#Positions of gems meaning windows

In well-cut gems, most light returns as brilliance (left). If a gem is cut too shallow, light will pass straight through, rather than returning to the eye as brilliance. It is these phenomena which this article will discuss.

#Positions of gems meaning windows

These three color variations result from three different phenomena: brilliance, windows and extinction. Instead (aside from effects due to pleochroism and color zoning), it displays three varying shades of the hue. However, a faceted colored stone does not just display a single uniform color when viewed from above. It is this feature which the cut is intended to enhance. The most striking aspect of a colored stone's beauty is its color. Unlike diamond, most colored stones possess little dispersive power thus the cutting style of a colored gem is designed only for brilliance and scintillation, largely the former rather than the latter. Brilliance is provided mainly by the pavilion facets, which catch the light rays and throw them back to the eye while dispersion results from the prism effect of the crown facets, which split white light into its spectral components scintillation is achieved by breaking large facets up into smaller ones (during cutting) to create a twinkling effect when either the eye, the light or the stone is moved. The stated purpose of a diamond's cutting style is largely threefold: to create, in a symmetrically pleasing but durable manner, a maximum combination of brilliance (return of light), dispersion ('fire'), and scintillation (a twinkling effect). The advent of colored stone grading systems in the past ten years, however, has brought about a reexamination of the exact role that cutting plays in the beauty of gemstones. Of these three, perhaps the most neglected and misunderstood is cut. Gemologists have long recognized that the beauty of colored gemstones results from a complex interaction of three basic features: color, clarity and cut. Diagrams demonstrate that extinction is largely a function of cut. A discussion of brilliance, windows and extinction as they relate to the face-up appearance of colored gemstones.