Diamond Grading

In this video Paul Slegers and Lieve Peters of Infinity diamonds are inspecting diamonds after the rough has been sawn into two pieces. Most of the narrative is from John Pollard as he does an excellent job of giving us an overfview of what is happening.

Historically ‘blue white’ fluorescent top coloured (D to F on the GIA colour grading scale) diamonds were once priced around 10% more than non fluorescent diamonds. Today D to F coloured blue fluorescent diamonds are usually discounted on wholesale markets. There are two main technical reasons why fluorescent diamonds would be discounted. The diamond’s body colour may have been ‘over-graded’ or its transparency may have been impaired.

I have been in the jewelry business since 1970 when I bought my first gemstone for a girlfriend in Rio de Janeiro, Brazil. Within days I was buying & selling gems and my lifelong love affair and study of gemology was started. I graduated from the Gemological Institute of America in 1975, and have been a proud member of the trade ever since.

What the report doesn’t show

 

To the naked eye a D Flawless diamond can appear identical to an F VS diamond if each has been cut the same way.  Alternately, less than one degree of variation in two diamonds’ facet measurements can make a noticeable difference in appearance - yet both could be issued the same cut grade from a given lab.

Recently, I had the opportunity to examine two very similar diamonds, one cut to near Tolkowsky ideal AGS0 specifications and one cut to near what dealers refer to as 60/60 make. 60/60 refers to 60% table, 60% depth. Diamond dealers would consider both of these cut styles as very good cutting, but the ideal spec stone has a distinct advantage in the Internet marketplace. It got me thinking about why that is the case. Both of these diamond looked very good and not all that different than one another. Why does one, the ideal cut, hold such an advantage?