Diamonds
Diamond Shapes
The most common shapes of diamonds
seen in
jewelry are pictured above. They include: Emerald, Heart, Pear, Round
Brilliant, Marquise, Radiant, Oval and Princess Cuts. Numerous variations exist on the above shapes, many of which may contain Trade
marks as to the use of their names. Other
common cuts not shown above include Baguettes (both straight and tapered),
Triangle, Half Moon, Star, Cushion, Flanders, Asscher, as well as Fantasy
Cuts. Often Colored Stones and increasingly more often, diamonds may be Mixed Cut.
These stones may possess a crown (top) with one cutting style and a pavilion
(bottom) with another. It is the combination of faceting styles which ultimately gives
each stone it's own personality in the form of brilliance (reflected white light) and
dispersion (refracted spectral colors).
The following
diagrams will show many of the variations in cutting styles. Click on the
pictures to see enlarged images.
Diamond
Color
The Diamond Color Scale
The color scale runs the alphabet from D - colorless to
Z - light yellow, brown, or gray color.
D is the rarest color and thus the most valuable.
Diamonds most often form in nature with nitrogen
impurities in their atomic structure.
This causes them to show a subtle tint of yellow color.
As you move down the color scale
the diamonds become more yellow (or brown or gray) and
thus less valuable.
D-E-F Group: Colorless
This diamond group is the rarest and most expensive.
They are common enough to be found
in
many stores, but still command the highest prices. They
show virtually no color.
G-H-I Group: Near
Colorless
This is a very popular color group because of its lower
price, yet they still possess high
enough color to face up reasonably white in a mounting.
Diamonds in the lower end of
this group show a very light shade of color and may
present themselves better in a yellow gold
setting, rather than in white or platinum.
J-K-L-M: Faint Yellow
This is the group that begins to show slight yellow
color.
Slight color may be noticeable from the top of the
stone, but probably more from the sides.
N through R: Very light Yellow
Diamonds in the N-R group show yellow color even when
mounted in jewelry.
Determining the exact color of a diamond in this group
is less important due to the fact that their prices are similar. Certificates for diamonds in
the N-R group are less common
because of
their relatively low price.
S through Z: Light yellow
Diamonds in this group show substantial color when
loose or mounted.
Fancy Colored Diamonds
Fancy Yellow diamonds can command prices as high as D
colors or more.
Colors below the Z range are considered to have color
as an asset and are graded into the fancy color range. The fancy color ranges are as
follows: Fancy Light - Fancy - Fancy Intense - Fancy Deep - and Fancy Vivid. While Fancy Yellow is
more common, Fancy Colored Diamonds can and
do occur in every possible color. Often the color is
described with a secondary mixed color
preceding it.
Ex: Fancy Intense
Orangy-Yellow, with yellow, the second color mentioned, being the predominant
color.
So, to
summarize, there
are Colorless Diamonds (D, E, F), Near
Colorless Diamonds (G,H,I),
progressively off colored diamonds (J-Z), being yellow,
brown, or gray, and Fancy Colored Diamonds.
(click
on the picture to the right to see enlarged view-->)
Fancy Colored Diamonds are not always
"Natural". Their color may have been modified or enhanced
through one or more processes involving irradiation
and/or extreme heat. While this enhancement may
in fact be permanent, the occurrence
of natural color
in diamond is far more rare and thus more
expensive. The tests for identification of "origin
of color" are usually conclusive, but may
require
sophisticated equipment and extremely qualified
testers. It is highly recommended to have
the G.I.A. confirm the origin of color, as natural, in
any fancy colored diamond of enough size to
warrant it.
The Brown Color
Group
Brown diamonds have
a tint of brownish body color. The brown group is usually
less expensive than any other group due to the fact
that they are less appealing to most consumers. In their lightest tones, they
face up reasonably white in a yellow setting. These stones are often described
as "TLB" or Top Light Brown. The brown group is graded by tone, from
light to dark in much the same way as other diamonds, however their appearance
may be slightly whiter than a diamond of slightly yellowish body color, in the
same color grade range. Establishing the correct value with
regard to significantly brown diamonds is difficult. The Argyle mines in Australia
produce a significant quantity of brown diamonds, and have successfully marketed
them using the descriptive names, "cognac" and "champagne".
The common shades are:
Very light brown (champagne), medium brown (champagne),
Brown (dark champagne), and Dark brown (fancy cognac). A color scale has been devised
by the Argyle Mines of Australia for use
in grading these diamonds using C1 - C7 grades to separate them into their progressively darker
tonal ranges.
In spite of the significant marketing efforts of the
Argyle Mines, demand for the brown diamonds is not great and they generally command
relatively low prices.
Fluorescence
 Fluorescence is a phenomenon which causes some diamonds
to glow under ultra violet light (UV), which is abundant in natural daylight and some artificial
lighting.
The following are the possible grades given to
fluorescence:
Faint,
Medium,
Strong,
Very
Strong
All grading reports denote the diamond’s fluorescence
as well as color. It is estimated that 20%-25% of all diamonds have some
degree of fluorescence. Most often diamonds will fluoresce blue, but
occasionally yellow or green or an unusual color may occur.
Strong fluorescence can cause a diamond to look hazy or
less transparent, however this is not always the case. Years ago the term "blue
white" was used to describe the finest of diamonds, many of which had
bluish overtones caused by fluorescence. Unfortunately the term became misused and seldom
accompanied a diamond that was truly white or blue. It is not appropriate to use the expression in
modern times unless the diamond truly possesses a bluish
hue.
Generally speaking, a diamond with strong fluorescence,
sometimes called an over-blue, which diminishes it's brilliance and gives it a sleepy, or
greasy appearance, will cost less than one with faint or no fluorescence. If a diamond is
lightly tinted and has faint to moderate fluorescence, it may face up whiter than another
diamond of similar lightly tinted color possessing no fluorescence, and may actually cost more.
Diamond
Clarity
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IF - INTERNALLY FLAWLESS
- describes
diamonds which have no internal characteristics observable under 10x
magnification, the same conditions as (FL), but which have minor
surface blemishes that do not penetrate the stone. These stones are potentially
flawless if they underwent additional finishing. |
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VVS1 & VVS2 - VERY, VERY SLIGHTLY INCLUDED
-
describes diamonds that have very, very small inclusions which are difficult for a gemologist to see
at 10x magnification. |
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VS1 & VS2 - VERY SLIGHTLY INCLUDED
-
describes
diamonds with very small inclusions which can be difficult to observe with 10x magnification. Inclusions
are not visible to the unaided eye, except on larger stones or occasionally with Emerald
Cut diamonds.
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SI1 & SI2 - SLIGHTLY INCLUDED
-
describes
diamonds with small inclusions which are usually obvious when viewed with 10x magnification. Inclusions are
difficult to see with the unaided eye, except on larger stones or occasionally with Emerald
Cut diamonds. Generally SI1 graded stones are eye clean, while SI2 graded stones may or may not be eye clean.
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I1, I2, & I3
- IMPERFECT -
describes
diamonds with medium to large inclusions (Piques) which are usually obvious to a gemologist with the unaided eye.
An I1 may have an inclusion located to the side while an I2 will have it centrally located or
numerous inclusions.
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Warning - before you
click-
this chart enlarges
to a very large size and may take
a while to open with a slow modem.
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(<--Click
on picture to view enlarged Diamond Clarity Plotting Chart)
This chart represents the plotting of clarity characteristics as they may
appear on a Grading Report from an Independent Lab, such as the Gemological
Institute of America, the Jewelry Industry's foremost leader in Education
and Evaluation of diamonds and colored stones. Generally, internal
characteristics are plotted in red and external (surface) characteristics in
green. The plotting is generally "exaggerated" in size to reflect
the "nature" of the characteristics, and not the relative size.
Even inclusions which are difficult to see under 10x magnification may
appear quite large on the plot, in order to accurately describe the type of
characteristic to anyone viewing the stone and the report. Please
be warned, the enlarged chart is very large and may take a while to open
with a slow modem.
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Diamond
Cut
The various parts
of a diamond are illustrated to the right and below.
(Click on picture below to see enlarged image.)
The
typical faceting style and facet names for the Round Brilliant Cut are
illustrated here. Counting the culet, which is not always actually polished
as a facet, the Round Brilliant has 58 facets. Their exact placement
relative to one  another, as well as the proper angles of their placement,
plays a critical role in the appearance of the finished stone.
Any
diamond which is not "poorly cut" will reflect some of the light
which enters it and disperse some of it, which gives diamonds their unique
brilliance and dispersion. The primary reason for grinding and polishing
facets on a diamond is to enable the light to enter the stone and reflect
back to the viewer in a positive way, thus making the given stone
"marketable". Unfortunately, economics plays a role in the
decision making which directs the size and placement of the facets as well
as the ultimate size and shape of the finished stone.
Ideal Cut
Many
years ago, the "ideal" proportions of a round brilliant cut were
mathematically computed. While these proportions will generate a diamond
with not only
the maximum reflection of light, they also render the ideal balance of 
brilliance (reflected white light) and dispersion (refracted spectral
colors). Unfortunately, the maximum potential weight recovery from the rough
is sacrificed. Modern day diamond cutters attempt to balance these
factors and will most frequently allow popular weight categories that are
targeted as well as increased yield to direct their cutting decisions.
A
diamond which has been cut too shallow will not only reflect less light, 
but
the
lessening of the angles of the pavilion facets will also make the stone
"window" or show a see through effect. This appears to the eye as
if there were dead space instead of sparkle. These diamonds will also often
show an internal reflection of the top of the stone in the bottom, which
resembles a dark circle or "fish-eye".
 A
diamond that has been cut too deep will generally appear dark through the
center.
This occurs because the light is "leaking" through the back of the
stone instead of reflecting back to the eye through the top. Add to this, the
fact that the diameter of the stone, or it's apparent size, is minimized and
you have a smaller facing stone than it's weight would usually render.
The
Ideal Cut, which is illustrated below requires exact placement of facets at
exact angles
relative to one another. They are generally available to a discerning buyer
at a premium over all other diamonds in their class.
A
Premium Cut diamond demonstrates subtle variations from the Ideal Cut.
Although these differences do affect the reflection of light, a Premium Cut
still achieves a harmonious balance between it's proportions and the display
of brilliance and dispersion.
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