Diamonds & DiamondGrading

15
Grading Proportions—
Pavilion and Culet—
and Evaluating Finish
 Table of Contents

Subject Page

The Pavilion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Estimating Pavilion Depth Percentage . . . . . . . . . . . . . . . . . . . . . . . 4
Pavilion Angle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Girdle, Lower Girdle Facets, and Culet . . . . . . . . . . . . . . . . . . . . . . . . 12
Girdle Thickness Percentage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Lower Girdle Facet Percentage . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Culet Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Total Depth Percentage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Design and Craftsmanship . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Relating Weight to Proportions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Finish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Polish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Symmetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Rating Polish and Symmetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Putting it All Together . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Key Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Key Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
©
©2002 The Gemological Institute of America
All rights reserved: Protected under the Berne Convention.
No part of this work may be copied, reproduced, transferred, or
transmitted in any form or by any means whatsoever without the
express written permission of GIA.
Printed in the United States.
Revised and updated 2006
Reprinted 2007

Cover photos: (clockwise from left) Niessing, Ltd., Eric Welch/GIA, John Koivula/GIA, Eric Welch/GIA. Back cover: Glodiam Israel Ltd.

Facing page: The cut of a diamond’s pavilion makes an important contribution to its appearance.
Eric Welch/GIA

GRADING PROPORTIONS—PAVILION
AND CULET—AND EVALUATING FINISH
The transformation of diamond rough into a magnificent gem is a remark- Finish —The quality of the polish
able process. In the hands of skilled cutters, rough crystals become finished and precision of the cut of a
diamonds with dazzling brightness, fire, and scintillation. fashioned gemstone.
A diamond’s cut quality has become increasingly important to diamond
professionals and consumers alike. A knowledge of basic diamond pro-
portions—and how variations in them can impact diamond appearance
and value—will give you an advantage in this rapidly changing segment
of the industry.
The top portion of a round brilliant diamond—its table and crown—
affects how light enters and exits the stone. The diamond’s lower half—
its pavilion—governs the initial path the light takes once it’s inside the
stone. The diamond’s surface appearance and cut precision—its finish—
can make the difference between a diamond that looks lifeless and one
that dances with light and color.

©2002 GIA. All rights reserved. 1

DIAMONDS AND DIAMOND GRADING 15

Both by Eric Welch/GIA

The pavilion (left) plays a central role in a diamond’s appearance because it deter-
mines the path light takes once it’s inside the diamond. Careful planning and skilled
cutting (above) are the keys to a well-proportioned pavilion.

In Assignment 14, you learned how diamond professionals evaluate and

grade a round brilliant diamond’s total depth and upper proportions. In this
assignment, you’ll learn how to assess the rest of the diamond’s features,
including its pavilion, culet, and finish. Whether or not you actually grade
diamonds, knowledge of these procedures is essential. You’ll use this knowl-
edge every day, whether you’re buying, selling, or appraising diamonds.

2
 GRADING PROPORTIONS—PAVILION AND CULET—AND EVALUATING FINISH

Clara Zink/GIA

Peter Johnston/GIA

This assignment will help you evaluate

a diamond’s lower proportions—its
pavilion and culet.

Eric Welch/GIA

Everyone in the diamond trade, including wholesalers in busy diamond bourses

(top) and dealers in New York City’s 47th Street district (bottom), must have
knowledge of diamond proportions to succeed.

3
 DIAMONDS AND DIAMOND GRADING 15

girdle diameter 100%

pavilion depth 44%

pa
vil
ion
an
gle

Peter Johnston/GIA

Diamond professionals describe

pavilion dimensions in two ways,
using pavilion angle and pavilion depth
percentage—a percentage of average
girdle diameter.

The platinum tension setting makes the most of a diamond’s proportions by

exposing the gem to the maximum amount of light.

THE PAVILION
Pavilion depth percentage —The ■ How do variations in pavilion dimensions affect a diamond’s
distance from the girdle plane to appearance?
the culet, expressed as a percent- ■ How are pavilion depth percentage and pavilion angle related?
age of average girdle diameter.
A diamond’s pavilion facets take the light that enters from above and
Pavilion angle—The angle formed reflect it back toward the crown, giving the diamond its spectacular
by the pavilion mains and the brightness. The pavilion is also designed to take advantage of diamond’s
girdle plane. unique ability to break light up into its spectral colors and create fire.
Diamond professionals describe pavilion dimensions in two ways—
pavilion depth percentage and pavilion angle. The pavilion depth per-
centage is the distance from the bottom of the girdle plane to the culet,
Ke y C o n c e p t s expressed as a percentage of the average girdle diameter, which you
learned to calculate in Assignment 14. The pavilion angle is the angle
A diamond’s pavilion makes a signifi-
that’s formed where the pavilion mains meet the girdle plane.
cant contribution to its brightness
and fire.
ESTIMATING PAVILION DEPTH PERCENTAGE
Although you can measure a loose diamond and calculate its pavilion
depth percentage mathematically, estimation is usually accurate enough

4
 GRADING PROPORTIONS—PAVILION AND CULET—AND EVALUATING FINISH

for grading and appraising. The estimation process simply involves iden-
tifying and interpreting the reflections you see through a diamond’s table.
When you look at a round brilliant face-up, the pavilion facets act as
mirrors, reflecting an image of the table. The reflection looks like an
octagonal or circular image that’s centered around the culet, directly
under the table. It can be white, gray, silver, or black.
An easy way to find the table reflection is to look at the diamond face-
up under magnification with darkfield lighting. Rock it back and forth
until the culet appears centered under the table. Look for the dark, trian-
gular reflections of the star facets. Pairs of these reflections look like tiny
black bow ties. They connect together to provide an outline of the table
reflection.
With an exceptionally symmetrical stone, the star facet reflections
might form a complete, continuous outline of the table reflection. But in
The table reflection appears as an
most stones, the star facet reflections are distorted, so you’ll often see image around the diamond’s culet.
only some of them, and they might appear tilted.
Minor cutting variations like misalignment between the crown and
pavilion or even a slightly tilted facet will change the reflection pattern of
the star facets. Even if they form only a partial outline of the table reflec-
tion, they still help you locate it.

Ke y C o n c e p t s
An estimate of a diamond’s pavilion
depth percentage is usually accurate
enough for grading and appraising.

Both by Peter Johnston/GIA

Star facet reflections can help you Star facet reflections rarely form a
locate the table reflection because they perfect outline of the table reflection.
often form a circle around it. Misaligned facets (top) might make some
of the reflections look tilted, and some
might not be visible. Even if they form
only a partial outline (bottom), they can
still help you locate the table reflection.

5
 DIAMONDS AND DIAMOND GRADING 15

TABLE REFLECTION AND PAVILION DEPTH

43.0% 44.5%

A pointer can help you locate the table

reflection. Position its tip at one corner
of the table. You should see its reflec-
tion at the corner of the table reflection
on the opposite side of the stone.

All by Peter Johnston/GIA

To estimate a diamond’s pavilion depth percentage, you compare the size of its
table reflection to the size of the table itself. The smaller the reflection, the lower the
pavilion depth percentage.

You can also use a pointer to locate the table reflection. Under magni-
fication, look at the diamond and position the tip of the pointer at one
corner of the table. You should see the pointer’s reflection on the opposite
side of the table reflection, in the pavilion. The pointer reflection ends at
the edge of the table reflection.
The diamond’s pavilion depth percentage affects how the reflected
image compares in size to the table itself. Once you’ve located the reflec-
tion, determine how much of the space it occupies between the culet and
the table corner. The smaller the reflection, the lower the pavilion depth
To judge the size of the table reflection, percentage. After some practice, you’ll be able to match the reflection
determine how much of it fills the with its corresponding pavilion depth percentage.
area between the culet and the table’s
corner. With pavilion depth percentages of about 43 percent, the table reflec-
tion is fairly small. The edge of the reflection reaches about one-third of
the distance from the culet to the corner of the table. The trade generally

6
 GRADING PROPORTIONS—PAVILION AND CULET—AND EVALUATING FINISH

Both by John Koivula/GIA

If a diamond’s table reflection reaches about halfway from the culet to the table
corner, its pavilion depth percentage is 44.5 percent (left). If the table reflection
reaches more than halfway, its pavilion depth percentage is approximately 45.5
percent (right).

John Koivula/GIA

This diamond’s deep pavilion causes This diamond’s pavilion is so shallow

excessive light leakage, making the that you can see the girdle’s reflection
stone appear extremely dark in the cen- just inside the table facet. This effect is
ter. This is called a nailhead. called a fisheye.

prefers a 43.5 percent pavilion depth percentage, so this is the reflection

you’ll see most often. If the table reflection reaches about halfway from
the culet to the table corner, the pavilion depth percentage is 44.5 percent.
Diamonds with pavilions deeper than 48 percent usually look dark in
the center. At a depth of 50 percent or more, the darkness covers the entire
table and extends out into the star facets. This makes the whole diamond
look very dark. This is called a nailhead.
With pavilion depth percentages under 41 percent, the table reflections
are small, fragmented, and difficult to distinguish. At that point, the girdle
reflection begins to come into view. In round brilliants with pavilions
shallower than 38 percent, the girdle reflection forms an unattractive gray
ring visible just inside the table facet. The effect is called a fisheye, and it
gives the stone a dull, flat look. You might also see a fisheye in stones that
combine a large table with a pavilion depth up to about 40 percent.

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DIAMONDS AND DIAMOND GRADING 15

ESTIMATING PAVILION DEPTH PERCENTAGE

Reflection breaks up

(39.4°) (42.4°)
approx.
Less than 41.0% 45.5%

(40.0°) (43.4°)

42.0% 47.0%
Reflection fills
the table and
looks dark

(40.8°) ( >44.4°)

43.0% 49.0%

Table and star

facets look dark

(41.8°) ( >44.4°)

44.5% Greater than 50%

Peter Johnston/GIA

The size of a diamond’s table reflection is directly related to its pavilion depth
percentage. The corresponding pavilion angles are in parentheses.

8
 GRADING PROPORTIONS—PAVILION AND CULET—AND EVALUATING FINISH

Ke y C o n c e p t s
CULET SIZE AND PAVILION DEPTH
Generally, the greater the pavilion
depth percentage, the steeper the
pavilion angle.

Peter Johnston/GIA

Culet size affects pavilion depth. These two diamonds show the same table reflec-
tion, so you might assume they have the same pavilion depth percentage. However,
the diamond on the right has a larger culet, so its pavilion is shallower.

Culet size can also affect the estimated pavilion depth percentage.
You’ll learn about estimating culet size later in this assignment. Just
remember that as the culet gets larger, pavilion depth gets slightly shal-
lower. So if the culet is large, subtract 1 percent from your estimate of the
pavilion depth percentage; if it’s very large, subtract 2 percent; if it’s
extremely large, subtract 3 percent.

PAVILION ANGLE
Generally, the greater the pavilion depth percentage, the steeper the pavil-
ion angle. The chart on page 10 shows the relationship between these two
parameters.
A pavilion angle that’s extremely shallow (less than 37.4º) or extremely
steep (greater than 44.0º) has a very negative effect on a diamond’s appear-
ance. Steep pavilion angles produce dark areas under the diamond’s table.
Shallow pavilion angles, in combination with large tables and shallow
crown angles, might produce unattractive reflection effects like fisheyes.
Increasing the pavilion angle too much causes light leakage and makes the
center of the stone darker.

9
DIAMONDS AND DIAMOND GRADING 15

Pavilion Depth Percentage and Pavilion Angle

Pavilion Depth % Pavilion Angle
(Approx.)

< 37.5% < 37.0°

37.5% 37.0°
38.0% 37.4°
38.5% 37.8°
39.0% 38.0°
39.5% 38.4°
40.0% 38.8°
40.5% 39.0°
41.0% 39.4°
41.5% 39.8°
42.0% 40.0°
42.5% 40.4°
43.0% 40.8°
43.5% 41.0°
44.0% 41.4°
44.5% 41.8°
45.0% 42.0°
45.5% 42.4°
46.0% 42.8°
46.5% 43.0°
47.0% 43.4°
47.5% 43.8°
48.0% 44.0°
48.5% 44.4°
> 48.5% > 44.4°

Pavilion angle variations can affect a diamond’s appearance. If the pavil-

ion angle varies slightly from main to main, the slight imbalance might
cause some of the returning light to hit the crown outside the critical angle.
Then it will reflect toward the pavilion again instead of leaving through the
crown. This results in uneven brightness and scintillation, which makes the
reflection pattern more difficult to see.
The differences in appearance between diamonds with shallow pavilions
and pavilion angles, and diamonds with deep pavilions and steep pavilion
angles, are obvious to experienced diamond professionals. With practice,
you’ll be able to note those differences, too.

10
 GRADING PROPORTIONS—PAVILION AND CULET—AND EVALUATING FINISH

Diamond Cut Grades and Pavilion Angles

Many pavilion angle ranges overlap from one diamond cut grade to another. For exam-
ple, a diamond with a pavilion angle of 41.4° can fall within any of the GIA cut grades.
However, a diamond with a pavilion angle of less than 38.8° or more than 43.0° falls
outside the ranges for Excellent, Very Good, and Good and can only be Fair or Poor.
Whenever a diamond’s pavilion angle falls outside one or more of the cut-grade ranges,
it eliminates the better grades as possibilities. When you determine the pavilion angle,
round the final figure to the nearest 0.2°.

Possible Cut Grade(s) PA Range PA Comments

P < 37.4° Extremely shallow

F, P 37.4° to 38.6° Very shallow

G, F, P 38.8° to 39.6° Shallow

VG, G, F, P 39.8° to 40.4° Moderately shallow

EX, VG, G, F, P 40.6° to 41.8° Slightly shallow to slightly steep

VG, G, F, P 42.0° to 42.4° Moderately steep

G, F, P 42.6° to 43.0° Steep

F, P 43.2° to 44.0° Very steep

P > 44.0° Extremely steep

PAVILION ANGLE RANGES

40.6° 41.8°
39.8° 42.4°
38.8° 43.0°
37.4° 44.0°
<37.4° >44.0°

11
 DIAMONDS AND DIAMOND GRADING 15

Girdle thickness percentage — GIRDLE, LOWER GIRDLE FACETS, AND CULET

Girdle thickness expressed as a
percentage of average girdle ■ How does girdle thickness percentage affect a diamond’s poten-
diameter. tial cut grade?
■ How do you estimate the length of a diamond’s lower girdle facets?
Lower girdle facet percentage —
The length of the lower girdle ■ What’s the purpose of a diamond’s culet?
facets expressed as a percentage The final calculations needed for determining a diamond’s cut grade are
of the total distance between the girdle thickness percentage, lower girdle facet percentage, and culet size.
girdle and the culet. Girdle thickness percentage is the thickness of the diamond’s girdle
Culet size —The size of the facet expressed as a percentage of its average girdle diameter. Lower girdle facet
at the bottom of the diamond percentage is the length of the lower girdle facets expressed as a percentage
where the pavilion mains meet. of the total distance between the girdle and the culet. And culet size is the
size of the facet at the bottom of the diamond where the pavilion mains meet.

GIRDLE THICKNESS PERCENTAGE

Once you’ve determined a diamond’s pavilion depth percentage, you can
average girdle diameter use that figure to determine its girdle thickness percentage. This parameter
is assessed at the girdle’s thickest areas—the hills—where the bezel facets
meet the pavilion main facets. In Assignment 14, you used the girdle’s
narrowest areas—the valleys—to assess girdle thickness.
girdle To calculate girdle thickness percentage, you need to know the dia-
thickness
mond’s total depth, crown height, and pavilion depth percentages. Simply
add the crown height percentage to the pavilion depth percentage and sub-
tract the result from total depth percentage, then round the final figure to
the nearest 0.5 percent.
For example, you’ve obtained the following parameters for a diamond:
Peter Johnston/GIA

Girdle thickness percentage is a

Total depth percentage: 69.3%
diamond’s girdle thickness expressed Crown height percentage: 14.5%
as a percentage of its average girdle
diameter. Pavilion depth percentage: 43.5%
Girdle thickness percentage = total depth % – (crown height % + pavil-
ion depth %)
GT% = 69.3 – (14.5 + 43.5) = 11.3%
Round the result to the nearest 0.5 percent = 11.5%
Girdle thickness percentage can limit a diamond’s possible cut grade.
If the diamond you’re examining has a very high (greater than 10.0 per-
cent) girdle thickness percentage, you know it belongs in one of the lower
cut grades. Because this diamond’s girdle thickness percentage is 11.5, its
cut grade can only be Poor.

LOWER GIRDLE FACET PERCENTAGE

Lower girdle facets start at the girdle and extend toward the culet. They
occupy a large portion of a round brilliant-cut diamond’s pavilion. Some
in the trade call them lower half facets or lower halves.

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 GRADING PROPORTIONS—PAVILION AND CULET—AND EVALUATING FINISH

LOWER GIRDLE FACET PERCENTAGE

Very short lower girdle

facets ( < 65%)

100% 0%
70%

80%

Very long lower girdle facets

( > 90%)

Peter Johnston/GIA

Lower girdle facet length is stated as a percentage of the total distance between
the girdle and the culet. Long lower girdle facets can work with other parameters to
increase a diamond’s fire.

13
 DIAMONDS AND DIAMOND GRADING 15

To estimate the length of a diamond’s lower girdle facets, hold the dia-
mond girdle-to-girdle in the pavilion-up position. Don’t use a stoneholder, as
it might cover some of the girdle edge and make your estimate less accurate.
Under 10X magnification, examine all eight pairs of lower girdle facets
as you move clockwise around the gem. Consider the distance between
the culet and the girdle as 100 percent. Estimate the distance each lower
girdle facet reaches toward the culet. If it reaches halfway to the culet, the
length is 50 percent; three-quarters of the way, it’s 75 percent; two-thirds
of the way, it’s about 65 percent.
After you have estimates for all the lower girdle facets, average the
results and round that figure to the nearest 5 percent.
If a diamond’s lower girdle facet percentages differ noticeably, the
stone might not be symmetrical. The pavilion might be off-center or the
girdle plane might be tilted. Stones with these characteristics typically fall
into the lower cut grades in the GIA system.

CULET SIZE
The culet is the bottom facet of a diamond, located where the pavilion mains
meet. Its purpose is to prevent abrasion and chipping on loose diamonds. As
you’ve learned, not all diamonds have culets, and many markets actually
prefer diamonds without them.
To determine if there’s a culet, examine the stone face-up at 10X mag-
nification under darkfield lighting. Move a pointer back and forth under
the diamond. If the culet area seems to blink, that means there’s a culet,
and the next step is to determine its size. If the area doesn’t blink, there’s
no culet; if you see a fuzzy white speck, the stone’s point is abraded.
The size of a diamond’s culet limits its possible cut grade. In general,
the larger a diamond’s culet, the lower the cut grade will be. The culet of
a well-cut diamond should be just large enough to prevent abrasion or
chipping before the stone is set. If the culet is too large, it will look like
an unattractive black spot when you look through the table. If the pavil-
ion comes to a sharp, unabraded and undamaged point, the culet might be
described as “pointed.”

Ke y C o n c e p t s
The purpose of a culet is to prevent
abrasion and chipping on loose
diamonds.

Gary Roskin

The culet is located where the pavilion An abraded culet looks like a white,
mains meet. This diamond has a medium fuzzy speck in the center of the
culet. diamond.

14
 GRADING PROPORTIONS—PAVILION AND CULET—AND EVALUATING FINISH

Both by Gary Roskin Eric Welch/GIA

This diamond’s small culet is difficult to This old European cut has a slightly This diamond has a large culet
see at 10X. large culet. that’s visible to the unaided eye.

The culet’s surface should be parallel to the diamond’s table facet. You
assess its angle—if any—by observing the diamond’s profile view. When
the culet is at more than a slight angle to the table facet, consider it an
extra facet rather than a culet and report culet size as “none.”

Estimate culet size by examining the stone face-up under 10X magni-
fication. Look through the table to the place where the pavilion mains
meet. When you classify culet size, use the following descriptions as a
guide:
• None: Absent, or a white abraded or chipped point with no polished
surface at 10X
• Very small: Barely distinguishable at 10X
• Small: Difficult to see at 10X
• Medium: Distinct at 10X
• Slightly large: Obvious at 10X
• Large: Very obvious at 10X
• Very large: Distracting at 10X
• Extremely large: Very distracting at 10X

Include the presence of any clarity characteristics in your assessment.

When there’s a chip, cavity, or indented natural at the culet, consider only
the remaining portion of the culet facet under culet size, and judge the
clarity characteristic in the diamond’s clarity grade.

Sometimes a cutter leaves the culet as an unpolished natural surface. If

it’s nearly parallel to the table facet, consider it a culet and assign the
appropriate size description. The natural is also included in the diamond’s
clarity grade. Abrasion, when present, doesn’t affect culet size, but does
prevent a Flawless clarity grade. It’s also considered as part of the dia-
mond’s polish assessment.

As you learned earlier, a large, very large, or extremely large culet

should reduce your estimate of pavilion depth percentage.

15
 DIAMONDS AND DIAMOND GRADING 15

Thomas Hunn

Shallow macles like these usually yield diamonds with total depth percentages
under 55 percent.

TOTAL DEPTH PERCENTAGE

11.2%
In Assignment 14, you learned to calculate total depth percentage by
using average girdle diameter and total depth in millimeters. If for some
2.0%
reason you can’t measure the diamond directly, you can calculate total
depth percentage by adding crown height percentage, girdle thickness
percentage, and pavilion depth percentage estimates together.
A
41.0%
Examples:
A: crown height percentage = 11.2%
girdle thickness percentage = 2.0%
pavilion depth percentage = 41.0%
17.6%
Total depth percentage = 11.2 + 2.0 + 41.0
4.0% = 54.2%
B: crown height percentage = 17.6%
girdle thickness percentage = 4.0%
B pavilion depth percentage = 46.0%
46.0%
Total depth percentage = 17.6 + 4.0 + 46.0
Peter Johnston/GIA = 67.6%
If you can’t measure a diamond directly, Diamonds with depth percentages greater than about 65 percent often
you can determine total depth by adding
your estimates for crown height, girdle
have steep crown or pavilion angles or thick girdles. On the other hand,
thickness, and pavilion depth percent- depth percentages less than about 55 percent often indicate a thin crown,
ages together. a shallow pavilion, or a thin girdle, all of which are the consequences of
cutting shallow rough. Between these two figures are the proportions that
are considered attractive and marketable by many diamond professionals.
Cutters know, and research shows, that beautiful diamonds come in a
wide range of proportions, and total depth percentage should not be used
as an absolute indicator of a diamond’s appearance. Instead, it’s a guide-
line that represents some of the common proportion combinations seen in
round brilliants. As you’ll learn in Assignment 17, you can also use total
depth percentage to estimate a diamond’s weight.

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 GRADING PROPORTIONS—PAVILION AND CULET—AND EVALUATING FINISH

DESIGN AND CRAFTSMANSHIP Design —A diamond’s physical

shape, including its proportions
■ How do design and craftsmanship influence a diamond’s cut grade? and durability, determined by
■ What affect does excess weight have on a diamond’s cut grade? decisions made during the
fashioning process.
GIA also includes a diamond’s design and craftsmanship in its cut grade.
Design is determined during the fashioning stage. It’s a diamond’s physi- Craftsmanship —The care that
cal shape, including its proportions and durability. Craftsmanship is the goes into the fashioning of a
care that goes into the diamond’s finishing details. polished diamond, as confirmed
by its finish.
Including these factors gives a well-crafted diamond the recognition it
deserves and properly identifies the factors that make it more beautiful
than other diamonds.
Design factors include the diamond’s weight and durability. The GIA
cut-grading system downgrades diamonds that carry excess weight in
extremely thick girdles, steep crowns, or deep pavilions. Diamonds with
features that make them vulnerable to damage—like extremely thin
“knife-edge” girdles—also tend to receive lower GIA cut grades.
The craftsmanship judgment reflects the care taken later in the finishing
process. Ratings for polish and symmetry are included in this category.

RELATING WEIGHT TO PROPORTIONS

A key aspect of the GIA cut-grading system is a determination of the dia-
mond’s weight in relation to its diameter when compared to a 1.00-ct.
reference diamond of standard proportions. Graders call this “weight ratio.”
The standard diameter for a 1.00-ct. round brilliant is about 6.5 mm. If a
diamond with a 6.5-mm diameter weighs 1.20 cts., it’s concealing significant
extra weight.
Some cutters fashion diamonds with hidden weight in extra thick girdles,
steep crowns, or deep pavilions. Diamonds with these features are heavier
than their millimeter diameters suggest. They represent poor value because
a customer pays for extra weight that doesn’t show in the diamond’s face-
up appearance.

Ke y C o n c e p t s
WEIGHT VERSUS DIAMETER Including design and craftsmanship
Excellent to Poor Very Good to Poor Good to Poor Fair to Poor in the cut grade gives a well-crafted
diamond the recognition it deserves.

Diamonds with thick girdles, steep

crowns, or deep pavilions represent
poor value because they appear
< 8% 8% - 16% 17% - 25% > 25%
overweight overweight overweight overweight smaller face-up than their weights
Peter Johnston/GIA suggest.
These diamonds all have the same average girdle diameter, but the cutter added
weight by increasing each one’s total depth.

17
 DIAMONDS AND DIAMOND GRADING 15

Both by Al Gilbertson & Barak Green

These diamonds have the same girdle diameters, and they’d probably appear to be
the same size face-up, but their profiles show very different girdle thicknesses. A
thicker girdle (right) is often used to add weight to a fashioned diamond. It adds to
the total depth percentage without affecting the face-up size.

The difference between an overweight diamond’s suggested weight

and its actual weight can be expressed as its “overweight percentage.”
This percentage can have a negative effect on the diamond’s cut grade.
An excellent way to determine why a diamond is overweight is to
examine its proportions, especially total depth percentage. If a diamond’s
total depth percentage is more than 65 percent, it’s an indication that its
crown, pavilion, or girdle—or all three—are too thick.
On the other hand, if a diamond’s total depth percentage is less than 56
percent, it probably means that some part of the diamond is too shallow.

FINISH
■ What causes some common polish characteristics?
■ What are the levels of polish and symmetry quality?

The details of a diamond’s cut are collectively referred to as its finish.

Finish is made up of two subcategories: polish and symmetry. As you
learned in Assignment 8, polish is the overall condition of the diamond’s
facet surfaces. Symmetry refers to the exactness of the shape and the
placement of its facets.
Eric Welch/GIA You can summarize finish on a customer’s appraisal or report, but for your
This diamond has superior finish, with own records, it’s a good idea to carefully note each polish and symmetry fea-
precisely shaped and placed facets and ture. This will make your records more complete and also help you if you
highly polished facet surfaces.
need to refer to the characteristics of a particular diamond in the future.
Polish and symmetry assessments are based on the degree of visibility
of all the diamond’s variations in face-up and profile views under 10X
magnification.

Ke y C o n c e p t s POLISH
Poor polish can make a diamond A diamond must be well polished to produce sharp reflections and undis-
with even the best proportions look torted light transmission. Poor polish makes stones with even the best
proportions look dull and hazy.
dull and hazy.
18
 GRADING PROPORTIONS—PAVILION AND CULET—AND EVALUATING FINISH

Your Results Might Vary

Valerie Power/GIA

Graders in the GIA Laboratory use complex computer-generated formulas to

grade diamond cut.

As you gain experience with GIA Laboratory cut grades, you might
find that your results differ slightly for certain diamonds. This is a
direct result of the fact that the lab uses complex computer-generated
formulas to calculate some of a diamond’s proportions. This means the
lab’s results can vary slightly from yours, and even slight differences
can affect a final cut grade.
The lab also uses sophisticated instruments to measure a diamond’s
angles. These measuring devices use the table instead of the girdle
plane as a reference when determining crown angles.
The procedures in this course are designed to be practical for use
with the tools most people have available. Quite often, your results
will match the lab’s results. But when they don’t, you should
understand that it’s most likely due to the specialized computers and
instruments that are used in gemological laboratories.

Because of its superior hardness, diamond can take a better polish than
any other gem. Polish characteristics can be a result of the finishing process
or be affected by blemishes created after cutting.

19
 DIAMONDS AND DIAMOND GRADING 15

To evaluate polish, examine the diamond under 10X magnification and

look for surface blemishes that don’t affect the clarity grade. These are
some of those characteristics and their abbreviations:
• Abrasion (Abr): A series of minute nicks along a facet junction,
giving the edges a white or fuzzy appearance.
• Lizard skin (LS): Wavy or bumpy area with a transparent, pitted tex-
Gary Roskin ture, which results from polishing off-grain near a cleavage plane.
• Nick (Nk): A small notch on a facet junction with no readily appar-
ent depth at 10X, usually along the girdle edge or culet.
• Pit (Pit): A small opening that looks like a tiny white dot.
• Polish lines (PL): Fine, parallel grooves and ridges left by the pol-
ishing process. Can appear white (Wht) or transparent (TP), heavy
or light. Heavy polish lines leading from a surface feature, such as
Mitchell Moore/GIA
a cavity, are called drag lines.
• Rough girdle (RG): Irregular or granular girdle surface.
• Scratch (S): A thin, dull, white line across the diamond’s surface,
with no apparent depth.
• Burn mark or burned facet (Brn): Whitish haze across a facet,
caused by excessive heat during polishing or, rarely, by fire from a
jeweler’s torch or other source. A burn mark is sometimes referred
Mitchell Moore/GIA
to as a polish mark (PM).
These three diamonds have abrasions
on their facet junctions, probably
caused by contact with other diamonds.

Mitchell Moore/GIA Gary Roskin

The bumpy areas on the facet surfaces of these diamonds are called lizard skin.

Mitchell Moore/GIA

These diamonds have small notches called nicks on their girdles.

20
 GRADING PROPORTIONS—PAVILION AND CULET—AND EVALUATING FINISH

Gary Roskin Mitchell Moore/GIA

These diamonds both have pits, which look like tiny white dots. One diamond (left)
also has a large scratch.

John Koivula/GIA Mitchell Moore/GIA Mitchell Moore/GIA

These three diamonds have polish lines, which can be white or transparent.

Mitchell Moore/GIA

Mitchell Moore/GIA

An irregular or granular girdle surface is called a rough girdle.

Burn marks are caused by excessive

heat generated during the polishing
process.
Robert E. Kane/GIA Vincent Cracco/GIA

A scratch is a thin white line with no apparent depth at 10X.

21
 DIAMONDS AND DIAMOND GRADING 15

SYMMETRY
Facet diagrams of round brilliants show a precise arrangement of 58 per-
fectly shaped facets. In reality, most diamonds are not cut to such exact
symmetry. Sometimes, facets are distorted or misaligned. The table or
culet might be off-center, or the girdle might look like a warped disk.
Most diamonds have at least a few symmetry variations, but they
typically have little effect on a diamond’s appearance, at least to the
unaided eye.
To evaluate symmetry, you consider the evenness of a diamond’s outline
To assess symmetry, compare facet
sections as you rotate the diamond
and the size, shape, and placement of its facets. Examine the diamond under
360º. On this diamond, the crown and 10X magnification and evaluate each symmetry aspect against an ideal of
pavilion facets are misaligned. absolute perfection. A symmetry rating can range from excellent to poor.
Overall, a round brilliant diamond should look symmetrical. Face-up, a
diamond reveals eight sections. Each section contains a complete bezel and
pavilion main facet and a pair of upper and lower girdle facets. Compare the
sections against each other as you rotate the diamond 360º. All eight sections
should match. If they don’t, the diamond isn’t symmetrical.
For grading purposes, there are two types of symmetry to consider:
proportion symmetry and facet symmetry. Proportion symmetry has to do
with the alignment and balance of the stone’s table, culet, girdle, and
angles, while facet symmetry deals with the shape, placement, and pres-
ence or absence of the facets themselves. Together, these two types make
up the symmetry rating.
Variations in proportion symmetry include:
Peter Johnston/GIA • Out-of-round girdle outline (OR): The girdle outline doesn’t look
A round brilliant diamond should have perfectly round. Might also have a flattened area.
eight matching sections. Each one con-
tains a complete bezel and pavilion • Table off-center (T/oc): The table is not centered in the crown. If a
main facet and a pair of upper and bezel on one side of the crown is longer than the bezel on the oppo-
lower girdle facets. site side, this indicates that the table is off-center.
• Culet off-center (C/oc): The culet is not centered in the pavilion. If
you see more of the pavilion on one side of the culet, this indicates an
off-center culet. If the cross-line formed by the pavilion facet junc-
tions appears bowed or bent, this indicates an off-center culet.

Gary Roskin John Koivula/GIA John Koivula/GIA

This diamond’s girdle outline is notice- An off-center culet can impact a A wavy girdle gives a diamond a
ably out-of-round. diamond’s light performance. warped look.

22
 GRADING PROPORTIONS—PAVILION AND CULET—AND EVALUATING FINISH

• Table/culet alignment (T/C): Table and culet are displaced in oppo-

site directions.
• Wavy girdle (WG): The girdle plane looks wavy rather than flat.
• Table and girdle not parallel (T/G): The table is not parallel to the
girdle plane. Also called tilted table.
• Girdle thickness variation (GTV): Variations in girdle thickness
that, on a brilliant cut, might occur in the areas where crown and
pavilion facets meet.
• Crown angle variation (CV): Variation in measurements of all eight
crown angles on a round brilliant. Typically related to T/oc.
• Pavilion angle variation (PV): Variation in measurements of all
eight pavilion angles on a round brilliant. Typically related to C/oc.
Variations in crown height, pavilion depth, or both, result from a wavy
girdle, a table that’s not parallel to the girdle plane, variation in crown or John Koivula/GIA

pavilion angle, or variation in girdle thickness. Extra facets are typically located on the
pavilion, near the girdle (top). They
Variations in facet symmetry include: might also be found in other locations,
such as the bezel facets (bottom).
• Missing facet (MF): A facet that should be in a given location is
absent.
• Extra facets (EF): Facets not required by the cutting style are
placed without regard for the diamond’s symmetry, most often near
the girdle. They’re considered under symmetry unless they set an
IF clarity grade.
• Table not a regular octagon (T/oct): The table doesn’t have eight
sides of equal length and parallel opposing sides. This results in
star and bezel facets that are also misshapen. John Koivula/GIA

• Misshapen facets (Fac): Facets are not properly shaped, or they’re not This diamond has a non-octagonal
table, with sides that aren’t equal in
the same size and shape as others of the same type. On a brilliant cut, length and opposing sides that aren’t
misshapen facets might be described more specifically as misshapen parallel.
bezel (MB), misshapen star (MS), or misshapen main (MM).
• Non-pointing (Ptg): Facets fail to meet at precise points due to the
presence of an “open” facet, or a fully formed facet doesn’t reach
its prescribed location. On a brilliant cut, Ptg might be described
more specifically as open main (OM), open bezel (OB), short main
(SM), or short bezel (SB).
• Misalignment of crown and pavilion facets (Aln): Crown and pavil- Ke y C o n c e p t s
ion facets not aligned with each other, so the bottom points of the
bezels are not directly above the top points of the pavilion mains,
Most diamonds have some symmetry
and upper girdle facet junctions are not directly above lower girdle variations, but the variations rarely
facet junctions. This might be referred to as “twist” in the trade. affect appearance.
A diamond with variations in alignment probably also has misshapen
facets and pointing. These three variations almost always occur together.
In fact, it’s practically impossible to have one without the others. When
you notice one, check for the other two.

23
 DIAMONDS AND DIAMOND GRADING 15

DIAMOND PROPORTION SYMMETRY VARIATIONS

Out-of-round girdle outline (OR)

Table off-center (T/oc) Culet off-center (C/oc) Culet off-center (C/oc), showing bowed
cross-line

Short bezel
Shaded areas show bezel facets of Shaded area shows more of pavilion on
noticeably different lengths one side of the culet

Table/culet alignment (T/C) Table and girdle not parallel (T/G) Crown angle variation (CV)

Wavy girdle (WG) Girdle thickness variation (GTV) Pavilion angle variation (PV)

24
 GRADING PROPORTIONS—PAVILION AND CULET—AND EVALUATING FINISH

DIAMOND FACET SYMMETRY VARIATIONS

Missing facet (MF) Table not a regular octagon (T/oct) Extra facet (EF)

Non-pointing facet (Ptg)

Misshapen facets (Fac) on crown
misshapen
bezel (MB)
misshapen
star (MS)

Misshapen facets (Fac) on pavilion Misalignment of crown and pavilion (Aln)

misshapen main
(MM)

25
DIAMONDS AND DIAMOND GRADING 15

EXAMPLES OF POLISH CHARACTERISTICS

Transparent polish White polish lines
lines

Scratch

Excellent (Ex) Very Good (VG) Good (G)

Derek Sharpe/GIA Yuen Chan/GIA Mitchell Moore/GIA

Burn marks Extensive burn

on pavilion marks on crown
and pavilion

Fair (F) Poor (P)

Derek Sharpe/GIA Derek Sharpe/GIA

RATING POLISH AND SYMMETRY

There’s no overall grade for finish. On a diamond grading report, graders
rank the stone’s polish and symmetry separately under the “Finish” heading.
For each category, they use the ratings Excellent (Ex), Very Good (VG),
Good (G), Fair (F), and Poor (P).
If polish or symmetry—or both—are rated Excellent, that means
they’re “superior.” It doesn’t mean “perfect,” so a diamond with just a few
very hard-to-find polish lines or some very slightly misshapen facets
could still get an Excellent rating.
If a stone has only faint polish lines or insignificant blemishes, and
very slight misalignment between the crown and pavilion, its polish and
symmetry are Very Good.

26
 GRADING PROPORTIONS—PAVILION AND CULET—AND EVALUATING FINISH

EXAMPLES OF SYMMETRY CHARACTERISTICS

Misalignment Culet off-center
Misalignment

Misshapen
pavilion mains

Misalignment
Excellent (Ex) Very Good (VG) Good (G)

Robert Spencer/GIA Robert Spencer/GIA Robert Spencer/GIA

Non-octagonal Misshapen Out-of-round,

table bezel and with prominent
star facets facet distortions

Misshapen,
short pavilion
mains

Fair (F) Poor (P)

Yuen Chan/GIA Robert Spencer/GIA

A diamond might receive a Good rating if it has transparent polish lines

on the crown that are visible through the pavilion, several small blemishes,
a table or culet very slightly off-center, several extra facets, or noticeable
misalignment between the crown and pavilion.
Obvious polish lines, burn marks, noticeable blemishes, a wavy girdle, a
number of misshapen facets, or noticeable pointing warrant a rating of Fair.
A diamond with a Poor rating usually has either polish characteristics
that reduce transparency or obvious symmetry variations.
Most stones have Good to Very Good polish and symmetry. Cutters
could take the time to give almost any stone Excellent polish and sym-
metry, but they tend to spend more time on large, high-quality stones.
They typically give average-quality or average-sized stones less attention.

27
 DIAMONDS AND DIAMOND GRADING 15

DIAMOND CUT GRADE FACTORS

Diamond Cut Quality

Face-up Appearance Other Contributing Factors

Brightness Design Craftsmanship

Fire
Scintillation

Weight vs. Diameter Polish

Durability Symmetry

Peter Johnston/GIA

The factors that make up a diamond’s cut grade include face-up appearance as well as design and craftsmanship
considerations.

PUTTING IT ALL TOGETHER

■ What factors make up a diamond’s cut grade?
■ What’s the effect of parameters that are at the extremes of their
ranges?

Now that you know the importance of a diamond’s proportions, you

know why a difference of a few degrees or percentage points can affect
the appearance of a stone. You also know that other aspects of a dia-
mond’s cut—like its polish and symmetry—are rarely absolutely perfect.

28
 GRADING PROPORTIONS—PAVILION AND CULET—AND EVALUATING FINISH

After you complete your estimates of the diamond’s proportions, polish,

and symmetry, the next step is to consider them together, along with design
and craftsmanship factors.
The factors to consider are:
• Carat weight compared to average girdle diameter
• Total depth percentage
• Table size and percentage
• Star facet length percentage
• Crown angle
• Crown height percentage
• Girdle thickness
• Girdle thickness variations
• Pavilion depth percentage
• Pavilion angle
• Girdle thickness percentage
• Lower girdle facet length percentage
• Culet size
• Polish and symmetry
These factors all work together to affect a diamond’s appearance. Each Ke y C o n c e p t s
factor limits the diamond’s potential cut grade, and the one that rates the Table percentage, crown angle, and
lowest frequently determines the grade.
pavilion angle play the biggest role
The ranges overlap, and the number of possibilities increases at each
lower cut-grade level. When one parameter falls outside the range of a
in determining a round brilliant
particular cut grade into the level below, the lower level automatically diamond’s brightness.
becomes the highest possible cut grade for that diamond.
For example, if a gem’s total depth is 51.2 percent, its final cut grade
can only be Fair or Poor. In the same way, a girdle thickness of very thin
(VTN) to very thick (VTK) limits a diamond’s cut grade to Good, Fair, or
Poor. If one parameter is lower than all the others, that’s the one that sets
the grade limit. If all of a diamond’s other parameters fit into the Very
Good range, but its polish rates Fair, its highest possible cut grade is
Good.
The proportion factors that play the biggest role in determining a round
brilliant diamond’s brightness are table percentage, crown angle, and
pavilion angle.
Even though the lowest parameter often sets the cut grade, two or more
factors might interact negatively to reduce the cut grade below what you
might expect. Stones with table percentages, crown angles, and pavilion
angles toward the middle of a cut-grade range tend to stay in that grade.
Stones with table percentages or angles toward the extremes of a cut-
grade range tend to receive one or two grades lower.

29
DIAMONDS AND DIAMOND GRADING 15

56%

37.0°

44.0°

This stone’s extremely steep pavilion angle (left) produced a very distracting dark
area under the table facet. It’s called a dark center (right). It has a negative effect on
the stone’s appearance, resulting in a Poor cut grade.

59%
26.0°

38.6°

This diamond has a slightly large table (left), but when combined with shallow
crown and pavilion angles, the result is an extreme fisheye effect (right). This combi-
nation resulted in a Fair cut grade.

63%
32.0°

41.0°

Peter Johnston/GIA Eric Welch/GIA

This diamond has a moderately large table (left). Its combination of slightly shallow
crown and pavilion angles and long star and upper girdle facets create strong fire
(right) and a Very Good cut grade.

A diamond might have parameters—including table percentage (62.0

percent), crown angle (36.0º), and pavilion angle (41.6º)—that fall into
the Excellent ranges, but a visual estimate of its cut might limit its grade
to Very Good. In this instance, the interaction of these parameters lowers
the grade from what you’d expect if you considered them separately.

30
 GRADING PROPORTIONS—PAVILION AND CULET—AND EVALUATING FINISH

Excellent (Ex) Ke y C o n c e p t s
58%
It’s important to place more
Table %

emphasis on the way a diamond

actually looks than on its numerical
52% minimum 62% maximum parameters.
33.5°
Crown
Angle

31.5° minimum 36.5° maximum

41.2°
Pavilion
Angle

40.6° minimum 41.8° maximum

This diamond’s table percentage, crown angle, and pavilion angle are well within
Excellent ranges, so the diamond is solidly in the Excellent cut grade.

Very Good (VG)

61%
Table %

52% minimum 62% maximum

36.0°
Crown
Angle

31.5° minimum 36.5° maximum

41.6°
Pavilion
Angle

40.6° minimum 41.8° maximum

Both by Peter Johnston/GIA

This diamond’s table percentage, crown angle, and pavilion angle are all close to
the limits of the Excellent cut grade range. This combination reduces brilliance and
fire enough to drop the grade of this stone to Very Good.

It’s important to place more emphasis on the way a diamond actually

looks than on its numerical parameters. This is because the interaction of
two unfavorable angles might give a diamond a dark pattern or other unat-
tractive feature. On the other hand, many stones with unconventional
angles are more attractive than their numbers suggest.

31
 DIAMONDS AND DIAMOND GRADING 15

CUT SUPPLEMENT
Cut Grade Reference Chart
Excellent Very Good
Brightness High (stone appears very bright) High to moderate (stone appears bright)

Fire High High to moderate

Pattern Only minute pattern defects; even pattern Minor pattern defects; slight darkening of
of bright and dark areas with strong con- pavilion mains and along upper girdle facets
trast; symmetrical pattern of dark radiating
mains permitted within the table facet if
the area around the culet remains bright

Total depth % 57.5% to 63.0% 56.0% to 64.5%

Table % 52% to 62% 50% to 66%

Crown angle 31.5° to 36.5° 26.5° to 38.5°

Pavilion angle 40.6° to 41.8° 39.8° to 42.4°

Crown height % 12.5% to 17.0% 10.5% to 18.0%

Star facet length % 45% to 65% 40% to 70%

Lower girdle facet % 70% to 85% 65% to 90%

Girdle thickness Thin to Slightly Thick Extremely Thin to Thick

Culet size None to small None to medium

Polish Excellent to Very Good Excellent to Good

Symmetry Excellent to Very Good Excellent to Good

Note: Some table percentages, crown Note: Some table percentages, crown angles,
angles, and pavilion angles within the and pavilion angles within the ranges for Very
ranges for Excellent might combine to Good might combine to negatively affect the
negatively affect the grade and reduce it grade and reduce it to Good or lower.
to Very Good or lower.

This chart gives the proportion ranges for each GIA cut are close to their respective limits, they’ll probably
grade. Remember that the cut grader considers a dia- reduce the stone’s cut grade.
mond’s proportions together as well as individually.
Also, the factor that grades lowest is the one that
That’s because even though a gem’s parameters might
determines the maximum possible cut grade.
all be within limits for a particular cut grade, it might
actually grade lower because they interact in a negative Finish—polish and symmetry—also affects the
way. Table percentage, crown angle, and pavilion angle gem’s cut grade, but a diamond’s polish and symmetry
are especially critical. If two or more of these parameters can be one grade lower than its cut grade.

32
 GRADING PROPORTIONS—PAVILION AND CULET—AND EVALUATING FINISH

Good Fair Poor

Moderate (stone appears quite Moderate to low (stone appears gener- Low (stone appears very dark with few
bright, with some dark areas) ally dark, with some bright areas) bright areas)

Moderate Moderate to low Low; very little visible fire

Noticeable pattern defects; dark Obvious pattern defects; fisheyes give Prominent pattern defects; very dark
pavilion mains extend under the general “grayed-out” appearance; lack areas under the table (nailheads); very
crown facets and distract from of contrast between light and dark dark upper girdle facets; extremely dark
appearance; slight dark rings areas; very dark upper girdle areas; pavilion mains; patterns lack contrast
within table facets; somewhat general darkness under table; very dark and might appear very “blocky”
dark upper girdle facets radiating mains

53.0% to 66.5% 51.0% to 70.9% <51.0% to >70.9%

47% to 69% 44% to 72% <44% to >72%

22.0° to 40.0° 20.0° to 41.5° <20.0° to >41.5°

38.8° to 43.0° 37.4° to 44.0° <37.4° to >44.0°

9.0% to 19.5% 7.0% to 21.0% <7.0% to >21.0%

Any value Any value Any value

Any value Any value Any value

Extremely Thin to Very Thick Extremely Thin to Extremely Thick Extremely Thin to Extremely Thick

None to large None to very large None to extremely large

Excellent to Fair Excellent to Fair Excellent to Poor

Excellent to Fair Excellent to Fair Excellent to Poor

Note: Some table percentages, Note: Some table percentages, Note: The presence of any one extreme
crown angles, and pavilion angles crown angles, and pavilion angles proportion element, girdle thickness, or
within the ranges for Good might within the ranges for Fair might Poor finish rating establishes cut grade
combine to negatively affect the combine to negatively affect the as Poor.
grade and reduce it to Fair or Poor. grade and reduce it to Poor.

Check the profile for hidden Check profile for extra hidden weight Check profile for extra hidden weight or
weight. or “knife-edge” girdle. thin crown with “knife-edge” girdle.

The descriptions of brightness and fire for the Good Symbols:

and Fair grades represent general impressions because When followed by a quantity or percentage,
a wide variety of appearances are possible. Some
stones with excellent brightness might grade Good or > means “greater than”
Fair because they lack fire or display unattractive pat-
< means “less than”
terns. Similarly, some stones that show high levels of
fire but low levels of brightness might grade Good or
Fair as a result.

33
DIAMONDS AND DIAMOND GRADING 15

New GIA Diamond Grading Reports

With the launch of the new cut grade, the GIA
Laboratory also redesigned its diamond reports
to make them easier to understand at a glance.
All the major “4Cs” grading information is in
a colored panel in the middle of the report.
Both the full report and the Diamond
Dossier®—a shorter report for diamonds of
0.99 ct. or less—have similar formats. On
both reports, the grading information is
arranged into three sections.
The top section includes the diamond’s
laser inscription number, shape, and basic
measurements—the minimum and maximum
diameters and depth in millimeters.
The center section presents grading results
based on the 4Cs: carat weight, color, clarity,
and cut. Across from this section, graphics
illustrate the GIA color, clarity, and cut scales.
Directly beneath the 4Cs there’s additional
information, including finish—polish and
symmetry—fluorescence, and comments.
Under the grading information on the full
report, a plot documents the location and
extent of important clarity features.
Each report type includes a scaled profile
that displays all of the diamond’s essential
proportions. The profile acts as a “blueprint”
for the individual diamond.
All proportion information is repeated on the
report flap. Most dealers remove this tear-off
portion and keep it for their inventory records.
The full GIA diamond report
includes a plot of the diamond.

34
 GRADING PROPORTIONS—PAVILION AND CULET—AND EVALUATING FINISH

The Diamond Dossier is an abbreviated report designed for diamonds under

0.99 ct.

The back of the GIA

diamond report
cover contains brief
descriptions of the
Four Cs.

35
DIAMONDS AND DIAMOND GRADING 15

Ke y C o n c e p t s
A diamond’s pavilion makes a significant contribution to its Poor polish can make a diamond with even the best
brightness and fire. proportions look dull and hazy.

An estimate of a diamond’s pavilion depth percentage is Most diamonds have some symmetry variations, but the
usually accurate enough for grading and appraising. variations rarely affect appearance.

Generally, the greater the pavilion depth percentage, the Table percentage, crown angle, and pavilion angle play the
steeper the pavilion angle. biggest role in determining a round brilliant diamond’s
brightness.
The purpose of a culet is to prevent abrasion and chipping
on loose diamonds. It’s important to place more emphasis on the way a diamond
actually looks than on its numerical parameters.
Including design and craftsmanship in the cut grade gives
a well-crafted diamond the recognition it deserves.

Diamonds with thick girdles, steep crowns, or deep pavilions

represent poor value because they appear smaller face-up
than their weights suggest.

36
 GRADING PROPORTIONS—PAVILION AND CULET—AND EVALUATING FINISH

Key Terms
Craftsmanship—The care that goes into the fashion- Lower girdle facet percentage—The length of the
ing of a polished diamond, as confirmed by its finish. lower girdle facets expressed as a percentage of the
total distance between the girdle and the culet.
Culet size—The size of the facet at the bottom of the
diamond where the pavilion mains meet. Pavilion angle—The angle formed by the pavilion
mains and the girdle plane.
Design—A diamond’s physical shape, including its
proportions and durability, determined by decisions Pavilion depth percentage—The distance from the
made during the fashioning process. girdle plane to the culet, expressed as a percentage
of average girdle diameter.
Finish—The quality of the polish and precision of the
cut of a fashioned gemstone.

Girdle thickness percentage—Girdle thickness

expressed as a percentage of average girdle
diameter.

37
DIAMONDS AND DIAMOND GRADING 15

ASSIGNMENT 15

QUESTIONNAIRE

Each of the questions or incomplete statements below is followed by several possible answers. Choose
the ONE that BEST answers the question or completes the statement. Then place the letter (A, B, C, or D)
corresponding to your answer in the blank at the left of the question.
If you’re unsure about any question, go back, review the assignment, and find the correct answer. When
you’ve answered all the questions, transfer your answers to the answer sheet.

________1. If a diamond’s pavilion depth percentage is 39.0 percent, its pavilion angle is
approximately
A. 37.8º
B. 38.0º
C. 38.4º
D. 38.8º

________2. As a diamond’s pavilion gets deeper, its table reflection becomes

A. larger.
B. lighter.
C. smaller.
D. more difficult to see.

________3. If a diamond’s culet is too large, it will look like

A. a small cavity.
B. an indented natural.
C. a fuzzy, white speck.
D. a black spot under the table.

________4. Which of the following pavilion depth percentages would most likely cause the girdle
reflection to be visible face-up through the table?
A. 37.0%
B. 42.0%
C. 45.0%
D. 48.0%

CONTINUED NEXT PAGE...

IF YOU NEED HELP: Contact your instructor through GIA online, or call 800-421-7250 toll-free in the US and Canada, or 760-603-4000;
after hours you can leave a message.

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 GRADING PROPORTIONS—PAVILION AND CULET—AND EVALUATING FINISH

________5. The care that goes into the fashioning of a polished diamond, as confirmed by its finish,
is its
A. cut.
B. shape.
C. polish.
D. craftsmanship.

________6. Calculate an estimated total depth percentage for a round brilliant diamond with the
following proportions:
Crown height percentage: 12.5%
Girdle thickness percentage: 3.0%
Pavilion depth percentage: 43.0%

A. 58.5%
B. 59.0%
C. 58.0%
D. 59.5%

________7. The purpose of the culet facet is to

A. prevent chipping.
B. improve symmetry.
C. maximize brilliance.
D. maximize light leakage.

________8. The proportions that play the biggest role in determining a round brilliant diamond’s
brightness are table percentage, crown angle, and
A. culet size.
B. pavilion angle.
C. crown height percentage.
D. girdle thickness percentage.

________9. Calculate an estimated total depth percentage for the following stone:
Average girdle diameter: 4.45 mm
Crown height percentage: 15.5%
Girdle thickness percentage: 7.0%
Pavilion depth percentage: 45.5%

A. 67.0%
B. 67.5%
C. 68.0%
D. 68.5%

CONTINUED NEXT PAGE...

39
DIAMONDS AND DIAMOND GRADING 15

________10. Large, very large, or extremely large culets should be considered when determining
A. polish.
B. clarity.
C. symmetry.
D. pavilion depth percentage.

________11. Which of the following is part of an evaluation of proportion symmetry?

A. Scratches
B. Wavy girdle
C. Rough girdle
D. Non-pointing facets

________12. A diamond with variations in alignment probably also has

A. polish lines.
B. misshapen facets.
C. a low clarity grade.
D. an out-of-round girdle outline.

________13. A diamond with a thick girdle, steep crown, or deep pavilion represents poor value
because
A. it doesn’t look attractive.
B. it can’t be set into a jewelry piece.
C. it appears smaller face-up than its weight suggests.
D. its proportions create durability problems in the polished stone.

________14. A diamond’s physical shape, including its proportions and durability, determined by
decisions made during the fashioning process, is its
A. finish.
B. polish.
C. design.
D. brilliance.

________15. Most diamonds have some symmetry variations

A. that affect the value of the stone.
B. but they rarely affect appearance.
C. that appear both obvious and distracting.
D. but they don’t need to be evaluated when grading.

40
 GRADING PROPORTIONS—PAVILION AND CULET—AND EVALUATING FINISH

PHOTO COURTESIES
The Gemological Institute of America gratefully acknowledges the following people and organizations for their assistance in
gathering or producing some of the images used in this assignment:
Field’s Jewelers, 20 (bottom left)
Hasenfeld-Stein, 1, 2 (right)
Israel Diamond Exchange, 3 (top)
Niessing, Ltd., 4

41
 1. Introduction: Beyond the Essentials

2. Birth of the Modern Diamond Industry

3. The Modern Diamond Market

4. How Diamonds Form

5. Exploring for Diamonds

6. Diamond Mining

7. The Diamond Crystal

8. Diamonds and Light

9. The Evolution of Diamond Cutting

10. Finding and Identifying Clarity

Characteristics

11. Grading Clarity

12. Diamonds and Color

13. Grading Color

14. Grading Proportions—Table, Crown,

and Girdle

7/2007
15. Grading Proportions—Pavilion and
Culet—and Evaluating Finish

16. Grading Fancy Cuts

17. Estimating Weight, Recutting, and

Repolishing

18. Diamond Simulants

19. Synthetics and Treatments

20. Succeeding in the Marketplace