The girdle is the widest part of the stone. Traditionally it has been
left in rough, so it looks like a ground glass. However, in the past few
years a lot of stones have faceted girdles, 32 facets all the way around.
You might also see a polished girdle.
Judging the Girdle
The girdle should not be too thick or too thin. The more uniform around
it is the better. On most certifications, the girdle will be described
as 'thin, 'medium', etc., or as within a range, such as 'very thin to
thin'. Stay away from diamonds having a sharp, knife-edge girdle, the
diamond may more easily become chipped during mounting or wearing.