JThomson Custom Jewelers
Diamond
Cut
The cut is
the most important characteristic of a diamond. When you see diamonds selling
for prices that are too good to be true, it is usually because they are cut
poorly.
How well a
diamond is cut determines how much of the light that enters a diamond is reflected
back out of the top of the gem, and hence how much sparkle you see. If a diamond
is cut poorly, the light entering the diamond from above will reflect out the
sides and bottom, and the stone will look dead – there will be no sparkle
and fire, regardless of the color or clarity
of the stone.
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Shallow Cut
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Ideal Cut
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Deep Cut
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Many diamonds
are cut poorly. This is because a cutter can often get more weight (and therefore
a higher price) out of a rough diamond by taking shortcuts in the proportions
of the stone. In the best-case scenario, approximately 50% of the weight is
lost from the original crystal in the cutting process. Because size is important
to many consumers, often cutters sacrifice diamond beauty in order to save weight,
maximizing the size of the finished diamond. Note that cut is also referred
to as make.
To make it
easier to judge the cut, we classify diamonds into different categories. Very good cut diamonds
are exceptionally proportioned "investment quality" stones that reflect
back as much as 90% of the light entering the diamond from above. The very best
of the round diamonds are called "ideals"."Good"-rated diamonds
are also well proportioned stones that make fantastic jewelry because of their
ability to reflect light. Fair and Poor-cut diamonds are less
well proportioned, and therefore are generally less expensive. These stones
can reflect as little as 40% of the light entering the stone back out of the
table. It is usually worth the money to buy a Very Good or Good-cut diamond,
even if it means buying a smaller stone, or one with lesser color and clarity
grades.To determine how well cut a diamond is, all you need to do is examine
a couple grades on the certificate: depth percentage (the height
versus the width of the stone) and table percentage (how large
the very top of the stone is versus the width). In addition, you will want to
make sure that the polish, symmetry, girdle,
and culet fall within acceptable standards.
This sounds
harder than it really is! To see if a round diamond is well cut, just compare
the diamond’s certificate to the following chart:
Proportion
Guidelines for Round Diamonds:
You may also view
an illustration of these characteristics.
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Ideal
Proportions
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Acceptable
Proportions
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Unacceptable
Proportions
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| Depth: |
60.2%
- 62.7%
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57.0%
- 64.0%
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Less
than 57.0% or greater than 64.0%
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| Table: |
53.0%
- 57.0%
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53.0%
- 64.0%
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Less
than 53.0% or greater than 66.0%
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| Polish: |
Very
good to excellent
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Good
to excellent
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Poor
to fair
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| Symmetry: |
Very
good to excellent
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Good
to excellent
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Poor
to fair
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| Girdle: |
Thin
to medium
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Thin
to thick
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Very
thin or very thick
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| Culet: |
None
to very small
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None
to medium
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Medium
to large
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There are
also proportion guidelines for diamonds of other shapes. To see these, click here.
Optical Beauty:
The way a diamond reflects and refracts light is dazzling to the beholder. There
are four factors that determine the optical beauty of a diamond: luster, brilliance,
dispersion, and scintillation.
- Luster - The quantity
and quality of light reflecting from the surfaces of a diamond.
- Brilliance - The amount
of white light returned to the eye from the diamond.
- Dispersion - The amount
of rainbow colors returned to the eye from within the diamond.
- Scintillation - The sparkle,
which is the combination luster, brilliance, and dispersion when there is
movement by the wearer or light source.
