A bow-tie is a dark band across the belly of an oval, pear, marquise or other elongated stone. It is not an inclusion or a color: the facets there send little light back to the viewer.
In more detail
GIA's guides call it a reflection of the viewer's head and shoulders. They add that the shape and facet pattern play a part. In DG's ray trace of a diamond, belly facets over about 51.9° let head-on light leak out through the back. That leakage makes a dark band too, and the room light decides how dark either kind looks.
On a grading report
A GIA report gives fancy shapes no cut grade and says nothing about a bow-tie. IGI's optional fancy-shape cut grade checks for bow-ties, and the AGS Ideal Report's ASET map covers some ovals.
Related terms
- Belly: The belly is the wide middle of an elongated stone such as an oval, pear or marquise.
- Fancy shape: A fancy shape is any diamond outline other than round, such as oval, pear, marquise, cushion, princess or emerald.
- Length-to-width ratio: The length-to-width ratio of a fancy shape is its length divided by its width, both taken from the measurements.
- ASET map: An ASET map is a four-color picture that shows from which directions a stone's face-up light comes. It can be part of the AGS Ideal Report by GIA.
- Leakage: Leakage is light that enters a stone and leaves where the viewer cannot see it, mostly through the pavilion. Lower leakage is better.
- Contrast (Light Return): Contrast is the part of a face-up stone whose light comes from 75° or higher above the girdle plane. This zone lies within 15° of the line of sight, where the viewer's head is.
Learn more
- The bow-tie effect in diamonds: what it is
- What causes a bow-tie? Four explanations, tested
- Bow-tie in the stone, sometimes on your finger: tilt and head shadow
- Fixing a bow-tie: the steep belly of DG-Bowtie
- Bow-ties and grading reports: what the numbers can't tell you
- How to check a stone for a bow-tie: a bench routine
- The bow-tie effect