Diamond Color Grading
by Ms Nandita Ray
Diamond has Nitrogen atoms as the main impurity. The common concentration of this impurity is 0.1 %. If the nitrogen atoms are set in pairs then they have no affect on the diamond and make the diamond colorless. Such diamonds fall in the Type 1aA. If the nitrogen atoms are present in clusters they impart a brownish or yellowish hue to the diamond. These are clubbed in 1 aB.
Let us not be too particular, it is
better to have old second hand
diamonds than none at all', observed
Mark Twain. Diamonds are worth more
than their weight in gold. Diamonds
are truly prized, even though they
are crystalline carbons in their
natural form. Diamonds are formed in
the deep recesses of the earth by
tremendous pressure and temperature.
Diamonds come in many colors.
Colorless diamonds are rare. There
are diamonds of various colors. The
most common color is yellow. This is
because the chemical impurities and
structural defects affect the color
of the diamond. Chemically pure and
structurally perfect diamonds allow
light to pass through it and break
up into the seven colors of the
rainbow. Transparent and colorless
diamonds are very expensive.
Diamonds with their own natural
color are unique and are called
'fancy diamonds'. Such diamonds are
rare and very expensive.
A diamond's color can either enhance
its value or decrease it. Most white
diamonds with more yellow hue loses
its price while a diamond with an
intense pink, green, purple, blue or
yellow becomes more valuable since
they are rare. Out of all the
colored diamonds, red diamonds are
very rare. Diamonds may also have
grey, orange brown or black color.
However, most diamonds will always
have a very slight hint of yellow.
How color grading is done?
Diamonds are scientifically divided
into two classes and several sub
class. This is based on the
blemishes present in them, the
nature of the blemishes and also how
these blemishes absorb and reflect
color. Diamond has Nitrogen atoms as
the main impurity. The common
concentration of this impurity is
0.1 %. If the nitrogen atoms are set
in pairs then they have no affect on
the diamond and make the diamond
colorless. Such diamonds fall in the
Type 1aA. If the nitrogen atoms are
present in clusters they impart a
brownish or yellowish hue to the
diamond. These are clubbed in 1 aB.
Ninety eight percent of the diamonds
mined are 1a and rest is a mixture
of 1aA and 1aB. The diamonds that
fall in this category are mined in
the Cape Province of South Africa.
The rare Canary diamonds, which are
a vogue with the Rappers, belong to
the rare breed of diamonds which are
type 1B. The Nitrogen atoms in such
diamonds are spread through out the
crystal and not present in groups.
This gives the diamond a deep yellow
or brown tint. Only 0.01 % of such
diamonds are found. Synthetic
diamonds which contain Nitrogen fall
into the 1b group.
Type 1 diamonds have the capacity to
absorb in the infrared and
ultraviolet regions. They also have
fluorescence characteristic. Type 2
diamonds have fewer Nitrogen atoms
and can be colored pink, red or
brown. These diamonds are rare. They
are mostly mined in the Australian
mines. Presence of Hydrogen gives
the diamond a blue hue.
Color grading of diamonds is based
on the color intensity scale as
established by the
GIA i.e. the
Gemological Institute of America.
There are other diamond grading
agencies that have their own grading
scale, the European Gemological
Laboratory or the American
Gemological society. But the
accepted standard of grading is
based on the GIA. It uses D to Z
scale for grading the color of non
fancy white diamonds. D is
absolutely colorless while Z is
D E F - colorless
G H I J - near colorless
K L M - faint yellow or brown
N O P Q R - very light yellow or
S T U W X Y Z - definitely light
yellow or brown color.
Diamonds that are at the top of the
scale are also called 'high color'
diamonds. Those that are placed at
the bottom of the scale are called
'low color' diamonds. Diamonds that
have a deeper color than Z are
considered 'fancy diamonds'. Such
diamonds are graded based on the
characteristics of color present.
This system of grading is similar to
the grading of colored stones like
Ruby, Emerald or Sapphire. Deeper
the color the rarer it is. Colors
such as deep purplish pink are very
rare and thus most expensive.
How to test diamond color ?
There are two ways to test the color
of a diamond. A stone can be
compared and its color determined by
using reference set or master set of
stones. The best way to use this set
is under natural light. The master
set has stones graded according to
the colors they exhibit. This set is
made up of cubic zirconium. This way
of determining the color is not
always perfect. The best and
decisive method to grade color is by
using a color meter. This is an
electronic instrument that is used
to measure the optical
characteristics of the stone and
reveal the color. The Gram color
meter which is calibrated according
to GIA and AGS standards easily
grades color and reduces the risk of
The diamond should be tested when it
is loose. Setting affects the color
as does the metal that has been
used. The GIA's scale is the
accepted standard of grading the
color of diamonds. The European
Gemological Laboratory has its own
method. The table below indicates
the system they use.
D E F G||Finest white||colorless|
|I||commercial white||very faint yellow|
J K L ||Top silver
or brown color|
O P Q||Light Cape to
light yellow or brown|
|R||Cape to Dark Cape||definitely
yellow or brown|
U V W X Y Z||Dark
As clear the terminology varies but
grading is similar. There is no
standard scale for measuring colored
diamonds. They are graded in two
ways, the basic hue or tint of color
and secondly the intensity of the
color present. The basic hue will be
pink, yellow, green, brown or
purple. These two qualities
determine the value of these so
called 'fancy diamonds'. The deeper
the color the more expensive the
diamond even though they might be of
the same size, shape and clarity.
The GIA has 9 categories to grade
2 very light
4 fancy light
6 fancy dark
7 fancy intense
8 fancy deep
9 fancy vivid.
The GIA has some guide lines that
need to be adhered to strictly while
grading the color of a diamond.
1. The color of a diamond can only be
compared to the color of the
'control or master set' of stones.
2. Graded diamonds must be loose
3. The diamonds must be viewed with
4. Diamonds must be placed table down
5. A letter system from D to Z is
used to identify the color
6. D grade is given to only rare and
absolutely colorless diamonds.
The GIA diamond reports indicate
whether a diamond changes its color
radiation. Diamonds with this
quality can appear to change color
under fluorescent lights.
Diamond's that produce a blue color
appear colorless under UV lights.
sometimes used to enhance the color
of a diamond. Many other testing
also including these specifications.