How To read a
Diamond Certificate
The beauty of a diamond
can only be truly appreciated when it is viewed in person under proper
lighting. However, with certification, we can now guarantee the quality
of the gemstone you purchase. Of course, selecting the very best is easy
with an unlimited budget, but selecting the diamond which is the best compromise
of the four quality factors (Color, Clarity, Cut, Carat weight), and price
involves more thought. By understanding how expert gemologists judge the
quality of gemstones using certification, you can better understand what
compromises you are willing to make in the final selection. This information
on how to read a diamond certificate will help you make these decisions.
This
document contains many sections. We suggest you read the document through
once, and then use these links to take you to the area of interest as needed.
Shape and Cut
- Refers to the style and make of the diamond. The style is the shape of
the stone; for example: round brilliant, marquise shape, oval shape, emerald
cut, princess cut, radiant cut, heart shape, and baguettes. Many believe
the larger the diamond the greater its value. This is not necessarily true.
It is the cut that unlocks the beauty for which diamonds are valued. Larger
diamonds are generally full cut, meaning they have 58 facets, each of which
must be in precise symmetrical relationship. The responsibility for this
precision lies solely with the cutter. (top)
Measurements
- When measuring the diameter of a round diamond, the circumference and
the depth of the stone are gauged. These measurements are then used to
calculate the proportions of the diamond. On fancy shaped diamonds the
measurements are taken length by width. (top)
Weight
- Carat or carat-weight refers to the size and weight of the diamond. The
word carat originated from times when the seeds of the carab tree were
used on a balance scale to measure weight. Today, the standard weight of
one carat is 0.2 grams or 1/5 of a gram. One carat is divided into 100
points; a diamond of 75 points weighs 0.75 carats. A large diamond is not
necessarily a better or more valuable diamond. Two diamonds of equal weight
can have very unequal value, depending on their cut, color and clarity.
(top)
Proportions
- ratio of two specific measurements of a diamond. This relationship is
an indicator of the diamond's brilliance. (top)
Depth
- Refers to the total depth of the stone from the table, or top, of the
diamond to the culet, or point. In round brilliants the range of generally
accepted depth to width ratio is between 57% and 63%. (Ideal proportions
are 58.9% to 61.8%.) In fancy shapes, the total depth and other proportions
are not scrutinized the same way as round brilliants. (top)
Table
- The table is the largest facet of the diamond and considered the window.
In round brilliants, the range of generally accepted table to overall diameter
is 53% to 66%. (Ideal proportions are 53% to 57%.) Again, in fancy shapes,
the table diameter and other proportions are not scrutinized in the same
way as in round brilliants. (top)
Girdle
- Refers to the middle of the diamond that separtes the crown, or top of
the diamond from the pavilion, or bottom. The girdle generally makes up
to 2%to 3% of the total depth of the stone. This can vary depending on
how thin or thick the girdle actually is. Some girdles are faceted and
others are granular and have a frosted appearance.
Culet
- The culet is a polished facet placed at the tip of the diamond to prevent
chipping. The culet ranges from none or white abraded to extremely large,
which would show an octanganal outline when looking through the stone.
The culet is graded through the table, with the stone face up, under 10X
magnification. (top)
Polish
-The polish grading rates the surface of the diamond. This includes blemishes
which are surface characteristics such as: abrasions, nicks, pits, polish
lines, polish marks, a rough girdle, and scratches. (top)
Symmetry
- This indicates how symmetrical and aligned the facets of the diamond
are to one another. Factors that can affect the symmetry include the following:
off center culet or table, out of round girdle, facets that fail to point
properly, misalignment of crown and pavilion facets, a table that is not
a rectangular octagon, misshapen facets, table and girdle not in parallel,
a wavy girdle, a natural (a rut that can affect the clarity grade) or extra
facets (which do not affect the clarity grade). Polish and symmetry are
given the grades of Excellent, Very Good, Good, Fair, and Poor. (top)
Clarity Grade
- Clarity refers to minute traces of non-crystallized carbon, called inclusions.
Almost all diamonds have inclusions, though most are not discernable to
the eye without aid of magnification. The fewer inclusions there are, the
rarer the stone will be. As with color, we use the GIA scale for grading
clarity. There are eleven clarity grades used by a skilled grader at 10X
magnification to evaluate and determine the various clarity characteristics.
(top)
Flawless (FL)-A
flawless diamond shows no blemishes or inclusions. The following do not
disqualify a diamond from the flawless category:
-
an extra facet on the
pavilion which cannot be seen face up
-
naturals totally confined
to the girdle (which neither thickens nor distorts its outline)
-
internal graining marks
which are not reflective, white, or colored and do not significantly affect
the transparency of the diamond.
Internally
Flawless(IF)-An internally flawless diamond shows no inclusions and has
only insignificant blemishes.
Very Very Slightly
Included (VVS1 and VVS2)- A VVS diamond contains minute inclusions that
are extremely difficult to locate. VVS1 differs from VVS2 in that the the
inclusion can only be seen through the pavilion.
Very Slightly Included
(VS1 and VS2)-VS diamonds contain minor inclusions ranging from difficult
to see (VS1) to somewhat easy to see (VS2).
Slightly Included-An
SI diamond contains noticable inclusions which would be easy to see (SI1)
to very easy to see (SI2). In some SI stones, inclusions are visible to
the unaided eye.
Imperfect (I1,I2,
and I3)- An imperfect diamond contains inclusions which are obvious and
can easily be seen face up. In I2 and I3 diamonds the inclusions are usually
so numerous that they can affect the transparency and brilliance of the
diamond and can also pose a durability threat. Some certs use the term
Pique (P1,P2, and P3) in place of imperfect. (top)
Please note: The previous
clarity descriptions are most applicable to round brilliants and some characteristics
may be more visible in large stones and fancy shapes.
Color Grades
- Refers to color, or, more accurately, the absence of color. Most diamonds
have color. Those without color are rare and so premium priced. A tinge
of color is evident in most diamonds with some having a body color slightly
more visible. It is important to note that these types of diamonds cost
less than totally colorless diamonds because they they are less rare, not
because colorless is better. In fact, a diamond with a tinge of color can
hold greater appeal than icy white diamonds. To help determine the differences,
the Gemological Institute of America (GIA) created a scale with colorless
diamonds starting at 'D'. D, E , and F are considered colorless. G, H,
I and J are near colorless which is still considered white. With the descending
letters (K, L, etc.) the color becomes more intense. (top)
Flourescence
- Ultraviolet flourescence is an emission of visible glow stimulated by
invisible wavelengths. Approximately 50% of all gem quality diamonds exhibit
some degree of flourescence. Diamonds can flouresce any color; the most
common color is blue. The strength of flourescence is described in the
following terms:
-
None - also known as
inert
-
faint - occurs just
around the girdle's edge
-
Moderate - the majority
of the body glows, but not strongly
-
Strong - the whole stone
glows brightly (top)
Comments
- This section contains any other points not already listed on the diamond
report. (top)
Diagram
- The diagram is the blueprint of the diamond. The diamond is plotted with
different symbols for the different characteristics. Red is used for those
that are internal and green for external. The first symbol listed in the
key is usually the clarity grade setter or the most visible inclusion.
Plotting is done to identify the diamond and document the condition and
characteristics of it; plotting also serves to support and justify the
clarity grade. (top)