More than 100 million diamonds are sold in the United States each year, yet most consumers know very
little about the product they are purchasing, and how that product is valued. The 4 Cs represent the four
variables that are used to calculate the quality and value of a diamond. Both rough and cut diamonds are
separated and graded based on these four characteristics.
As a consumer, your first step in shopping for a diamond should be to learn and understand the "4 Cs"
diamond grading system. The more you know about how quality relates to value with diamonds the less
likely it is that you will get ripped off. It is important to learn how to read and understand the details of a GIA
(Gemological Institute of America), AGL, or AGS (American Gem Society) "Diamond Certificate" or Sarin
"Diamond Grading Report" or GIA 'Diamond Dossier®.' You will also want to familiarize yourself with the
Federal Trade Commission (FTC) guidelines on jeweler conduct and consumer awareness. This will help
you immensely when you are comparison shopping for diamonds.
When jewelers judge the quality of a diamond cut, or "make", they often rate "Cut" as the most important
of the "4 Cs." The way a diamond is cut is primarily dependent upon the original shape of the rough stone,
location of the inclusions and flaws to be eliminated, the preservation of the weight, and the popularity of
certain shapes. Don't confuse a diamond's "cut" with it's "shape". Shape refers only to the outward
appearance of the diamond and not how it is faceted.
The Importance of Cut Quality
A diamonds cutting proportions, directly effects the refraction of light. In other words how well a diamond is
cut, has everything to do with how much light is refracted from a stone and the degree of sparkle,
scintillation and brilliance a diamond shows.
When a diamond has a high quality cut (ideal cut), incident light will enter the stone through the table and
crown, traveling toward the pavilion where it reflects from one side to the other before bouncing back out
of the diamond's table toward the observer's eye (see Fig. 1 below). This phenomenon is referred to as
"light return" which affects a diamond's brightness, brilliance, and dispersion. Any light-leakage caused by
poor symmetry and/or cut proportions (off-make) will adversely affect the quality of light return.
The "Shallow Cut" and "Deep Cut" examples in Fig. 2 show how light that enters through the table of a
Modern Round Brilliant diamond reaches the pavilion facets and then leaks out from the sides or bottom
eye means less "Brilliance". In the "Ideal Cut" example, most of the light entering through the table is
reflected back towards the observer from the pavilion facets.
GIA's new cut-grading system is based on averages that are rounded-up to predict 'light performance,'
while AGS uses a more exacting combination of proportional facet ratios along with ray-tracing metrics
to calculate light return. The "Ideal" designation is an AGS term that is not found on an GIA report. The
GIA will give a symmetry demerit for what it calls "non-standard brillianteering" which some
manufacturers use to 'improve' on the standardized Tolkowsky-type cuts.
The proportion and symmetry of the cuts as well as the quality of the polish are factors in determining
the overall quality of the cut. A poorly cut diamond with facets cut just a few degrees from the optimal
ratio will result in a stone that lacks gemmy quality because the "brilliance" and "fire" of a diamond
largely depends on the angle of the facets in relation to each other. An Ideal Cut or Premium Cut
"Round Brilliant" diamond has the following basic proportions according to the AGS:
* Table Size: 53% to 60% of the diameter
* Depth: 58% to 63% of diameter
* Crown Angle: 34 to 35 degrees
* Girdle Thickness: medium to slightly thick
* Facets: 58 (57 if the culet is excluded)
* Polish & Symmetry: very good to excellent
Symmetry and Polish
diamond is faceted. Where cutting proportions affects how much light is being returned to the eye, symmetry
affects the break up of that light (the spheres of light or sparkle and scintillation you see when you turn the
diamond). An example of poor symmetry would be poorly shaped facets, facets that do not meet up at perfect The
symmetry of a diamond is related to the overall geometry of the diamond. In other words, how well the points,
Uneven girdle and misshaped tables. Cutting problems which effect symmetry can occur during the faceting
process, when one incorrect facet angle can throw off the symmetry of the entire stone. The chart below shows
several common problems to look for.
Perfectly formed Hearts and Arrows patterns with eight hearts AND eight arrows (above, left) are only
found in diamonds that meet the American Gem Society Laboratories' "0" Ideal Cut specifications.
The IdealScope was invented by Kazumi Okuda in the 1970's, and its later incarnation, the
"FireScope," was invented by Ken Shigetomi and Kazumi Okuda in 1984. The first official H & A
manufacturer, Takanori Tamura
Carat weight is one of the 4 C's, representing the four variables that are used to calculate the quality
and value of a diamond. Both rough and cut diamonds are separated and graded based on these
four characteristics. As a consumer, your first step in shopping for a diamond should be to learn and
understand the "4 C's" diamond grading system.
A diamond or gemstone's "Carat" designation is a measurement of both the size and weight of the
stone. One "Carat" is a unit of mass that is equal to 0.2 grams (200 milligrams or 3.086 grains) or
0.007 ounce. A carat can also be divided into "points" with one carat being equal to 100 points, and
with each point being 2 milligrams in weight. Therefor, a 1/2 carat diamond would be 50 points, a 3/4
carat diamond is 75 points, and a 2 carat diamond is 200 points.
When a single piece of jewelry has multiple stones, the total mass of all diamonds or gemstones is
referred to as "Total Carat Weight" or "T.C.W."
The word "Carat" is derived from the Greek word keration, or "seed of the carob". In ancient times,
carob seeds were used to counterbalance scales, and as a benchmark weight due to their predictably
Hearts and Arrows Diamonds
A perfectly proportioned ideal cut that is cut to the exacting specifications of a Tolkowsky Cut, Eppler
Cut (European Standard), or a Scan D. N. Cut (Scandinavian Standard) will display a "Hearts and
Arrows" pattern when observed through a IdealScope (arrows only), or a H & A Viewer gemscope
All of the grades of diamond clarity shown in the table below, reflect the appearance of inclusions
within the stone when viewed from above at 10x magnification Higher magnifications and viewing from
other angles are also used during the grading process. In "colorless" diamonds, darker inclusions will
tend to create the most significant drop in clarity grade. In fancy-colored diamonds, light or pale
inclusions may show greater relief, making them more apparent, causing a greater drop in grade.
Diamond Clarity Designations
- FL - "Flawless" no inclusions at 10 x magnification
- IF - "Internally Flawless" no inclusions at 10 x mag. - small blemishes
- VVS-1 - "Very Very Small" inclusions hard to see at 10 x magnification
- VVS-2 - "Very Very Small" inclusions. VVS1 better than VVS2
- VS-1 - "Very Small" inclusions visible at 10 x mag. - not naked eye
- VS-2 - "Very Small" inclusions VS1 is better grade than VS2
- SI-1 - "Small" or "Slight" Inclusions or "Imperfections" may be "eye clean"
- SI-2 - "Small" or "Slight" Inclusions or "Imperfections" visible to naked eye
- SI-3 - Inclusions large and obvious, little or no brilliance
- I-1 to I-3 - Imperfect, with large Inclusions, fractures, and flaws
GIA Grading System
The chart in Fig. 4 explains the GIA grading system for inclusions and imperfections. Considerations in
grading the clarity of a diamond include the type of stone, point size and the location of inclusions.
Inclusions that are near to, or break the surface, may weaken the diamond structurally, therefore
reducing its value significantly. On the other hand, it may be possible to hide certain inclusions behind
the setting of the diamond (depending on where the inclusion is located), thus minimizing any negative
impact of the inclusion.
Most all natural diamonds contain small quantities of nitrogen atoms that displacing the carbon atoms
within the crystal's lattice structure. These nitrogen impurities are evenly dispersed throughout the stone,
absorbing some of the blue spectrum, thereby making the diamond appear yellow. The higher the
amount of nitrogen atoms, the yellower the stone will appear.
In determining the color rating of a diamond, the Gemological Institute of America uses a scale of "D" to
"Z" in which "D" is totally colorless and "Z" is yellow. The color chart in Fig. 1 explains the GIA grading
system for clear (not fancy-colored) stones.
Diamond Color Designations
* D, E, F - colorless (white)
* G, H, I, J - near colorless
* K, L, M - faint yellow or brown
* N, O, P, Q, R - very light yellow or brown
* S, T, U, V, W, X, Y, Z - light yellow or brown
The Four C's of Diamond Grading
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