DIAMOND CUT
Cut refers not to a diamond's shape (e.g. round, oval, pear, etc.) but to a diamond's proportions, symmetry and polish. The beauty of a diamond depends more on cut than any other factor. Though extremely difficult to analyze and quantify, diamond cut has three primary effects on appearance: brilliance (the brightness created by the combination of all the white light reflections from the surface and the inside of a polished diamond), fire (the dispersion of light into the colors of the visible spectrum, seen as flashes of color), and scintillation (the flashes of light and dark, or sparkle, when a diamond or light source is moved).
When a diamond is fashioned from a rough stone, the cutter must balance optimal cut (and therefore appearance) against maximum yield (cutting the diamond to maintain as much carat weight from the rough stone as possible). Because many customers are willing to pay more for a larger, fair-cut cut diamond than for a slightly smaller, well-cut diamond, there is pressure on the cutter to sacrifice appearance for weight. This is why the Cut grade is so important; it allows the purchaser to identify those stones that were cut Fair to Poor in an effort to gain carat weight.
Diamond Cut
At left, the same rough stone (shown in blue) can yield one of two potential diamonds:
A too-deep cut diamond (orange) would yield a significantly larger diamond, earning the diamond cutter a larger profit on his investment.
A smaller, well cut diamond (white) may sell for less in total than the larger diamond, but it will command a higher price-per-carat not only because of its superior appearance, but also due to decreased yield from the rough stone (which therefore makes the diamond more expensive to create).
Questions about cut or other aspects of a diamond? Ask a diamond consultant for answers. A consultant will answer any questions you have, and if you like, search for diamonds on your behalf that match your criteria. Chat online, or call 1-888-658-6372 now.
DIAMOND CUT PROPORTIONS
Diamond proportion refers to the relationship between the size, shape, and angle of each facet of a diamond. A wide range of combinations are possible, ultimately determining the diamond's interaction with light.
When light strikes a diamond, approximately 20% immediately reflects off the surface (as glare). Of the 80% that enters, a portion will escape through the bottom of the diamond (where the observer cannot appreciate it). A well proportioned diamond will have each facet properly placed and angled so as to maximize the amount of light that reflects back out of the crown (top) of the diamond, to the eye of the observer. This reflected light is perceived as scintillation, fire and brilliance.
In the diagram below, three common light patterns are shown. When light meets any facet of a diamond, it will either reflect (bounce back) or refract (bend while passing through the facet). The angle that the light hits the facet determines whether the majority of light reflects or refracts, which is why cut is so important.
Shallow Diamond Cut
If the diamond cut is too shallow, entering light strikes the pavilion facet at a low angle and passes through the facet (refracts), escaping through the bottom of the diamond.
Deep Diamond Cut
If the diamond cut is too deep, entering light strikes the first pavilion facet at an angle sharp enough to reflect to the second pavilion. But the light strikes the second pavilion at too low an angle, causing the light to refract (pass through the facet), escaping through the bottom of the diamond.
Correct Diamond Cut
In a well cut diamond, the light strikes each pavilion facet at an angle which allows most of the light to reflect back to the crown (top). As it passes through the crown facets at a low angle, the light refracts upon exit. In this case, refraction is a good thing, as the bent light travels to the observer's eye and is perceived as a lively fire.
DIAMOND DEPTH %
Depth refers to the distance between the culet and the table when the diamond is viewed from the side. Diamond depth is expressed in millimeters, and is given as the third number under "measurements" for every Lumera Diamond (the first two numbers are length and width).
The depth % of a diamond is calculated by dividing the depth by the width of the diamond. So, if a diamond is 3 mm in depth, and 4.5 mm in width, its depth % is 66.7. The lower the depth %, the larger a diamond of a given carat weight will appear (since most of the diamond's size is in its width vs. in its depth).
DIAMOND TABLE %
The table % of a diamond is calculated by dividing the width of the table facet by the width of the diamond. So, if the table facet is 3 mm wide, and the diamond is 4.5 mm wide, its table % is 66.7.
A note of caution:
A diamond should not be chosen or rejected based solely on depth % or table %. Because the overall Cut grade already incorporates both factors, it should be used as the primary determinant when choosing a diamond. When comparing two diamonds of equal Cut grade, depth % and table % can then be used as further refinements, especially (in the case of depth %) if one is concerned about how large the diamond will appear.
DIAMOND PROPORTION DIAGRAM
GIA Diamond Proportion Diagram
GIA Diamond Proportion Diagram
Every Lumera Diamond comes with a GIA Grading Report or Dossier certificate, most of which include a proportion diagram. The proportion diagram is a graphic representation of the diamond's actual proportions.
The proportion diagram shows the diamond's girdle size, culet size, table and depth percentages, as well as other measurements, such as the crown and pavillion angles.
Each angle and dimension is measured electronically using a light scanner. The proportion diagram is a "fingerprint" of your diamond.