Quite often the cut of a diamond is confused with its shape. Diamonds are cut into various shapes depending upon the original form of the uncut diamond, which is referred to as “rough.” Whatever the shape, a well-cut diamond is better able to reflect light.

A diamond's ability to reflect light determines its display of fire and brilliance. Diamonds are usually cut with 58 facets, or separate flat surfaces. These facets follow a mathematical formula and are placed at precise angles in relation to each other. This relationship is designed to maximize the amount of light reflected through the diamond and to increase its beauty.

IDEAL

This range is very strict and combines the best in brilliance and fire. Technically, the head of the class.

EXCELLENT

This range is also of great beauty yet slightly more flexible regarding percentages. Many experts prefer the appearance of this range to Ideal.

VERY GOOD

This range is balanced between precise proportions and price considerations. Viewed by many as the best overall value in beauty and price

1. WELL CUT

When a diamond is cut to proper proportions, light is reflected from one facet to another and then dispersed through the top of the stone. Within the Well Cut standards are the Diamonds.com sub categories of Ideal, Excellent, and Very Good.

2. DEEP CUT

When the cut of a diamond is too deep, some light escapes through the opposite side of the pavilion.

3. SHALLOW CUT

When the cut of a diamond is too shallow, light escapes through the pavilion before it can be reflected.

The cut, or proportions, of a diamond is measured in percentages relative to the diameter of its girdle. The girdle diameter of each diamond is always considered 100%. Example: The girdle of a diamond measures 10 millimeters (100%). The table measures 5.6 millimeters. The total depth measurement is 6.1 millimeters. The diamond would be described as having a table of 56% and a depth of 61%. The table and depth percentages are the key to determining good proportions.
 

Think of Ideal, Excellent and Very Good as rings in a bull's eye. These classifications for cut represent an acceptable range for that category. The ranges narrow as you move toward Ideal at the center. Ideal has the narrowest range, with Excellent slightly larger and Very Good the largest. All three of these categories fall within the "well cut" classification. In many cases the visual differences from one classification to the next are so small they may be indiscernible to the naked eye. Science has produced sophisticated machinery that can measure every aspect of a diamond’s proportions. It is this precision that allows such strict standards to be defined. These guidelines give you the ability to not only make a selection regarding cut but to understand the underlying science upon which it is based. In any case a brilliant and scintillating diamond is ultimately the goal.

The Lowest score becomes the overall cut grade. In order to classify each diamond with an overall cut grade the lowest assigned grade for any individual characteristic is always used. For example: If the table percentage falls within Ideal yet the depth percentage is in the Very Good range, the diamond is classified as Very Good.

The proportions are not the same for every shape. Many of the diamond shapes require their own guidelines in order to achieve maximum beauty. Due to the mathematical differences inherent in different shapes, the table and depth guidelines are formulated to maximize fire and brilliance. Although the numbers may be different, the goal is the same: a magnificent display that highlights the individuality and character of each shape.

		TABLE		DEPTH
	ROUND
	ASSCHER EMERALD
	PRINCESS RADIANT
	PEAR MARQUISE
	OVAL
	HEART

GIRDLE

The girdle is the outer edge of a diamond. It usually has a frosted appearance. Many diamonds are also finished with a fully polished or even a faceted girdle. This characteristic does not affect the value of a diamond and is often more a reflection the diamond cutter's preference. The girdle is rated in terms of thickness. Girdle size is generally defined as either Extremely Thin, Very Thin, Thin, Medium, Slightly Thick, Thick, Very Thick, or Extremely Thick. The girdle can also be described as a range of these terms such as Thin to Thick. Avoid the two Extremes. When purchasing a diamond, select one with a girdle that is neither Extremely Thin nor Extremely Thick.

CULET

The culet is the bottom point of the diamond. In many cases this point actually has a very small facet. The culet is referred to in terms that relate to the presence or size of this facet. The culet is generally graded as None or Pointed, Very Small, Small, Medium, Slightly Large, Large, Very Large, and Extremely Large. Smaller is more desirable.

POLISH

This characteristic refers to the finishing or final polishing of the facets, or flat surfaces. Contrary to common belief, diamonds are ground and polished, not chipped away, until they reach their final form. Each facet should be carefully fashioned by the diamond cutter to shine and be free from polishing imperfections. The polish of a diamond is generally defined as either Poor, Fair, Good, Very Good, or Excellent. When purchasing a diamond, select one with a polishing grade of Good or above.

SYMMETRY

This characteristic refers to the alignment and positioning of the facets, or flat surfaces. Each facet should be carefully positioned by the diamond cutter in proper proportion and relationship to the other facets. The alignment of each facet should be sharp and precise; improperly joined facet junctions can make a diamond appear uneven. The symmetry of a diamond is generally defined as either Poor, Fair, Good, Very Good, or Excellent. When purchasing a diamond, select one with a symmetry grade of Good or above.

FLUORESCENCE

This characteristic refers to the diamond’s ability to fluoresce under ultraviolet light. When exposed to UV light, many diamonds will give off a distinctive glowing blue coloration. Although fluorescence may be displayed in various shades, blue is the most common in diamonds. The fluorescence of a diamond is defined by its intensity as either None, Faint, Medium, Strong, or Very Strong. Most of the time fluorescence isn't an issue unless the intensity is Strong or Very Strong. In the very high colors D, E, and F, Strong fluorescence is considered less desirable. Ironically, in slightly lower colors of J and below, Strong fluorescence is desirable.