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Diamonds need a Pedigree in the form of a certifcate.

3/31/2012

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Although nature created  the colored diamond, in today’s marketplace that diamond is just a beautiful
stone without ancestry. It must earn its pedigree in the form of a certificate.
While there are many labs examining and grading fancy color diamonds, for the
U.S. market, a Gemological Institute of America (GIA) cert is the most widely
used.And in order for that certificate
to carry weight in the industry, it has to be backed up by the evaluation of a
trained colored diamond grader. 
  The process of becoming a
diamond grader begins with a series of seven tests that eliminate candidates
with limited color acuity, as well as those who don’t have the ability to
“reason” their way to the essence of a diamond’s color. That ability, according
to John King, chief quality officer of the GIA Laboratory, is crucial to colored
diamond grading.
 Approximately one-third of
those who go through the GIA vision screening, which can be completed in about
three hours, qualify on their first attempt. Some who don’t make it through on
the first try return to go through the testing again, and, John King says, “We
have seen improvement in some who have taken the tests more than
once.”

 
COLOR VISION
BASICS

In the general population, 8 percent of men and just
.5 percent of women have red-green color blindness, the most common form of
color vision deficiency. Outside that group, a person’s color vision can range
from superior vision — able to discern the most subtle color variations — to
vision that, while not considered color blind, is also not particularly sharp. 
 
The innate color vision of
candidates interested in becoming graders is evaluated first at GIA because it
is an essential, nonnegotiable qualification for the job. Graders may rotate
among various tasks in GIA’s lab, but they need excellent color acuity to
perform any job on any diamond, whether colored or “colorless.” The differences
between a Y and Z diamond or between fancy light and very light colored diamonds
are extremely subtle and a superior natural color acuity is necessary to first
“see” those subtleties and then to identify and evaluate them. 

THE FIRST OF THE
TESTS

The color vision test, familiarly known as the “dot”
test, is the universal testing tool for identifying color deficiencies in
individuals. It is a standard detection test used to screen applicants for work
in a wide variety of assembly, design and laboratory industries. In the test,
the subject is shown a sequence of test plates flashed on a screen, each of
which contains a combination of various colored dots. Within the background
dots, dots in contrasting colors form a number, which the applicant is asked to
identify in five seconds. With each successive test plate, the contrast between
the background and the number grows ever more subtle and more difficult to
discern. For those with color vision deficiencies, the numbers quickly become
invisible. In fact, many people first discover they have a color deficiency when
they face the colored dot patterns of the test and fail to see the numbers. 
 
The remaining six tests in
screening diamond grading applicants at GIA are conducted with the Gretag
Macbeth Judge II light box, which is equipped with extremely bright, extremely
white light. Coincidentally, the Judge II
light box is commonly used to grade diamonds.

 
SEEING THE COLOR
SPECTRUM

The Farnsworth
Munsell 100 Hue Test asks the candidate to organize 93 colors into four
groupings, reflecting the progressive, subtle gradation of colors from one end
of the spectrum to the other. The individual being tested physically moves
different colored pegs within two stationary colored panels in order from the
high — i.e., vivid — to low — i.e., pale — range of a particular color. The test
is carried out beneath simulated daylight provided by the light box, at a
distance of approximately12 inches to 15 inches. The test taker has 15 minutes
to sort out the four groups of colors. 

For the “color attribute”
aptitude tests using Munsell color chips, the applicant is first given a brief
explanation of three different color attributes — hue, tone and saturation. Hue
is the aspect that describes colors by specific name, either by the primary
color, such as red, green, or blue, or by some intermediary color between the
primary colors, such as reddish orange or bluish green. Tone describes the
lightness to darkness of a color; saturation measures the strength or purity of
a color. 

In a sequence of two tests
using 25 pairs of Munsell color chips arranged on small cards, the applicant
must consider the appearance relationship among these three color attributes. In
the first test, the chips have been chosen so that two of the three attributes
are the same; the applicant must discern the attribute that is different. For
example, the hue and tone may differ but the intensity of the color is the same.
In the second test, two of the attributes are different and the test taker must
find the matching third attribute. For example, both chips have the same tone,
but the hue and intensity differ. Each test must be completed within 15 minutes. 
 
Color matching is the
subject of the Macbeth Match Point test, in which the candidate moves two scales
of a color gradation slide back and forth in relation to each other to find the
point at which they match as closely as possible. An exact match is not possible
in this test. In Match Point, the so-called “metameric” effect of different
light sources is being judged — the phenomenon in which two objects match in
color under some lighting conditions but not others. Five minutes is allowed for
this test. 


THE FINAL
TESTS

Finally, in the concluding two
tests, the specific tasks and skills of a diamond color grader are evaluated.
The first is the most controversial aspect of diamond color grading as carried
out by the GIA — stone-to-chip comparison— in which diamonds are compared to Munsell
color chips. 
 
The controversy stems from
the fundamental differences in the two objects. The chip is flat, even in color
and opaque, while the stone is three-dimensional, absorbs and reflects light and
is transparent. Because of these differences, this test requires a huge leap
into a realm where apples are indeed being compared to oranges. The applicant
must find the color chip that is closest in hue, tone and saturation to the
diamond being examined.According to GIA, “this test determines if the
applicant can look beyond the complex visual details of the diamond and find a
single overall appearance that is close to the overall appearance of the chip
color.” The applicant must compare six pair-ups within 35 minutes. 

Munsell chips are used only
when the lab does not have a comparison stone to use. It is not possible for GIA
to have a real diamond as a comparison stone in every single shade of diamond
submitted to them for certification.Diamonds occur
in thousands of tones; even if such stones could be found for every match, no
lab could afford to buy all of them.
G
RADING AGAINST
MASTER STONES

In the final GIA test, an individual is asked
to grade five yellow diamonds against a range of GIA yellow master stones.
Yellow diamonds are used because they constitute the broadest family of hues
within one color category and also because they make up about 60 percent of the
colored diamonds submitted to the lab for grading. 

Although the applicant is
now grading apples against apples — a specific stone against a master stone —
the stones vary in cut, once again adding to the complexity of the test and
mirroring the actual real-life practice of grading diamonds. Assessing the
saturation of color between a pear shape and a round, for example, requires the
ability to consider all the angles of the two diamonds in order to discern depth
of color. Although diamonds are graded face up, the grader still has the
opportunity to rock the diamond back and forth to observe the color. The
applicant has 20 minutes to grade five yellow diamonds and place them within
categories ranging from fancy light to vivid. 
In all six of these color
comparison screenings for a position as a GIA diamond grader, King
says,“We
are teaching a way of observing that will allow the grader to gaze at the color
rather than the details.” He compares the process to seeing a Seurat painting.
If you look at it up close, you see the separate elements that go into the
painting. When you step back, you get the overall impression — the individual
“dots” of color merge to achieve the image the artist had in mind. So it is with
colored diamonds. “After the testing, we mentor them for weeks. In training, you
begin to understand their reasoning skills; how you think is part of the way you
see.” King says the successful grader must be able to put together all the
observations of the diamond to come to a conclusion. “They must reason their way
to a decision,” he adds.


Article from the Rapaport Magazine - March 2012

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The Cutter and the Diamond

3/31/2012

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In the world of fancy color diamonds, the cutter is a
partner with nature. The number of tones found within a colored diamond may be
infinite and coaxing the optimal color from the rough is a process both
scientific and artistic. It requires visionary cutters who, like Michelangelo,
find the David within the marble. They envision the gem they want; it’s simply a
matter of taking away the extraneous material. But, just as with David, only a
genius can take away exactly the right amount, in exactly the right places, to
produce the diamond masterpieces seen on these pages.
These two extraordinary
examples from within the red spectrum show how truly varied and exquisite
colored diamonds can be. At the same time, such stones pose the ultimate
challenge to the Gemological Institute of America (GIA), whose graders must
consider the multitude of varied tones within the stones before issuing color
and clarity grades.
THE EMBER
DIAMOND

For diamantaire Bruno
Scarselli, of New York City’s NBS Diamonds, the magnificent SI1, 1.26-carat
stone he named the Ember Diamond evokes the rich and varied tones of autumn
leaves in Maine. This octagonal stone was certified as fancy reddish orange by
the GIA, which examined it in minute detail. The Ember Diamond is believed to
have come from a rough found in the Democratic Republic of the Congo (DRC) in
Africa, formerly known as the Belgian Congo and more recently as
Zaire.
 
The Ember Diamond
The November 17, 2010, GIA monograph on the stone,
whose GIA cert is dated May 10, 2010, describes the careful thought that went
into extracting the best color from the rough. “In general, colored diamonds
benefit from a style of cutting that reduces the tight patterning of bright and
dark areas we associate with colorless to near-colorless diamonds,” the GIA
wrote.“That patterning we cherish in colorless stones often masks the color in a
colored diamond. But to eliminate bright areas in dark rough would create an
overall dark stone, one that would likely appear brown, or gray in the case of
cool-hued rough.

In order to preserve the
rich dominant color within the rough, the cutter of the Ember Diamond employed a
variety of techniques. According to GIA, “With the chosen proportions and
interfacet angles, the octagonal shape — similar in symmetry to the round shape
— efficiently collects color in the center of the stone, resulting in a deeply
saturated face-up appeal. Broad, flat facets on the bottom of the stone allow
the color to return to the eye as relatively large planes, thus becoming the
focus for the observer.”

 The cutter’s skills produced
an optimal and distinctive visual experience. Only those who understand the
challenges involved in cutting such a stone can truly appreciate the
achievement.

 
THE SHELLEY
RED

In modern gemology,
designating a diamond as fancy red with no modifiers is a rare event. One such
rarity is the .69-carat VS2 fancy red stone dubbed the Shelley Red by colored
diamond expert Stephen Hofer and owned by Shelley Diamonds. The stone is a
pear-shaped modified brilliant cut that, Hofer notes, “helps to strengthen and
concentrate the apparent red color” seen in the stone face up. Further, he
indicates, this face-up color strength or saturation is found at precisely the
point within the GIA’s three-dimensional box where the pure color red is
situated. This is an extremely rare natural occurrence. This purity of red is
quite unusual for a natural diamond…. When viewed in the face-up direction under
average daylight, i.e., 6500K or D65 illumination, the red color is evident to
the eye, providing visual confirmation of the color measurement.” 
 
The Shelley Red
Hofer goes on to say that the Shelley Red, which
received its GIA cert on February 14, 2011, “has a distinct red hue when
compared against the most saturated red color chip in the Munsell color notation
system, the Munsell 5R 4/14 color chip.”
 
While the Shelley Red does
display hints of pink, Hofer sees it as having “extraordinary body color with a
lightness that measures near the borderline between the medium and medium-dark
range. The inherent saturation measures just above the borderline between the
weak-moderate and the moderate categories.”

 Hofer dissects the interior
of the diamond, noting that“This stone exhibits obvious pink/red graining inside
the crystal…. This complex mosaic of bright and deep, pink and red reflected
colors gives this diamond its unique beauty and singular appearance as a
gemstone.” 

Cutting played a prominent
role in achieving the fancy red grade for this diamond.In his December 14, 2011, monograph on the stone, Hofer
writes, “This well-made modified brilliant cut with four pavilion main facets
also distributes the color fairly evenly, giving this gem a high degree of color
symmetry.” He concludes that red diamonds “continue to be regarded as the
‘rarest of all’diamond colors and that they are seldom to be seen in the diamond
trade, possessing extreme natural rarity and each one is considered a true
collector’s item.”


Article from the Rapaport Magazine - March 2012.

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First Post!

3/31/2012

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Start blogging by creating a new post. You can edit or delete me by clicking under the comments. You can also customize your sidebar by dragging in elements from the top bar.
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    Mary has a love for diamonds and is a GIA Graduate

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