A Diamond's Finish and Fluorescence

A diamond’s finish is the quality of its polish and the symmetry.   When a diamond’s cut, polish, and symmetry are all graded at “Excellent” level, we call this 3EX. 

Polish and Symmetry

“Symmetry” is a term used in the diamond industry to refer to the degree of precision by which the various facets of a diamond align and intersect one another. A diamond's symmetry can also be evaluated by assessing additional and misshapen facets; culets and tables that may be off centre, and girdles with an uneven or wavy finish. A diamond suspected to be unsymmetrical may redirect light differently to one with uniform symmetry. Poor cut and symmetry can cause light to be refracted and reflected at wrong angles, thus reducing a diamond's brilliance. 

“Polish” is the term used by gemmologists to refer to the measurable and aesthetic smoothness of a diamond's facets when analysed at 10x magnification. During the cutting and polishing process, small fragments of the stone are sometimes dislodged by the polishing wheel, and dragged along the surface of the diamond causing minor surface defects. Depending upon the severity of this surface damage, the patterns of light created when light rays infiltrate and exit the diamond may be affected. 

Both polish and symmetry are taken into consideration when a diamond's cut is graded during GIA analysis. If the polish and symmetry have a detrimental impact upon a diamond's brilliance and fire, the cut grade will have been altered to account for this. From an aesthetic point of view, this means that if the cut grade is excellent, you won't necessarily need to worry if grades assigned for polish and symmetry are lower than excellent.

3EX – An Overview

3EX diamonds (Excellent Cut, Excellent Symmetry, and Excellent Polish) are becoming more popular these days, since it speaks the high quality of a diamond’s finish.  However, it must be noted that a 3EX diamond doesn’t necessarily give off better visual appearance to the naked eyes. In our experience, the “Very Good” grade assigned to diamonds for polish and symmetry is usually an adequate guarantee of superb brightness, fire and scintillation, as long as the “Cut” is graded as “Excellent”.  So, for pure visual impact, we recommend you forfeit the 3EX rule in favour of a higher Carat, Clarity, or Colour Grade.  These three 3C’s are of significantly greater importance than 3EX, since combined, they create far more of aesthetic beauty than a superior polish and symmetry.  However, it must be noted that 3EX has become ever more popular, and if you are buying the diamond with the consideration of future resell or gift giving purposes, then you should take 3EX more seriously.  

Fluorescence

“Fluorescence” refers to the visible light emitted from a diamond when exposed to ultraviolet (UV) rays.

The impact of diamond fluorescence on aesthetic quality is a hotly contested topic among experts. So much so, that the GIA conducted a study back in 1997 to assess the impact of fluorescence on diamond appearance. Enlisting the help of a panel of expert gemmologists and consumers, the GIA ran a series of tests in controlled lighting conditions, and asked subjects to record their answers separately. The results of the study affirmed this; fluorescence had very little affect upon the appearance of most diamonds. In actual fact, diamonds with a colour grade of H or below appeared to be whiter and brighter under UV light. Fluorescence is a characteristic largely borne of taste. Some individuals actually prefer diamonds with a mid to strong fluorescence.

Occasionally, fluorescence can negatively impact the appearance of a diamond. According to the GIA this is quite rare, evident in less than 0.2% of fluorescent diamonds submitted for grading. The effect is most often seen with diamonds that range from Strong to Very Strong on the intensity scale, and may appear cloudy, hazy, or oil-like under normal lighting conditions.