Gemstone cutters can tilt or 'index' the upper half ( or upper girdle ) facets. This indexing produces different amounts of weight retention from a given piece of rough and produces different optical performance effects. Indexing can also affect crown height and spread ( millimeter footprint versus weight, also called 'weight ratio' ).

 

AGSL discontinued the proportion set based DQD on March 31 of this year.  Now the only available DQD is the performance based version.  Requests from industry members wanting us to define Ideal proportions prompted us to write this article.  Just as some people still like to talk about a fine diamond being a 60-60, so too many people like to ‘hang their hat’ on a range of proportions.  Change can cause fear or anxiety and it’s just human nature to not want to lose a grading system that they were comfortable using.  With today’s technology, it is less accurate, impractical and virtually impossible to try and define a set of Ideal proportions.  The examples in the article convincingly demonstrate this.