Diamond Size and Weight Buying Guide

Faulty diamonds.

Many errors that effect the appearance and value of a diamond can occur in cutting. Remember that some diamond's cutting faults will make a stone more vulnerable to breakage. We recommend avoiding such stones unless they can be protected by the setting.

There are several cutting faults to watch for in round diamonds. First, look carefully for a sloping table or a table that is not nearly perfectly perpendicular to the point of culet.

Second, the diamond culet can frequently be the source of a problem. It can be chipped or broken, open or large (almost all modern cut diamonds have culet that come near to a point), or it can be missing alike.
Third, repairs to chipped areas can result in misaligned facets, which destroy the stone's symmetry.

Sometimes. too, as a result of repair, an extra facet will be formed, often in the crown facets, but also on ot just below the girdle. These extra facets may slowly affect the diamond's brilliance.

Girdle Faults

The girdle is often the source of faults in a diamond. Bearded or fringed girdles are common. A fringed girdle exhibits small radial cracks penetrating into stone; these can result from a careless or inexperienced cutter. A bearded girdle is similar but not as pronounced a fault and can be easily repaired by re-polishing, with minor loss in diamond weight.
The relative thickness of girdle is very important because it can affect the durability as well as the beauty of the stone. Any girdle can be nicked or chipped in the course of wear, or by careless handling, but if the girdle is too thin it will chip easily. Some chips can be easily removed by re-polishing, with minimal diamond weight loss. If there are numerous chips, the entire girdle can be re-polished. Chips or nicks in the girdle are often hidden under the prongs or understood by the setting.
If the girdle is too thick, the stone may look smaller because a disproportionate amount of its weight will be in the girdle itself; such stones, for their weight, will be smaller in diameter than other stones of comparable weight.

The gradations of girdle thickness:

Extremely thin



Slightly thick

Extremely Thick

The girdle can also be wavy, rough, or entirely, out of round.
A natural may not be a fault. It's actually a piece of the natural surface of the diamond crystal. In cutting, a cutter may decide to leave part of the "natural" rough surface in order to get as large a diamond as possible from the rough stone. If this natural is no thicker than the thickness of the girdle and does not distort the circumference of the stone, most dealers consider it a minor defect at worst; it it extends into the crown or pavilion of the stone, it is a more serious fault.
Sometimes, if the natural is somewhat large but slowly below the girdle, it will be polished off. This produces an extra facet.

Other Popular shapes

Unlike round diamonds, "fancy" shapes, all shapes other than round, have no set formulas, so evaluating the make of a fancy is more subjective. Table and depth percentage can vary widely among individual stones of the same shape, each producing a beautiful stone. Personal taste also varies with regard to what constitutes the "ideal" for shapes other than round. Nonetheless, there are certain visual indicators of good or poor proportioning, such as the "bow tie" effect, which even the amateur can learn to spot. There are recommended ratios for overall shape and symmetry, but a preferred shape is a largely a personal matter. Ranges for what is "acceptable" or "unacceptable" have been developed. As you gain experience looking at specific shapes, you will be able to spot faults, and begin to determine what is within an "acceptable" range. Moderate deviation will not significantly affect the beauty or value of a stone; however, extreme deviations can seriously reduce a stone's beauty and value.

Cutting faults in popular fancy shapes

One of the most obvious indicators of poor proportioning in fancy shapes is the bow tie, or butterfly effect, a darkened area across the center or widest part of the stone, depending upon the cut. The bow tie is most commonly seen in the pear shape or marquise shape but may exist in any fancy shape diamonds. Virtually all fancy shapes cut today will exhibit some minimal bow tie effect. Nonetheless, the presence or absence of a bow tie is an indicator of proper proportioning. In poor proportional stones there is a pronounced bow tie; the more pronounced, the poorer the proportioning. The less pronounced the bow tie, the better the proportioning. The degree to which the bow tie is evident is the first indicator of a good or poor make. A diamond with a pronounced bow tie should sell for much less than one without.

As with the brilliant cut diamond, fancy shapes can also be cut too broad or too narrow; and the pavilion can be too deep or too shallow.
Personal taste will always play a role in fancy shapes, some prefer a narrow pear shape, for example, while others might prefer a fatter pear. Whatever the shape you are considering, you must ask yourself whether or not you find the stone exciting. Does it have a pleasant personality? Does it exhibit good brilliance and fire? Is the entire stone brilliant, or are there "dead" spots? Are there any cutting faults that might make it more susceptible to chipping? Then you must make the choice.

New shapes create excitation

Today we can choose from many diamond shapes and diamond cuts, ranging from the classics diamond shapes:





Emerald-cut, and


To new diamond shapes that appear as cutters continue to experiment with novel looks. Here are some of the most exciting:


A rectangular or square brilliant cut, this shape is perfect for the person who likes the shape of an emerald-cut but want more sparkle. The starburst radiant is a variation of the standard radiant, and exhibits a slightly different personality.


A square brilliant cut which is ideal for bezel and channel settings, or ant setting in which you want the stone to be flush with the mounting. The quadrillion was the first trademark "princess" and is cut to unique specifications which some believe creates the most beautiful of square brilliant cuts, and which demands a slightly higher price than others of this general types.

144 Facet

This patented cut produces a diamond with 144 facets rather than a diamond with 58 facets, giving it unsurpassed brilliance and fire. An important feature of the 144 Facet is the girdle, which is more resistant to chipping than girdles produced by many other cuts. The 144 Facet is an expensive cut, comparable in cost to an "ideal" make diamond.

Dream a Royal cuts

These cuts are a good choice for anyone who wants a large look on a limited budget. They are "thin" cuts, but unlike "spread" or "swindle" diamonds, which are usually lifeless, extra faceting and precision cutting help to produce unusual brilliance for their depth. A dream cut marquise (or, similarly, the "Duchess") will look much larger than a traditional marquise of the same weight. These cuts are available in shapes resembling the marquise, pear, and oval.


Popular shape for use as a center stone, or for side stones, this triangular brilliant cut is also a thin cut, giving a large look for it weight. Extra facets and precision cutting produce high brilliance. When flanking either side of another diamond, trilliants produce a much larger diamond look, overall.

In addition to the new cuts discussed above, one of the newest cutting innovations is the brilliant cut baguette, such as the Princette (TM) and Bagillion (TM). They occur in a "straight" and "tapered" shape. These have gained popularity because they have greater brilliance than traditional baguettes. They can be used to flank diamonds or other stone in traditional settings, or used in very contemporary jewelry design with straight, clean lines.

Early cuts enjoy renewed popularity

Interest in antique and period jewelry is growing rapidly and, as it does, the diamonds that adorn them are arousing renewed attention and gaining new respect. The way a diamond is cut is often one of the clues to the age of a piece. Older diamonds can be replaced or re-cut to modern proportions, but replacing or re-cutting stones mounted in antique or period pieces could adversely affect the value of the jewelry. To preserve the integrity of the piece, antique and period jewelry connoisseurs want "original" stones, or, if stones have been replaced, at least stones cut in the manner typical of the period. The market is becoming increasingly strong for diamonds with older cuts, and pieces are also strengthening.

As these early cut diamonds receive more and more attention, a growing number of people are beginning to appreciate them for their distinct beauty and personality, and for the romance that companies them. The romantic element, combined with a cost that is more attractive than new diamonds, is also making them an increasingly popular choice for engagement rings.

Some of the most popular early diamond cuts are: the table cut, the rose cut, the "old-mine" cut, the "old European" cut (Prior to 1919, when America began to emerge as an important diamond cutting center, most diamonds were cut in Europe. Most "Old European" diamonds were cut prior to the first quarter of the 29th century).

Table cut

The table cut illustrate man's earliest cutting effort. By placing the point of a diamond crystal against a turning wheel that held another diamond, the point could be worn down, creating a squarish, flat surface that resembled a table top. Today we still call the flat facet on the very top of the stone the table facet.

Rose cut

The rose cut is a sixteenth century cut, usually with a flat base and facets radiating from the center in multiples of six, creating the appearance of an opening rose-bud. The rose cut shows in round, pear, and oval shapes.

Old-mine cut

The old-mine cut was a precursor to the modern round. This cut had a squarish or "cushion" shape (a rounded square or rectangular) and and more facets than today's modern 58 facet diamond. Proportions followed the diamond crystal, so the crown is higher and pavilion deeper than modern stones. The table is very small, and the culet is very large and easily seen from the top (resembling a "hole" in the diamond). These lack the brilliance of modern stones, but often exhibit magnificent fire. Old-mine cut diamonds are also seen in pear and oval shape.

Old European cut

Appearing in the mid 1800s, the old European cut is similar to the old-mine cut diamonds, but is round rather than squarish, with 58 facets. The crown is higher than modern cuts, but not as high as in the old-mine cut; it has a deep pavilion, but not as deep as old-mines. The culet is still "open 'but smaller than old-mines.

Old cuts can be very beautiful. The intense "fire" exhibited by some old-mine and old-European cut can have tremendous allure. By today's standards, however, they lack brilliance, and a very large culet may detract from the stone's beauty.

Are diamonds with old cuts valuable?

Old-mine cut and old-European cut diamonds are normally evaluated by comparison to modern-cut stones. Value is usually determined by estimating the color, clarity, and the weight the stone would retain if it were re-cut to modern proportions.

It is not suggested to re-cut old diamonds if they are in their original mountings. The overall integrity of the piece, and value, would have been adversely affected by doing so.

If the setting has no special merit, the decision must be an individual one, based on whether or not the stone appeals to you. As we have said, some older cuts are very lovely, while others may look heavy, dull, or lifeless. An unattractive older cut may have equal, or greater, value because of the improved make. In addition, re-cutting can sometimes improve the clarity grade of an older stone.

A word about re-cutting diamonds.

There are many fine diamond cutters in the United States, New York City is one of the most important diamond cutting centers in the world for top quality diamonds, and many diamonds can be greatly improved by re-cutting. The cost is surprisingly low when one considers the benefit to the stone, and effect of re-cutting on the diamond's beauty and value (sometimes the clarity grade is also improved).

If you have an old-cut diamond which you do not care for, or a damaged diamond, your jeweler can consult with a diamond cutter, or refer you to one, to determine whether or not your stone can be improved by re-cutting and, if so, what risks and costs might be involved.

A Knowledgeable jeweler can help you decide whether or not a diamond should be re-cut, make arrangement for you, and help assure you that you have received the same stone back. For your own comfort and security, as well as the cutter's, we always recommend that prior to having a stone re-cut you obtain a diamond grading report or thorough appraisal so that you have a point of reference when the stone is returned.

To what extent does cutting and proportioning affect value in modern diamonds?

Excellent cut and proportioned stones cost significantly more per carat than those that are not cut well.

Remember: The value of two diamonds with the same weight, color, and clarity can differ dramatically because of differences in cutting.