About Colored Diamonds
Kaleidoscope of Color
Of all the gems found on earth, nothing surpasses the palette of natural
or enhanced co
lor
diamonds for beauty, distinctiveness and desirability. Known as fancy-color
diamonds, they occur in virtually every color and shade of color. Ruby red,
baby pink, grass green and sapphire blue diamonds rank among the rarest
and most precious of all gems.
Fancy-color
diamonds possess a distinctive look not found in any other colored gem.
Whatever the actual “body” color seen in a fancy-color diamond,
it is augmented by the presence of numerous pinpoint flashes of other colors,
which are the result of diamond’s high dispersion – diamond’s
ability to break up each ray of reflected light into an array of spectral
colors. For example, a “yellow” diamond may be yellow, but you
may also 
see
pinpoint reflections of green, blue, orange and so on. The body color of
the diamond, combined with its high dispersion, creates a fiery scintillation
not found in any other gemstone. Even brown diamonds, once regarded as “too
common” to use in fine jewelry, are very much in vogue today. Their
warm neutral colors and fiery dispersion create a special allure, and since
they are so much more affordable than other fancy choices, jewelers worldwide
are now showcasing diamond jewelry containing brown diamonds in every shade
from the palest beige to the deepest, richest brown tones.
But keep in mind that there are also techniques for transforming
off-color diamonds into fancy colors, so before buying any fancy-color diamond
it is important to determine the origin of color, that is, whether the color
is natural or the result of treatment. There is nothing wrong with buying
a treated-color diamond as long as you know it is treated and it is priced
appropriately, usually at a price that is dramatically less than a comparable
natural-color diamond.
What Causes the Color?
Natural color in diamonds usually results from the presence of trace elements,
although in 
some
cases it can result from exposure to radiation naturally (as it was forming
in the earth) or from damage to the crystal lattice structure. Natural-color
yellow diamonds get their color from the presence of nitrogen, for example,
and blue diamonds, from boron or hydrogen. In diamonds where color is due
to particular trace elements, the presence or absence of those trace elements
can be ascertained through sophisticated testing procedures and can provide
an important key in determining whether color is natural or artificial.
The situation is different with green diamonds. The color seen in natural-color
green 
diamonds
does not result from the presence of trace elements; green diamonds owe
their color to exposure to radiation as they were forming in the earth,
eons ago. This creates an unusual dilemma for gem testing laboratories because
there are also treated-green diamonds that have been created by humankind
using modern radiation techniques. Since radiation is the cause of color
in both cases, it poses some identification challenges for laboratories.
In some cases a natural-color green diamond will contain certain unique
identifying characteristics that distinguish it from the treated stone,
and in some cases a treated-green diamond will exhibit characteristics that
identify it as treated. But many green diamonds lack conclusive evidence
for positive identification. In such cases, a laboratory report will indicate
that a positive determination cannot be made with gemological data currently
available. This leaves the door open to the possibility that a positive
determination might be made at some future time as new data come to light
from continued research and technological advances, but there are no guarantees.
In any event, if you are seeking a natural green diamond you must understand
that it may be more difficult to find one with laboratory documentation
confirming that the color is natural.
Fortunately,
gem-testing laboratories are usually able to positively confirm origin of
color in fancy-color diamonds, and cases where they cannot are the exception
rather than the rule. For this reason, and since origin of color has such
a significant impact on rarity and cost, it’s not recommend to purchase
a natural-color diamond without laboratory verification from a respected
lab such as the Gemological Institute of America.
THE 4C’S
To succeed in buying fancy-colored diamonds, you must take time to learn
as much as you can about them. It’s important to take time to understand
the 4C’s as they relate to fancy color diamonds – especially
the subtle nuances of color and their impact on value – and to develop
an eye for the important differences that affect not only the beauty and
desirability of a particular stone, but its cost.
While the 4C’s apply to fancy color diamonds as well as to colorless diamonds, the emphasis is clearly on “color.” In general, the rarer the color, the less impact clarity and cutting have on its value; the less rare the color, the more important clarity and cutting become. Many reports on fancy-color diamonds do not even include a clarity grade for information regarding cutting and proportioning except for the stone’s shape.
When seeking a fancy color diamond, color is so paramount that it is important to understand how color is graded. You must carefully evaluate purity of color, depth of color (tone and saturation) and color distribution throughout the stone.
To properly evaluate the color of a fancy color diamond, the stone must be viewed from the face up position – looking at it with the table up, as you would see it when mounted in a piece of jewelry. From this position, evaluate each of the following characteristics:
Purity of Color
This
refers to the hue and the purity of the hue. Let’s take “yellow”
as an example. The color of a fancy yellow diamond might be described as
“yellow,” “orangish-yellow,” “brownish-yellow,”
“brown-yellow,” and so on. Understanding the differences in
the wording is very important. The final word in the color description is
the hue; the word or words preceding it are the modifiers of the hue.
Having no modifier means the color is a pure hue and, depending upon the color, can be very rare. Some color combinations are rarer and costlier than others. For example, let’s consider two diamonds where one is “orangy-yellow” and the other is “brownish-yellow.” In both cases, the hue is “yellow” but since orange is rarer than brown, the orangy-yellow stone would be more valuable than the brownish-yellow stone.
Now let’s look again at the description of the “brownish-yellow” stone. Here the primary color is yellow, with a lesser degree of brown modifying the color. However, if the words were reversed, it would tell us the diamond is “brown” with some lesser amount of yellow modifying the color. Again, since brown is a much less rare color, a yellowish-brown diamond would have less value than a brownish-yellow.
When considering a fancy color diamond, it is important to take time to understand the terminology used to describe the particular hue that interests you, what shades are available and how they compare in terms of rarity and value.
Depth of Color
This refers to the saturation of color combined with
the tone – that is, how “light” or “dark”
the color is. Most fancy-color diamonds occur in pastel shades. Deep colors
such as ruby-red or sapphire-blue are extremely rare and are among the costliest
of all gems. The dept of color is usually indicated from “faint”
to “vivid,” with the “vivid” classification indicating
the richest possible tone in any given color. Be wary of stones with a “faint”
grade, these stones often have such a weak tone that they do not appear
to be a “fancy” color at all, but merely a very tinted, off
color stone. These should sell for much less than a “light”
tone or deeper tones. Most diamond reports for fancy-color diamonds rank
tone-using terminology similar to the following:
Faint.
Very Light.
Light (these first three categories are not truly “fancy colors”).
Fancy Light.
Fancy (yellow, orange, brown, blue or whatever the color).
Fancy Dark.
Fancy Deep.
Fancy Intense.
Fancy Vivid.
The
classification pertaining to the depth of color is extremely important.
One tonal difference can dramatically affect value. But you must also understand
that the terminology and gradations used to indicate the depth of color
– the tonal scale – is not the same for every color. If you
are seeking a yellow diamond, for example, and decide you want a color that
is darker in tone than “Fancy yellow,” the next classification
would be “Intense;” you would be wasting your time searching
for anything between “Fancy yellow” and “Fancy Intense”
because in yellow diamond there are no classifications between the two.
On the other hand, if you are looking at brownish yellow diamonds, there
is a “Deep” classification that is darker than “Fancy
brownish-yellow” but more affordable than “Intense.” In
blue diamonds, you will also find a “Deep” classification.
To accurately evaluate rarity and value, and to be sure you have found the depth of color that best suits your needs, you must be sure to find out what the specific tonal classifications are for the particular color you are considering.
Evenness of Color
The report will indicate whether the color is evenly dispersed under “Distribution.”
The distribution of the color should be “even” but this is not
always the case. Sometimes color occurs in zones, alternating with colorless
zones, and the report will indicate “uneven” color distribution.
Such stones may appear to have even color distribution when viewed from
the top and may be lovely and desirable, but they should cost less than
one that has “even” distribution.
Always view fancy-color diamonds in more than one type of lighting environment to determine color trueness.
One factor that is extremely important in the case of fancy-color diamonds is the trueness of the color in different lighting conditions. Where fancy-color diamonds are concerned, the color can change so dramatically depending upon the type of light in which it is viewed that it may no longer appear to be the color described on the report at all or may not be one you like.
TREATMENT
In
addition to a rainbow of colors that occur naturally, diamonds can be transformed
by treatments into beautiful, desirable colors using several techniques.
Radiation has been used for many years to change tinted, off-white diamonds
into various shades of yellow, blue and blue-green, and in most cases can
be easily distinguished from the natural by any competent gemologist. But
new techniques are creating new challenges, and determining whether color
is natural may require very sophisticated, high-tech procedures only available
at a major gem-testing laboratory.
HPHT Processes
Most retailers are now aware of the technique known as “high-pressure,
high-temperature annealing” that is being used to transform very off-white
and brownish diamonds into “colorless” and “near colorless”
stones. This technique is also used to transform these diamonds into a variety
of “fancy” colors, from yellowish-green and greenish-yellow
to exquisite shades of pink and blue. While the yellowish-green and greenish-yellow
diamonds often have a distinctive look that sets them apart from most diamonds
of comparable natural color, this is not the case with pink and blue, which
are very difficult to distinguish from the natural.
There is nothing wrong with buying a diamond that has obtained its color through treatment. Increasingly, fine jewelry designers are using color-treated diamonds to create distinctive jewelry at very attractive prices. But it is important to know whether the color is natural or the result of a treatment so you know you have paid an appropriate price.
CLARITY AND CUTTING
Many fancy-color diamond reports don’t include a clarity grade, especially
if the color is exceptional or very rare. When a clarity grade is provided,
the grading is based on the same criteria used for colorless diamonds. But
it’s important to understand that in fancy-color diamonds, flawlessness
is even rarer than in colorless diamonds.
Fancy-color diamonds are often in the SI (slightly included) range; I1-I3 (imperfect) grades are also common. In the fancy colors, however, SI and I grades don’t carry the stigma associated with these grades in colorless diamonds, especially if the stone has a rare or unusually deep color. This is not to say there are no “flawless” fancy-color diamonds or diamonds in the rarer clarity grades. But if the color is rare, and the diamond also has a high clarity grade, the cost will be disproportionately much higher.
As with colorless diamonds, enhancement techniques are being used to improve the appearance of fancy-color diamonds by filling fractures and lasering black inclusions so they are no longer visible.
Cutting and Proportioning
Most reports on fancy-color diamonds lack information pertaining to cutting
and proportioning. As with clarity, the deeper and/or rarer the color, the
less important the cutting. However, we should mention certain shapes are
more common among fancy-color diamonds because, in addition to proportioning,
the shape itself and the cutting style (that is, step-cut vs. brilliant
cut) can affect the intensity or evenness of the color.
When buying a fancy-color diamond, you must allow some flexibility where shape is concerned. Certain shapes are rare and difficult, if not impossible, to find in fancy colors, while others are much more readily available, in almost any color. The emerald cut is especially difficult to find, and even round stones may be difficult to find in a particular color. The radiant cut, however, is found frequently.
Today’s modern radiant and princess cuts have become especially popular
for fancy-color 
diamonds
because the shape, proportioning and facet arrangement intensify the color.
On the other hand, it’s extremely rare to find a fancy-color diamond
in an emerald cut because the color won’t look as intense.
Some Shapes Are Less Desirable
In addition to shapes that are especially desirable, some are not as desirable
in a fancy-color diamond because they may cause the color to appear uneven.
This often happens when a fancy-color diamond is cut into a pear or marquise
shape. These shapes usually exhibit a bow-tie effect across the stone’s
center – an effect created by light leakage – which usually
causes the color to appear lighter across the area of the bow-tie. Sometimes
the difference is slight; sometimes it’s pronounced. Such stones should
sell for less; the more visible the color difference, the lower the cost.
