What Is Non-pointing (Ptg) Deviation in Diamonds? (Images)

In a well-cut diamond, all fully formed facets should reach their prescribed locations or be completely finished. Otherwise, inverse circumstances will result in adjoining facets not meeting at precise points.

In diamond symmetry, we call these deviations non-pointings (Ptg). Generally, they can be grouped into two broad sub deviations:

  • Short Facet: Facets that do not reach their prescribed locations
  • Open Facet: Facets that are incompletely finished

Non-pointing deviations can occur in various facets of a diamond. Depending on the facets they affect, the GIA identifies four specific deviations when assessing symmetry quality during the grading process of a round brilliant diamond's cut.

Non-Pointing Deviations on Diamond Crown
  • Short Bezel (SB): The point of the bezel that faces outwards meets earlier, not reaching the girdle edge. This deviation also induces adjoining, misshapen upper girdle facets.
  • Open Bezel (OB): The lower portion of the bezel isn't fully finished, missing a point that should meet or overlap the girdle. As a result, this bezel takes on a pentagonal shape, disrupting the balance of the adjacent upper girdle facets.
  • Short Main (SM): Similar to the short bezel, the point of the main facet (also known as the pavilion facet) facing upwards meets prematurely, failing to reach the girdle edge. This deviation is often associated with lower half variation (LHV), resulting in an imbalance of the adjacent lower halves.
  • Open Main (OM): The two lines of a main facet, adjoining the lower girdle facets, do not intersect. Instead, their hypothetical point of intersection lies outside the girdle.
Non-Pointing Deviations on Diamond Pavilion

All these symmetry variations can alter the routes of light reflection and refraction on/in a diamond. If you're drawn to a diamond's romantic "hearts and arrows" pattern,🏹❤️ you should pay closer attention to these non-pointing deviations as relevant facets, especially the main and related lower half facets, play a crucial role in creating and defining this distinctive pattern. All slight variations can skew many aspects, which will lead to queer, asymmetrical hearts and arrows.

When shopping for a diamond online, many vendors provide an option to filter stones with a particular symmetry grade. But if you are not buying a big stone and not very fussy about a precise look or pattern, there's no need to entangle yourself in sticking an Excellent symmetry. Instead, the generic 4Cs standard, including the overall cut grade, suffice to aid in your decision. Coupled with the evaluation with your naked eye on the visual light beauty, you can find your dream stone for your budget.

Leave a CommentReport an Error
=
=
Leave a Comment▾

Leave a Comment

Your email address will not be published. Required fields are marked *

linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram