An extra facet is a facet that the cutting style doesn't need, placed without regard for the stone's symmetry. It is most often near the girdle.
In more detail
It is a blemish, and it also counts as a symmetry fault. A small bottom facet that isn't parallel to the table counts as an extra facet, not as a culet.
On a grading report
Drawn in black on GIA's clarity plot and listed last in the key to symbols.
Related terms
- Blemish: A blemish is a clarity characteristic confined to the surface of a diamond.
- Culet: The culet is the bottom point of the pavilion. It can also be a tiny facet, parallel to the table, that keeps the point from chipping.
- Symmetry: Symmetry is the report grade, from Excellent to Poor, for the exactness of a stone's outline. It also covers the shape, placement and alignment of the facets.
- Natural: A natural is a part of the rough diamond's original surface left on the cut stone. It is usually on or near the girdle.