In 1939 Robert Shipley and Richard Liddecoat went about
creating a method of grading a diamonds quality consistently through scientific
evaluation. The process they created became the foundation for the internationally
accepted and uniformly practiced diamond grading method. Diamonds are examined
for their relative purity, or clarity, and the color the stone has by
determining it's depth and hue. There are 11 clarity grades and letter assigned
color grades from D to Z.
Diamonds form 90 to 120 miles below the earth's surface in
the upper mantle. Due to the chaotic nature of these deep earth conditions as
diamond crystals form some foreign elements can find their way into the growth
process and become trapped within the stone. These elements become known as
inclusions and they are what gemologists examine when determining the clarity
of a diamond. Clarity is determined by the inclusion's size, number, position,
nature and relief and given a grading as follows:
Flawless (F) - No inclusions or external blemishes are visible at 10x magnification.
Internally Flawless (IF) - No inclusions and only very minor external blemishes under 10x magnification.
Very Very Slightly Included (VVS1-VVS2) - Inclusions within the diamonds are extremely difficult to see with 10x magnification. In VVS-1 stones they can only be seen through the diamonds pavilion, appearing flawless from the face up view.
Very Slightly Included (VS1-VS2) - Inclusions are very difficult to difficult to see under 10x magnification.
Slightly Included (SI1-SI2) - Inclusions are somewhat noticeable under 10x magnification, and in some cases can be visible without magnification.
Included (I1-I3) - These are diamonds with obvious inclusions under 10x magnification and can be visible without the aid of a loupe or microscope, in I-2 and I-3 diamonds inclusions can cause a durability issue for the diamond.
Number designations of these clarity grades (i.e. VS-1;VS-2) indicate a higher
and lower classification to each grade with the exception of the flawless categories.
F and IF
A diamonds color is commonly
caused by nitrogen becoming absorbed in the crystal during the formation
stages. The nitrogen then absorbs a trace amount of color in the visible light
spectrum and to varying degrees this causes a diamond to display a slight tint
of color. Prior to the current color grading method a confusing system of
letter grades using A, B and C was in place, hence the GIA scale begins with
the letter D and goes through to Z. Each letter represents a range of known
diamond color based on color comparison stones starting at colorless and
gradually becoming more saturated with a visible color. The color grading is as
Very Light Color
D, E, F - Colorless - These are diamonds displaying no color, and are graded according to their level of transparency.
G, H, I, J - Near Colorless - These are diamonds displaying a very slight tint of color that is not very noticeable appearing colorless face up.
K, L, M - Faint Color - Diamonds that display a slightly more noticeable tint than the near colorless stones.
N through R - Very Light Color - Diamonds of this grade display noticeable color.
S through Z - Light Color - Obvious color noticeable to an untrained eye.
Colors beyond Z are considered Fancy color, and are graded
based on their hue, depth and saturation of color. Diamonds that display colors
other than yellow and brown (i.e. blue, pink, green) are considered fancy
without this letter system. The fancy color grading system ranges from fancy
faint, fancy light, fancy, fancy intense, fancy vivid, fancy deep and fancy
The evolution of diamond cut has been a process in the
making for hundreds of years. Since diamond is the hardest element ever found
it presents a challenge for diamond cutters to produce a beautiful polished
gem. Remember only a diamond can cut a diamond, and with that fact special
tools have been designed to facilitate cutting the hardest material known to
The round brilliant shape has been the one with the most research done
as far as how to bring out the maximum brilliance and fire in the stone. Depth
percentage is the ratio between the diamonds diameter and depth measurements,
expressed as a percentage this is what tells gemologists how well the diamond
will return light to the eye.
Ideal or Premium cuts have depths that ensure the
proper angles of reflection occur within the stone so that light entering the
diamond through the crown gets returned to the eye. The best way to think of it
is as windows and mirrors. The crown facets act as the window, allowing light
to enter and exit the diamond while the pavilion acts as the mirrors reflecting
this light so it returns through the top.
Different diamond cuts do different
things with light, and as of right now there is no Ideal cut diamond when it
comes to fancy shapes, although gemological institutions are working on
developing a method of evaluating cut on shapes other than round.
We are using our own cut quality tables
to evaluate cut quality of various diamond shapes.
Carat is the measurement of weight used primarily for
diamonds and other gemstones when determining price. In ancient times diamonds
and other precious gemstones were weighed on balance scales with the
counterweights being carob seeds, this is where the word carat is derived. One
carat is equal to 200 milligrams or about one fifth of a gram, this measurement
is divided into "points" from one point (0.01ct) to ninety nine points (0.99ct)
with each weighing 2 milligrams.
A one carat round diamond with good
proportions should measure about 6.50 millimeters in diameter indicating a
correlation between the visual size as well as the weight. A diamond is equated
at a "per carat" price that is multiplied by the weight to determine the
overall cost of the stone.
Diamond's Polish and Symmetry
Polish and symmetry is evaluation of the finished surface
on a polished diamond and are rated on a scale from excellent to poor.
They are graded under the same 10x magnification standards as clarity and have
some moderate effect on the overall price. Stones that have a polish and
symmetry of Good, Very Good or Excellent are of a choice
quality where great care and expertise went into the finishing of a polished
Fluorescence is a natural occurrence in some diamonds when
exposed to ultraviolet light sources where the diamond appears to glow. The GIA
reports that nearly a third of all diamonds graded in their lab every year
display fluorescence to some degree. It is rated under long wave ultraviolet
light and reported as None, Faint, Medium or Strong.
More often the fluorescence appears blue, but can appear as white or yellow as
well. The Hope Diamond has a red fluorescence which is considered to be a very
rare, as well as a phosphorescence where it continues to glow up to fifteen
minutes after the UV light source has been removed which is also an extremely
rare and fascinating occurrence.