How to Buy a Diamond

Of the 4Cs - Cut, Color, Clarity, and Carat - cut refers to the brilliance of a diamond. More specifically, it addresses the number, placement, angling and shape of the facets to create a polished diamond. The facets function as prisms, capturing and reflecting light inside the diamond. A well cut, well proportioned stone displays maximum brilliance (liveliness or white-light sparkle) and fire (variety and intensity of rainbow colors dispersed). It simply comes alive.

Simply click on the three different parts of the diamond to learn more about each one.

Crown	The part of the diamond above the girdle
Table	the large facet that caps the crown of a stone
Girdle	The outer edge of the diamond, usually the portion that is grasped by the setting. It is the dividing line between the crown and the pavilion.
Pavilion	The part of the diamond below the girdle.
Culet	The small facet parallel to the girdle, at the bottom of the stone.

The cut, also called the diamond's "make," is extraordinarily important because it has the greatest single influence on the brilliance of the stone. The quality of a stone's cut is primarily determined by the height of the crown relative to the depth of the pavilion and the width of the table. If a stone is cut too shallow - or too deep - the light that enters it from above will leak out the bottom and sides of the stone, causing the stone to look dull or dark.

An exacting talent

Of the four qualities that define a diamond's value, the cut is the only one determined by a human being. A skilled diamond cutter realizes the rough diamond's potential. He cuts and facets the crystal to reflect the maximum amount of light inside the stone and back through the top of the diamond. His objective is to produce a perfectly symmetrical stone whose right and left sides are mirror images of each other.

At the same time, he has to find the optimal balance between yielding the most diamond weight and creating the best proportioned cut. One reason why higher grades of cut are so much more costly is because more diamond was sacrificed to create them. That's also why a well proportioned one-carat diamond may be worth twice as much as a poorly proportioned larger diamond that lacks fire and brilliance.

In search of the "ideal"

For centuries, diamond cutting experts have pondered what combination of proportions creates the optimal balance of brilliance, scintillation and dispersion (the diamond's sparkle and fire).

The 58-facet model developed in 1919 by master gem cutter and mathematician Marcel Tolkowsky has provided a foundation for today's most widely accepted proportions. However, while Tolkowsky's model dictated precise proportions for table diameter, crown height, pavilion depth, crown angle and pavilion angle, many grading labs and diamond sellers today offer a more liberal interpretation. The market itself dictates a wider range of acceptable proportions.

In fact, the Gemological Institute of America (GIA), the world's leading gemological authority, actually advises against using the term "ideal" cut. Why? Because the GIA has demonstrated that literally thousands of variations on these proportions can maximize the different optical characteristics displayed by a diamond. As long as the diamond's proportions fall within the acceptable range of tolerances (and Shane Co. searches the world's markets for the finest cuts), you can be assured of buying a stone that is well made. Furthermore, you could view two stones with vastly different cut proportions, and be hard-pressed to determine which stone is more beautiful.

Well Cut

Light is reflected from one facet to another and then dispersed through the top of the stone.

Too Deep

Too Shallow

For appearance's sake