It's all about diamonds,
diamond grading and diamond prices

| tutorial | cut adviser | ideal-scope | price stats | forum | appraisers | vendors | tips | faq | about 

HCA - Defining the Beauty and Desirability of Round Brilliant Diamonds

Scintillation

The scores from zero to 2 were given using a similar comparison method as used for brilliance and fire. You can clearly see the pleasing star patterns in the chart in the GIA brilliance review section.
 
Unlike fire and brilliance (the more, the better) the ideal amount of scintillation is in the eye of the beholder; the observer is an important variable. A person with excellent eyesight may examine diamonds from a distance of 8 inches (20cm) whereas a viewer with poor eyesight may hold a diamond at arms length to focus on it (common with advancing age). A person with poor eyesight may find a Tolkowsky proportioned stone has insufficient contrast¹. She may find a diamond with shallower crown and pavilion angles and shorter pavilion half facets more scintillating.
 
The GIA’s ‘Modeling Brilliance’ article chose to use an observer free illumination and images and photographs displayed in Figure 2 show the effect of no scintillation.
 
Another variable in considerations of scintillation is observer appearance. A bald fair skinned person in white clothing viewing a diamond will observe less scintillation than a dark person wearing a big black hat and a black suit. The latter will see more darkness in diamonds.
 
The bow tie in a marquise is the ‘nail head’ or observer reflection (or that of a camera or microscope lens). A nail head results when pavilion angle is greater than 43.5° causing a table-to-table reflection of the viewers own head (Harding 1975). A view of the same marquise (or a nail head) through a peephole in a sheet of white paper magically turns the bow tie white.

Figure 16. Comparative scintillation scores estimated for each diamond on grids for crown and pavilion angles shown and for table sizes of 53% to 65% in 1% increments.
 
 
¹ Many people prefer single cut diamonds below 0.02cts because to their eyes they scintillate more.

<< Fire or Dispersion  |  Spread >>