Answer: A feather is basically a soft word for a crack in the diamond. Usually, feathers in diamonds will take on a whitish or translucent appearance (Imagine a hairline crack within the crystalline structure of the stone). However, they can and do exist in other forms of coloration like black or brown.
Out of all the types of inclusions and flaws a diamond can have, feathers are the ones you probably need to take special note of.
You see, while it is true that diamonds are the hardest substance on Earth, they are still susceptible to chipping and cleaving when a force is applied in the correct direction along its crystalline plane.
Feathers in Different Locations
When a feather is located near the diamond’s girdle, it calls for a red flag. You need to be aware that the feather (crack) could grow in size if it is subjected to a hard knock or everyday wear and tear. Even if the current feather (indicated in red) is located inside the body of the diamond, it could still grow in size and reach the surface under unfortunate circumstances.
In the 2nd scenario, it is OK as long as the feather doesn’t reach the surface of the diamond and is eye clean.
In the 3rd scenario, I had purposely showed you one that might not be totally clear. Is the feather very near the diamond’s culet or is the feather deep inside the diamond’s body? The GIA report doesn’t tell you this in the inclusion plot. For example, the diagram below shows 2 diamonds which have similar 2D inclusion plots in the grading report.
Is it almost touching the surface or is it safely inside the body?
When in doubt, make sure you double check with the jeweler and ask him/her to show you the location of the flaw under a microscope. If a feather is located within the diamond’s body and away from the edges, it is generally OK and you wouldn’t have to worry about it once it is mounted onto a ring. In such scenarios, as long as the inclusion is not visible to the naked eye and don’t pose any durability issues, you are OK.