CONTENT: PART I: has introduced you to the following topics: * Who should read this page and why? * Short overview of the "4 C's"- the 4 main Characteristics of the diamond gem; * diamond Shapes & Styles ; * How are diamonds Priced.

Here, in PART II, you are offered an in-depth study of the "4C's" (diagrams included...)



Welcome to Van-Daaz's "In-depth" information center.

The 4C's 'On...:

Cut, Clarity, Color & Carat

The 4-C's namely, Cut, Clarity, Color and Carat Weight help to categorize and grade the diamond using universal terminology which determines also the price and value of the diamond. At the same time familiarity with the 4 C's helps individuals to better understand the diamond's natural characteristics and thus to decide knowledgeably which combination is the most suitable and most desirable for them .

Proportions and cut determine the brilliance (reflection of light from inside the diamond) scintillation (reflection of light from the surfaces of its facets) and dispersion (colour refraction-the twinkling of colours especially as the diamond is moved about) of a diamond. In the diamond trade, "Cut" (or, "Finish") consists, conventionally, of two separate grading parameters: 'Polish' (usually mentioned first), or, the actual finishing of the different facets' very surface, their very external layer, and, 'Symmetry'. In order to maximize this brilliance, the diamond cutter must place each of the diamond's facets, which act as light-dispersing mirrors, in exact geometric relation to one another. The symmetry of the placement of the facets, the integrity of each facet's borders, its alignment with all other bordering facets, whether or not the table plain is parallel to the girdle plain, whether or not and the extent to which the table or culet are off-center, the levelness (as opposed to waviness) of the girdle and perfect closure of all corners of each facet are contributors to the diamond's over all 'Symmetry' grade. When no such imperfection can be discerned under X10 maginificatyion the symmetry is "Excellent"; If the imperfection is Extremely Hard to discern under X10 times magnification-- the symmetry is graded as "Very Good". If such mishaps are Very Difficult to discern under the same conditions-- the symmetry is graded as Good. We do not promote or sell lower grades ("Fair" and "Poor"). Most diamonds score a Good/Good 'Cut' grading-- Good Polish & Good Symmetry, that is. This type of finish guarantees, due to its demanding criteria ("Very Difficult to descern under X10 time magnificatio...") very satisfactory cut grading, nice overall appearance dispersion & scintillation. On a classic Round Brilliant cut diamond, fifty eight (!) facets must be precisely aligned. Despite the somewhat loose use of the terms "Cut" & "Proportions"--strictly speaking, "Cut" pertains to the"Symmetry" & "Polish" grading (the use of the word "cut", sometimes , in reference to the diamond's shape, as in, e.g., "Radiant Cut" has nothing to do with the "Cut grading"). Proportions are referred to, simply, as "proportions" (rather than "Cut"). Few diamonds are cut to exacting standards since diamond cutters try to maximize their returns on the raw material by leaving the stone as large as possible with minimum waste. As a result, the proportions, symmetry and perfection of the cut and shape may be delegated to play a secondary role. The result is usually a compromise between profit (e.g., size) and beauty (perfection of cut, proportions and shape).

Marcel Tolkowsky is credited with calculating in 1919 the ideal proportions and facet angles that create maximum 'balanced' brilliance, scintillation and fire. Unfortunately the "ideal cut" results in smaller weight yield from the rough diamond crystal and is rarely practiced. Most cutters today slightly compromise Tolkowsky's "ideal cut" in what has come to be known as the "American Brilliant Cut" or "Modern American (brilliant) Cut" (see below). The slightly modified cut still creates impressive results. At the end of 1998, however, a lengthy 6 year meticulous research in the GIA labs yielded some shocking new results (see below).

When the diamond is well proportioned the path of a beam of light is returned directly back to the eye instead of escaping through the bottom or sides of the cut diamond, as a result the diamond will be more lively and brilliant.

A most important criteria of the Cut is the ratio of the depth to its diameter ( i.e. Depth/Diameter whereby the diameter is that of the girdle's--see diagram; In fancy shapes it is the girdle's shortest measurement). In order for the diamond to be considered within the "Ideal" tolerance bracket its depth ratio should be between, approx. 58/100 and 62.9/100 or, "58%" and "62.9%" respectively (see illustration). The measurements are taken in millimeters through the use of a Leveridge Gauge or Micrometer."Table" diameter percentage ( see illustrations for definitions of the names of the different diamond facets ), "Crown" angles and "Girdle" thickness & symmetry are also important. Each of these proportion criteria has its tolerance range. The GIA's 1998 research release points out how detrimental those could also be. These tolerance ranges, loosely speaking, are those manifested in the "American Brilliant Cut". Thus, acceptable table proportion tolerance range for the practical equivalent of the ideal cut ("The Modern American Cut") is larger than the allowed deviation range for its depth: tables are allowed the proportion range of approx. 52% to 59%. The European market, on the other hand, is less preoccupied with Tolkowsky's notion of the 'ideal cut' creating, allegedly, a 'prefect balnce' of brilliance, scintillation and fire as expressed in his, so called, "ideal" cut or, in its "American Brilliant Cut" extension. Europe is distinctively inclined, rather, towards diamonds with Tables between 59% to 66%, as diamonds of these Table proportions look larger to the eye and their brilliance is improved substantially (albeit, admittedly, at some expense of the diamond's scintillation and colour dispersion). Reputable European grading labs such as the HRD or IGI of Antwerp, grade such Table proportions as falling within the "Very Good" category. Similarly, depths ranging from 55% to 63.9% are also considered by the same market and grading labs to be of "Very Good" proportions. Some cutters and dealers promote a 'safe' compromise of a catchy sound--the "60/60" combination (depth of 60% and a table of 60% as well)--taken somewhat flexibly--+/-2, that is...

In fancy cut diamonds (Princess Cut, Emerald, Marquise, Oval, Pear etc.) proportions are measured in relation to the diamond's width--the girdle's cross section narrowest measurement- and tend to be considerably larger (in the high 60's and 70's for squarish shapes). Remember, however, that if they were close to the ideal cut standards--those proportions would be too low in the longer directions of the diamond (unless the culet was sufficiently stretched as well). It is a simple manifestation of the impossibility of "squaring the circle"--what works out for the circular shape simply cannot be fully applied to a square, rectangle or a heart shape...

In girdles, even though girdle thickness of very-thick does not affect a diamond's brilliance it does, however, render the diamond's appearance somewhat smaller as the bulk of its weight is concentrated in the girdle area. The girdle's affect on a diamond's brilliance is negligible. Faceted girdles, however, slightly improve a diamond's brilliance (provided that they have a sufficient number of facets--see below--) as the facets reflect the light back, not allowing, by and large, much of it to escape. Extremely thin girdles, on the other hand, should be avoided due to their fragility in the setting process and after (if exposed).

After 6 years of extensive and intensive research a scientific team of the GIA laboratories published the shocking results of their research into diamond proportions and their effect on diamonds brilliance (the reflection from within the diamond of light falling on and onto its crown). The results were published in the GIA's official publication Gems & Gemology" (Fall 1998 issue). Shorter reviews and discussions appeared in the diamond trade's JCK magazine (January 1999, February 1999) and in the National Jeweler (February 1st.1999). The research paper was co-authored by GIA senior researchers T. Scott Hemphill, Dr. Ilene M. Reinitz, Dr. Mary L. Johnson and Dr. James E. Shigley. While Marcel Tolkowsky based his calculations on a 2-D (two dimensional) model, the GIA team, abled by powerful computers to conduct large number of calculations in short periods of time, has created a 3-D (three dimensional) simulated diamond model capable of tracing light beams path inside the diamond (based on known diamond optical properties--its refractive qualities); The team proceeded to define and measure what they called "WLR" or, Weighted Light Return, a mathematical equivalent, by and large, of a diamond's brilliance. The computer model revealed shocking truths... Thus, after examining more than 20,000 combinations of Table & Depth proportions, Crown and Pavilion angles, as well as actual 67,621 GIA reports on file, the research has established, in its conductors view that--

  • First--there is not a single 'Ideal Cut' (=ideal proportion-combination) surpassing all other combinations of proportions in its brilliance (measured as WLR)--but rather several, completely different combinations which are of high and often equal WLR/Brilliance level, surpassing the level of what we call today "Ideal Cut(s)"... Thus, on a scale of 0 (poorest or no-brilliance) to 1 (maximum brilliance or full 100% reflection from within of all light hitting the crown) Tolkowsky's ideal cut scored 0.281 (described in the paper as "moderate bright") , the average market cut--0.270 to 0.275. Other combinations (plural!) newly discovered in this project scored 0.285 and up to 0.300!.
  • The brightest diamond proportions were... 54% table, Pavilion of 42.4 degrees (Tolkowsky calls for 40.75), 27.3 degrees of Crown Angles (Tolkowsky called for 34.5; The GIA mentions in comments of shallow crown diamonds, as a negative consideration, "Crown angles less than 30 degrees"...). Another "Very Bright" combination was of 61% Table, 26.3 degrees Crown angles (!) and 42.5 degrees of Pavilion angles... The inter-relations amongst all considered proportions and angles have proven intricate and surprising. Vastly different and far-apart combinations have proven to be of equal brightness merits.
  • Crown angles have proven most detrimental to a diamond's brightness, peaking (when all other variables are constant) at... 23 degrees (!); Pavilion angles, similarly, peak at 40.7 degrees (as in Tolkowsky's cut).
  • Table proportions' affect on brilliance are very 'erratic', in strong dependency on Crown and Pavilion angles. Although, as a rule of thumb, smaller tables tend to fair better, still, an, e.g., 65% table will provide more brightness provided, however, that the diamond's Crown angles are 23 degrees (to 40.7 of the pavilion's). The brilliance of tables of above 62% is high provided that the Crown angles of such diamonds are less than 29.3 degrees...
  • Faceted girdles (most common in North America), assist brightness (number of facets should be between 32 and 144-- common-place in North America-- and without difference in brightness (brilliance) levels within this range).
  • "Crownless" diamonds--diamonds from the girdle-down only, that is--would be...well, the brightest ..! (their aesthetic value will have, however, to be debated...).
  • Culet size , even when very large (e.g., 12% (!)) has negligible affect on the diamond's brilliance.

Similar results have been reached by researchers at Moscow University-- a country known for its excellence in diamond cutting and great mathematicians. You may see those results at the page dedicated to those results--http://www.gemology.ru/cut/ at their site. The page includes also animated illustrations and different diamond proportions modeling and light-ray tracing software!

Arguments, preliminary conclusions and issues:

Admittedly the research did NOT cover scintillation and dispersion. The researchers answer to this accusation is that neither did Tolkowsky take those into consideration in a fully quantified manner (despite the myth...), if only for the most prosaic of reasons--there is not yet a quantifiable, adequate definition of those (the research will try to do exactly that in the coming years). So Tolkowsky too could not measure those and consider them for his final "Ideal Cut" proportions...

Furthermore--The research was based on an idealized, mathematical/geometrical 3-D model, what they refer to as a "virtual diamond", no consideration given to deviation from a perfect symmetry, flawless clarity and complete colorlessness--unlike most commercial diamonds. The researchers answer: Tolkowsky and other inventors of variety of so called "Ideal Cuts" have not taken those into consideration either. Those, incidentally, are also scheduled for future study.

How should these results affect your choices?