2, I3 (where I stands for “included”) are specifically reserved to indicate (1) a serious threat to durability or (2) inclusions so significant that they impact transparency and brightness. It could also be the combination of both factors.

Example of I3 clarity

Treat your diamond like your car

No one wants to experience a fender-bender, but accidents happen. So when “driving” your favorite jewelry, remember that every diamond has cleavage planes as part of its crystal structure. And while they are the hardest known natural substance a knock the wrong way, particularly at the girdle, can cause even a flawless diamond to chip.

This goes for any diamond and is why it’s good to protect your sparkling diamonds and jewelry with a good insurance policy, just as you do your sparkly, shiny, automobile.

Photo credit: Car and Driver

John Pollard

John Pollard is Senior Director of Education for IGI, overseeing and expanding the institute’s traditional educational offerings and diploma programs, instructed at 14 schools of gemology around the world, along with customized eLearning courses, tutorials, seminars, and webinars for IGI clients across all sectors, including leading luxury brands.

This Post Has 6 Comments

  1. Rayana

    so crazy 🙂

  2. Sadye

    Тhis information is іnvaluable.

  3. Dianne

    Hi there! This is my first comment here so I just wanted to give a quick shout out and say I really enjoy reading through your blog posts. Can you suggest any other blogs/websites/forums that cover the same topics?

  4. ปั้มไลค์

    Like!! I blog frequently and I really thank you for your content.

  5. Jyoti Prakash Das

    Very much informative. Thanks.

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