Diamonds - The 4 C's

The 4 C's - Cut, Clarity, Color & Carat Weight

Cut
Cut - a short word with a lot of meaning.
Not all jewelers know what they mean when they talk about "cut" or that the word can be used quite ambiguously to mean at least two different things.
Cut can be use to mean:-

Color
Color is one of the 4 C's which determine the price of a diamond.
De Beers make diamond promotional material available to every jeweler in the form of leaflets, & and more, and yet there is still much confusion about the role of Color as a quality factor in diamonds.

Are Diamonds White?
It is commonly believed that most diamonds are white, although strictly we should say Colorless. This is incorrect, most diamonds actually show at least a trace of body Color, and many are quite deeply Colored. To their credit, De Beers do point out that most diamonds are faintly yellow, however many diamonds are faintly brown, green, gray, or other Colors.

Is White Best?
It's really a matter of personal preference. Because De Beers promote white as being the most expensive Color for diamonds, most people blindly believe that white is best, and some even believe that yellow is bad! While it is generally true that Colorless diamonds are more expensive than tinted diamonds, it is not true that they are better, just that there is a difference. Many distinctly yellow diamonds are very bright, sparkling, attractive and desirable.

What About Fancy Colors?
Intensely Colored diamonds are very rare, and are also very attractive and desirable. Because they are not actively marketed, certainly not by De Beers, knowledge levels and demand for them is relatively low. Even so, they command high prices, often much more than Colorless diamonds. These intensely Colored diamonds are known as "Fancy" Colored or "Fancies". They exist in yellow, greens, brown, red, orange, blue, and other Colors. Also some diamonds with faint or pale Coloring are rare and desirable, these Colors include pink and blue.
It is our own opinion that the main reason De Beers do not promote Color as a positive attribute in diamonds is that most diamonds are near Colorless, and fancy Colors are so very rare. Promotion of Color would risk educating consumers to appreciate Colored stones, and this may divert demand away from diamonds, and in the direction of ruby, sapphire, emerald, amethyst, opals, and other naturally Colored gemstones.
Some Colored diamonds can be treated by irradiation and heat to change or intensify their Color. These are termed as treated fancies, and can be bought for lower prices than natural fancies.
Naturally we have a page about Colored diamonds.

What About Fire?
The ability of a diamond to refract and disperse white light into all the rainbow Colors of the spectrum is sometimes called "fire", and it is one of the desirable qualities of diamonds. Well polished diamonds sparkle and flash with lots of fire. It is easy to confuse this aspect of Color with the "body" Color of a diamond. So what do we mean by "body" Color?

What Is "Body" Color"
Body Color is simply the Color seen when white light travels through the diamond without being dispersed, rather than the multi-Colored flashes caused by dispersion. Body Color is best judged by viewing the stone through the side rather than through the top. It is the Color which the diamond would appear if it were not facetted, and is the stone's true Color. The "fire" actually confuses the eye, and makes it almost impossible to judge the body Color. The term "body Color" is only used to emphasize which aspect of Color is intended, when the word Color is used, it normally is understood to mean body Color.

Color Grading
In recent years, a de-facto international standard grading system has evolved, based on the standards of the G.I.A., the Gemological Institute of America. Terminology differs in European standards, but the grades are identical.
The following table shows the GIA, traditional UK, and CIBJO Color scales, together with our graphical representation. We have assumed that your computers video card can display at least 256 shades of Color. Obviously this chart may appear different on different monitors, therefore it is advisable to treat our Color column in the table as only a general guide rather than as an exact rendition of any particular Color.

Shape would be a more accurate word rather than "cut" when we are talking about whether a diamond is round, square, oblong, or whatever. Some round shapes may have different arrangements or numbers of facets.

* Round
The most popular "shape" of diamond remains the round shape, for very sound reasons. Round shaped diamonds come in several varieties:-
o Modern Brilliant Cut
Often known as the brilliant, round, round brilliant, or "brill.". Has 58 facets, including the table and culet.
o Eight Cut or Single Cut
Often used for very small diamonds, under 1 or 2 "points". These only have eight facets on the crown, eight on the pavilion, plus the table and culet, making 18 in total.
o Old Cut or Early Modern Brilliant
An older, less precisely cut version of the modern brilliant cut.
o Swiss Cut
Halfway between a brilliant and an eight cut, with 34 facets in total.
o Rose Cut
Most rose cut diamonds are round, but some may look triangular, or have straight edges. Rose cuts look like diamonds which have been cut upside-down, they rise to a point at the top, and are often flat at the base.
o Chips or Chippings
Chips should only be used to refer to deep fried potato fingers, french fries or pommes frites. To the French, chips mean potato crisps. Any jeweler who refers to chips or chippings meaning small diamonds is not a jeweler Technically, we suppose that broken pieces of unpolished diamond could be set into jeweler, but we have yet to see it. Only refer to diamonds as chips if you don't mind folk realizing that you don't know your crown from your culet!
* Square
The square shaped diamond is really only a special case of the oblong shape.
* Oblong or Baguette
Most oblong or rectangular diamonds are "step" cut, which means that their facets have been cut in steps, parallel to the edges, in the manner of a pyramid with its top chopped off. Long thin oblongs are often known as baguettes. Tapered baguettes also exist.
* Emerald or Octagon
This is another "step" cut, but with the four corners mitered. This is done largely to protect the stone, as any sharp points are vulnerable to getting chipped.
* Oval
Most oval diamonds are like a squashed round brilliant. Because their depth to diameter ratio varies, they can never be a "perfect" proportion, and therefore lose some brilliance when compared with a round diamond. Actually most "round" diamonds are very slightly off-round.
* Marquise
Marquise or navette shape is like a long oval which has been stretched out to a point at each end. Similar comments apply as to the oval.
* Triangle
Not a popular shape. It is normally a variation of the square cut, in that its facets are step cut, but some triangle shapes are a modification of the round brilliant cut.
* Pear
One half oval, and the other half marquise.
* Heart
Pear shape with a notch cut into the top.
* Princess
A relatively new shape, oblong, usually square or almost square, but with a modified brilliant cut arrangement of facets instead of a step cut. This produces a much more brilliant and sparkly diamond than a traditional step cut square or oblong. It is not as successful for baguette shapes (long and thin).
* Radiant
This is a hybrid cut, a cross between a princess cut and an emerald cut. It combines the best features of the round brilliant cut, the square shape of the princess or square baguette cut, and the cut corners of the emerald cut. Like the princess cut, it is normally used for near-square stones rather than oblong ones.
* Kite or Diamond Shape
A fancy shape which resembles a kite, or the sectional profile of a diamond viewed from the side.

Proportion and Polish
"Rough" diamonds, as they are mined or found, do actually look very rough, and need to be enhanced by shaping them using various methods, the process often known as cutting or polishing.
In practice, there are many different parts to creating a finished, ready-to-set, diamond from a piece of "rough".
Cleaving is literally to cleave or part a stone along natural grain boundaries, in the way one might chop a piece of wood along its grain, but not across the grain.
Sawing or cutting is performed across the grain of a stone, and is done using a thin toothless circular saw blade which is impregnated with diamond dust. It is the diamond grit or dust which performs the cutting action.
Polishing involves grinding surplus diamond away to leave the facets. Most of the work done, and weight removed from a rough diamond is done in this way.
Bruting involves rubbing the rough diamond against another by rotating it, to make the circular shape of the finished stone. This is performed before the grinding operation.
Polish can be used to mean the actual quality of the polish which has been achieved on each of the facets.
Proportion also has multiple meanings.
The most important proportion and the easiest to ascertain is the ratio between the depth of the stone and its diameter. Ideally this should be about 58.5%, but a few percent either side of this is perfectly acceptable.
The ratio between the height of the crown and that of the pavilion is also important. The length of the pavilion facets, the size and shape of the various crown facets, the size of the table and the culet all contribute to the overall perfection or quality of the "cut."

Why Proportion Matters
Well proportioned stones reflect more light, and therefore often appear whiter and brighter than poorly proportioned stones. This can make a well cut diamond look 2 or 3 Color grades better than it actually is. Similarly, diamonds in perfect proportion may also look better than other diamonds of higher clarity, but which are not as well cut.
Diamonds which "spread" more than their weight often appeal to the less informed who believe, naively, that they are getting something for nothing. A spread stone will lack brilliance and sparkle compared with a perfectly proportioned stone. (By spread, we mean that the diameter is too great in relation to the depth of the stone, which is the same as saying that the diamond is too shallow.)

The Dealer's Cut
This often has more bearing on the price than any other meaning of "cut", and sometimes more effect than all the other 3 C's put together!

Most people would find it difficult to differentiate between diamonds in the first four Color grades, D, E, F and G, even when unmounted. Mounted diamonds of these grades, and also H and I appear Colorless. The ability to notice any Color in these grades will vary with the Color perception of the individual.
Small mounted diamonds down to J and K Color will usually also appear Colorless except under careful inspection, and then only by those with good Color perception. Slight Color may be visible in larger stones
Lower Color grades will show increasingly noticeable Color, although well proportioned stones may appear lighter viewed from above, when mounted, than their body Color would suggest.

Standard scales do not yet extend to brownish diamonds, or diamonds of other Colors.

Clarity
Clarity is possibly the most important of the factors affecting the quality and price of any diamond. Diamonds of all colors can be vary attractive. Diamonds of all different cuts look good, and not many diamonds are very badly proportioned.
Extremes of clarity can produce a brilliant magnificent diamond, or a dead, dull, and lifeless stone. Clarity is also sometimes called purity. The fact that clarity is also sometimes called quality shows the importance of this factor.
Clarity literally means "clearness" rather than lack of inclusions, and refers to the diamond's ability to allow the free passage of light without obstruction or absorption. Any inclusions, cleavages, cracks, or other natural features inside or defects on the surface will stop light from passing through the stone.

What Are Inclusions?
Geologically, an inclusion is "a solid fragment, liquid globule, or pocket of gas enclosed in a mineral or rock."
In gemology, this definition is usually extended to include any other feature of the gemstone which impedes the free passage of light through the stone. This includes changes in crystal growth direction (e.g. twinning), and external features, such as fissures which run from the surface into the stone, naats , trigons, and zones of color absorption (e.g. the very common color banding seen in sapphire).

Are All Inclusions Visible?
No, not all inclusions are visible either with the naked eye, or under the standard 10 times magnification used by gemologists. Many consumers believe that inclusions are things which are visible to the naked eye, and that if no inclusions can be seen, then the stone is perfect. Some stones contain many areas of "twinning", where the growth direction of the crystal has changed during its formation, and these areas can absorb or refract light in such a manner as to reduce the brilliance of the stone. Other stones contain large numbers of small inclusions, some visible under 10x magnification, others not, because they are too small. These clouds of microscopic inclusions can reduce the passage of light through a stone so severely that the stone looks "dead", with no brilliance or fire whatsoever. Such stones usually have a slightly cloudy look to the naked eye.

What Are Carbon Spots?
A common belief, shared by some jeweler shop staff, is that any black marks visible in diamonds are composed of carbon. Diamonds are composed purely of carbon. While it is possible that some inclusions may be of graphite, the commonest form of carbon, or amorphous carbon, such inclusions are quite rare. Dark inclusions in diamond can include other diamonds, olivine, garnet, diopside, pyrrhotite, pentlandite, pyrite, ilmenite, rutile, silica, bronzite, spinel, serpentine, biotite, phlogopite, chlorite, calcite, haematite, goethite, and iron oxides.

Grading Standards
In recent decades, the GIA, Gemological Institute of America, has influenced other gemstone grading bodies, such as CIBJO, throughout the world, and most countries now use the same standards as the GIA for diamond clarity, so that the GIA scale has become virtually an international standard. There still remain vast differences between commercial grading and laboratory grading.
De Beers supply leaflets and showcards for diamond clarity grading, but as their aim is undoubtedly to increase demand for higher quality diamonds at higher prices, the De Beers charts contain some distortion. They typically graphically represent the higher grade bands as wider than the lower grades, whereas in reality it should be the other way round, and the grades below P3 are not even mentioned, as though they do not exist.
We present the following table of diamond clarity grades:-

Carat Weight

Does Size Matter?
Carat weight is not a factor which denotes diamond quality. It purely denotes the size of a diamond, by its weight. Obviously it also affects the value or price of a diamond, because consumers tend to prefer bigger rather than smaller diamonds. Large diamonds are also rarer than small diamonds. Because there is higher demand and lower supply for large diamonds, they command higher prices.
Often people talk about the size of diamonds. Size in this context really means weight, as large diamonds will normally weigh more than small ones.

What is a Carat?
Historically the carat is supposed to have been derived from the weight of locust bean or carob bean seeds, from the Greek Keraton. Until earlier this century, there were at least two different standards for the carat. In 1914, the carat, or metric carat as it was known, was defined as 1/5th of a gram.
It is not always easy to establish the weight of a mounted diamond, it would need to be removed from its mount, and then reset, which always involves some slight risk, not to mention time and expense.
For round diamonds it is fairly easy to estimate their weight by measuring their diameter and, preferably, their depth. If this is done accurately, the weight can be estimated within a fine tolerance (about 1 or 2 %). If the depth cannot be measured, the weight can still be estimated from the diameter, but with less precision.
For diamonds of other shapes, it is more difficult to estimate the weight, but specialized diamond gauges such as the Leverage gauge come with a booklet of conversion tables, and instructions (albeit rather unmathematical) for calculating diamond weights.

Weight / Diameter Table
The following table gives an approximate guide to the relative diameter size in millimeters, and weight of modern round brilliant cut diamonds of ideal proportions.