Learn: Diamonds > Fish-Eye

Have you ever wondered what a fisheye is and how to find one? Let us help you learn a lot more about this common problem. To put it simply, it is a nasty appearance that you can see just inside the table of a diamond. It looks slightly crazed and dull, just like a dead fishes eye. The fish-eye is a reflection of the girdle (on the opposite side). If the girdle is not polished and is thick the effect looks like a BIG circular inclusion and can be as bad as an I3 (P3).

Fish-eyes are more apparent if the pavilion is shallow 39.5°, the table is large; the girdle is thick and not polished. Combinations of these factors worsen the effect.

Holloway Cut Adviser test takes fish-eye into account. They occur between the following pavilion depths and table sizes:

41-degree pavilion and 72.2% table

39-degree pavilion and 58.4% table

Diamonds with these proportions show fish-eyes that require no tilt to see them. If the table gets 1% bigger you see a 1% more fish-eye.

We downgrade these flaws in value, a bit like an inclusion because that is what they look like.

A Holloway Cut Adviser test and report will give you a ” do not buy this diamond under any circumstances as it is a fish-eye ” comment if it is very bad.

A small amount of tilt to see flaws is acceptable because these diamonds have a very good spread and look very big for the money. If the fish-eye can only be seen with 5 degrees or more tilt then we consider the diamond to be ideal.