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Gemmology > Chapter 12 > Flashcards

Chapter 12 Flashcards

1
Q

What is the effect of light on a diamond’s appearance?

A

Every angle and facet affects the amount of light returned to the eye

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2
Q

What three qualities are assessed when estimating the cut of a polished round brilliant diamond?

A

Brightness, fire, and scintillation

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3
Q

What primarily influences a GIA cut grade?

A

The diamond’s proportions

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4
Q

Which factors can lower the cut grade of a diamond?

A
  • Extremely large table facet
  • Very steep crown
  • Very deep pavilion
  • Thick girdle
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5
Q

What is the first step in evaluating a diamond’s proportions?

A

Determine the diamond’s average girdle diameter

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6
Q

How is the average girdle diameter calculated?

A

Add the smallest and largest diameter measurements and divide by two

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7
Q

What does total depth percentage express?

A

The diamond’s table-to-culet depth as a percentage of its average girdle diameter

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8
Q

How is the diameter of a round diamond defined?

A

The distance from one girdle edge to the opposite girdle edge, straight through the center

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9
Q

What is the formula for calculating average girdle diameter?

A

Average Girdle Diameter = (Minimum Girdle Diameter + Maximum Girdle Diameter) ÷ 2

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10
Q

What measurement unit is used for diamonds?

A

Millimeters

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11
Q

True or False: A stone is always perfectly round.

A

False

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12
Q

What should you do to ensure accurate measurements of a diamond’s diameter?

A

Take several diameter measurements

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13
Q

When calculating a diamond’s proportions, to what place should the average girdle diameter result be used?

A

To the thousandths place

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14
Q

How do you calculate the total depth percentage of a diamond?

A

Total Depth Percentage = (Depth ÷ Average Girdle Diameter) × 100

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15
Q

What is the significance of total depth percentage in diamonds?

A

Helps determine why a diamond is underweight or overweight in relation to its diameter

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16
Q

What is the typical total depth percentage for well-proportioned diamonds?

A

Around 60.0 percent

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17
Q

What total depth percentage indicates a diamond is generally underweight?

A

Below 55.0 percent

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18
Q

What characteristics are associated with underweight diamonds?

A
  • Shallow crowns
  • Shallow pavilions
  • Large tables
  • Thin girdles
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19
Q

What total depth percentage indicates a diamond is generally overweight?

A

65.0 percent or more

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20
Q

What characteristics are associated with overweight diamonds?

A
  • Steep crowns
  • Deep pavilions
  • Thick to extremely thick girdles
  • Large tables
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21
Q

Fill in the blank: A diamond with a total depth below 55.0 percent is generally _______.

A

[underweight]

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22
Q

Fill in the blank: A diamond with a total depth of 65.0 percent or more is generally _______.

A

[overweight]

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23
Q

What is the rounding convention for the total depth percentage result?

A

Round to the nearest tenth of a percent

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24
Q

What is a well-proportioned diamond’s total depth percentage compared to underweight and overweight diamonds?

A

60.0 percent is well-proportioned; underweight is below 55.0 percent; overweight is 65.0 percent or more

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25
What does a total depth percentage of 60.0 percent indicate in a diamond?
Good proportions ## Footnote However, it does not guarantee good quality due to potential negatives like a shallow crown or thick girdle.
26
Why are matched table sizes essential when setting diamonds together in jewelry?
They ensure a noticeable and consistent appearance between large side stones ## Footnote This is particularly important in designs like a three-stone anniversary ring.
27
What is the largest facet on a diamond called?
Table ## Footnote The table acts as a window into the diamond's interior.
28
What does the table size of a diamond indicate?
Table percentage: a percentage of the stone’s average girdle diameter.
29
If a diamond’s average girdle diameter is 10 mm, what is the size of a 50-percent table?
5 mm across
30
What is the typical range of table percentages for round brilliant diamonds?
55 percent to 65 percent
31
How does table size affect a diamond's brightness and fire?
It must be considered in relation to the diamond’s other proportions.
32
What is a key factor in diamond sales across different markets?
Individual customer choice ## Footnote This highlights the importance of understanding market preferences.
33
What effect does a very small table (below 50 percent) have on a diamond?
Negative effect on face-up appearance and cut grade.
34
What effect does a very large table (above 70 percent) have on a diamond?
Negative effect on face-up appearance and cut grade.
35
What is needed to measure a diamond's table accurately?
A table gauge, a loupe or microscope, and a good light source ## Footnote The table gauge is a transparent measuring device divided into millimeters and tenths of a millimeter.
36
What is the purpose of the holder when using a loupe?
To keep the loose stone steady while measuring ## Footnote The holder can be fashioned from soft wood, foam, or corrugated cardboard.
37
How should you prepare the holder for a loose stone?
Make a tiny dent just deep enough for the stone's table to be flush with the holder's surface ## Footnote This ensures accurate measurement by stabilizing the stone.
38
What should you do when using a microscope to measure a diamond?
Close the iris diaphragm until the opening is slightly smaller than the stone's diameter ## Footnote This helps in securely holding the diamond in place.
39
What is the recommended measurement technique for a round brilliant's table?
Measure from corner to opposite corner in four directions ## Footnote A round brilliant's table has eight corners.
40
To what precision should the table measurement be taken?
To the nearest five hundredth of a millimeter ## Footnote This means there should be a 5 or a 0 in the hundredths place.
41
What is the final step after measuring the table in four directions?
Add the four measurements and divide by four to find the average ## Footnote The average is used to calculate the diamond's table percentage.
42
Fill in the blank: To measure a diamond's table, you need a _______.
table gauge
43
True or False: A microscope should be tilted when placing the diamond for measurement.
False ## Footnote Tilting the microscope can cause the diamond to fall out.
44
What is the formula for calculating Average Table Diameter?
(Table Measurement + Table Measurement + Table Measurement + Table Measurement) ÷ 4
45
How do you calculate Table Percentage?
(Average Table Diameter ÷ Average Girdle Diameter) × 100
46
What is the typical range for estimating a diamond's table percentage?
50 to 70 percent
47
Why do people in the trade often estimate a diamond’s table percentage?
It takes less time and requires less equipment than direct measurement
48
What are the three estimation methods for table percentage?
* Flash * Ratio * Bowing
49
True or False: Estimation methods can be used to double-check results.
True
50
Fill in the blank: The result of the table percentage calculation should be rounded to the nearest _______.
whole percentage
51
What is the first step in calculating the average table diameter?
Add the table measurements together
52
What method might merchandisers use to sort diamonds quickly?
The flash method ## Footnote The flash method is a simple way to estimate a diamond's table percentage.
53
What does the flash method help estimate?
A diamond's table percentage ## Footnote It provides a quick estimation suitable for immediate sorting needs.
54
What is the first step in using the flash method?
Look at the diamond in the face-up position and rock it back and forth under an overhead light source ## Footnote This helps to observe the flash of light reflecting off the table.
55
What does the size of the flash indicate in the flash method?
The estimated table percentage ## Footnote The perception of the flash size is used to gauge the table size.
56
If the flash is small, what is the estimated table size?
Less than 60 percent ## Footnote This indicates a smaller table size relative to the diamond's face-up view.
57
What does a medium-sized flash indicate about the table size?
Somewhere between 60 and 64 percent ## Footnote This range represents a moderate table size.
58
What is indicated by a large flash in the flash method?
The table size is probably 65 percent or greater ## Footnote A large flash suggests a larger table relative to the diamond's face-up view.
59
What is necessary for the flash method to work accurately?
Practice looking at many different table sizes under reflected light ## Footnote Familiarity with various sizes improves estimation accuracy.
60
What table size is indicated by this flash?
53-59%
61
What table size is indicated by this flash?
60-64%
62
What table size is indicated by this flash?
65%+^
63
What is the first step in using the ratio method?
Look at the stone in the face-up position under magnification with darkfield lighting.
64
What should be centered under the table when using the ratio method?
The culet.
65
What should you do if the stone has an off-center table or culet? ## Footnote ratio method
Tip the stone slightly until the culet appears in the center of the table.
66
What is the reference value in the ratio method? ## Footnote ratio method
1.
67
How do you visualize the reference line in the ratio method? ## Footnote ratio method
A line that runs from the edge of the girdle through the point of a star facet and the edge of the table, ending in the center of the table.
68
What does the inner section of the reference line run from? ## Footnote ratio method
Table edge to culet.
69
What is the ratio when both the outer and inner sections are the same length? ## Footnote ratio method
1:1.
70
What happens to the inner distance as the table gets larger? ## Footnote ratio method
It increases.
71
What is the ratio if the inner distance is twice as long as the outer distance? ## Footnote ratio method
1:2.
72
What approximate table percentage is associated with a 1:1 ratio? ## Footnote ratio method
54%.
73
What approximate table percentage is associated with a 1:1¼ ratio? ## Footnote ratio method
60%.
74
What approximate table percentage is associated with a 1:1½ ratio? ## Footnote ratio method
65%.
75
What approximate table percentage is associated with a 1:1¾ ratio? ## Footnote ratio method
69%.
76
What approximate table percentage is associated with a 1:2 ratio? ## Footnote ratio method
72%.
77
What should you do for ratios between those given? ## Footnote ratio method
Interpolate to estimate a number that falls between two values.
78
What should you do after interpolating a table percentage? ## Footnote ratio method
Repeat the process in at least one more location and then average your results.
79
What adjustment should be made if the table’s eight sides are not approximately the same length? ## Footnote ratio method
Add 1 percent for slight variation and 2 percent for noticeable variation.
80
What method is used to estimate table size? ## Footnote Bowing method
Bowing method ## Footnote The bowing method involves analyzing the lines formed by star facets on the stone's table.
81
What should you look for under magnification when estimating table size? ## Footnote Bowing method
The stone face-up with overhead lighting ## Footnote Proper lighting and magnification are crucial for accurate assessment.
82
How many lines are evaluated to form the outline of a box? ## Footnote Bowing method
Four lines ## Footnote Each line connects points of adjacent star facets.
83
If a line bows in noticeably, what is the table percentage? ## Footnote Bowing method
53 percent ## Footnote This indicates a significant inward curve.
84
What table percentage corresponds to a line that bows in slightly? ## Footnote Bowing method
58 percent ## Footnote This indicates a minor inward curve.
85
What is the table percentage if the lines are straight? ## Footnote Bowing method
60 percent ## Footnote Straight lines indicate no bowing.
86
If a line bows out slightly, what is the corresponding table percentage? ## Footnote Bowing method
63 percent ## Footnote This indicates a minor outward curve.
87
What table percentage is assigned if the line bows out noticeably? ## Footnote Bowing method
67 percent ## Footnote A noticeable outward curve suggests a higher percentage.
88
What should be done for values in between the specified percentages? ## Footnote Bowing method
Interpolate a percentage ## Footnote This allows for more precise measurements.
89
How do you find the overall table percentage after evaluating all lines? ## Footnote Bowing method
Average the percentages of all eight lines ## Footnote Averaging provides a final estimate of the table size.
90
What is the purpose of the bowing method?
To judge if the lines are straight or how much they bow in or out ## Footnote This method involves examining all eight lines to estimate the overall table size.
91
What should you examine to arrive at an overall table size estimate? ## Footnote Bowing method
All eight lines and the two squares formed by the sides of the table and star facets ## Footnote This involves checking for any deviations in the lines.
92
What adjustment must be made if the star facets reach more than or less than halfway to the girdle? ## Footnote Bowing method
Adjust your estimate slightly ## Footnote This is necessary to account for the length of the star facets.
93
How far do star facets normally extend? ## Footnote Bowing method
About half the distance between the girdle and the edge of the table ## Footnote This is a standard measurement used in the bowing method.
94
What effect do longer star facets have on the appearance of the lines? ## Footnote Bowing method
They make the line appear to bow in more ## Footnote This optical effect needs to be compensated for in estimates.
95
What effect do shorter star facets have on the appearance of the lines? ## Footnote Bowing method
They make the line appear to bow out more ## Footnote Understanding this helps in adjusting the table size estimate.
96
Fill in the blank: Adjust the table size estimate to compensate for the _______. ## Footnote Bowing method
[optical effect] ## Footnote This adjustment is critical for accurate assessment.
97
Bowing method, what you do when see this kind of star facets?
Substract 6%
98
Bowing method, what you do when see this kind of star facets?
Nothing
99
Bowing method, what you do when see this kind of star facets?
Add 6%
100
What effect do longer star facets have on the appearance of a reference line?
They make the line appear to bow in more, making the table look smaller than it actually is.
101
What effect do shorter star facets have on the appearance of a reference line?
They make the line appear to bow out more, causing the table to look larger.
102
If star facets reach two-thirds of the way to the girdle, how much should you adjust your estimate?
Add 6 percent to your estimate.
103
If star facets reach only a third of the way to the girdle, how should you adjust your estimate?
Subtract 6 percent from your estimate.
104
What should you do if star facets reach halfway to the girdle?
Make no adjustment.
105
What adjustment should be made if the table is not a regular octagon with slight variation?
Add 1 percent.
106
What adjustment should be made if the table is not a regular octagon with noticeable variation?
Add 2 percent.
107
Fill in the blank: Shorter star facets make the line appear to bow out more, so the table looks _______.
larger.
108
Fill in the blank: If the star facets reach two-thirds of the way to the girdle, you should _______ your estimate.
add 6 percent to.
109
True or False: If the star facets reach halfway to the girdle, you need to adjust your estimate.
False.
110
What are star facets in a round brilliant diamond? ## Footnote Star Length Percentage
Star facets are facets that start at the table edge and extend toward the girdle.
111
How do star facets affect a diamond? ## Footnote Star Length Percentage
They can affect both brightness and fire.
112
What is the star length percentage? ## Footnote Star Length Percentage
The star length percentage estimates the lengths of a diamond’s star facets as a percentage of the total distance between girdle edge and table edge.
113
What is the recommended position to hold a diamond for measuring star facets? ## Footnote Star Length Percentage
Hold the diamond girdle to girdle in the face-up position.
114
What tool should be used for measuring star facets? ## Footnote Star Length Percentage
Use tweezers rather than a stoneholder.
115
What magnification should be used to examine the diamond? ## Footnote Star Length Percentage
Examine the stone under 10x magnification.
116
What is the first step in estimating star facet lengths? ## Footnote Star Length Percentage
Examine all eight star facets clockwise around the gem.
117
If the distance between the edge of the table facet and the girdle is considered 100 percent, what percentage corresponds to one-third of the way? ## Footnote Star Length Percentage
Approximately 35 percent.
118
What is the star length percentage for halfway to the girdle? ## Footnote Star Length Percentage
50 percent.
119
What does two-thirds of the way to the girdle correspond to in star length percentage? ## Footnote Star Length Percentage
Approximately 65 percent.
120
What is the star length percentage for three-quarters of the way toward the girdle edge? ## Footnote Star Length Percentage
75 percent.
121
What should you do after estimating star lengths for all eight facets? ## Footnote Star Length Percentage
Average them and round to the nearest 5 percent.
122
What is the typical range for star length percentages? ## Footnote Star Length Percentage
Typically range from 50 to 55 percent.
123
What are long stars in terms of star length percentage? ## Footnote Star Length Percentage
Stars with percentages from 65 to 70 percent.
124
What is considered rare in star length percentages? ## Footnote Star Length Percentage
Very short stars below 35 percent.
125
What does it indicate if a diamond’s star length percentages differ noticeably? ## Footnote Star Length Percentage
The stone is not symmetrical.
126
What are star length variations considered in the context of diamonds? ## Footnote Star Length Percentage
Part of the symmetry assessment.
127
Estimate Star Length Percentage
35%
128
Estimate Star Length Percentage
40%
129
Estimate Star Length Percentage
45%
130
Estimate Star Length Percentage
50%
131
Estimate Star Length Percentage
55%
132
Estimate Star Length Percentage
60%
133
Estimate Star Length Percentage
65%
134
Estimate Star Length Percentage
70%
135
What are the two crown proportions that can affect a diamond’s appearance?
Crown angle and crown height percentage ## Footnote Crown angle is the angle formed by the bezel facets and the girdle plane, while crown height percentage is the distance from the girdle plane to the table, expressed as a percentage of average girdle diameter.
136
Which is considered more important in the trade, crown angle or crown height?
Crown angle ## Footnote Crown angles from about 25 to about 35 degrees produce attractive, bright, and fiery diamonds if other proportions are compatible.
137
What crown angle range generally produces attractive diamonds?
About 25 to about 35 degrees ## Footnote This range is effective if other proportions are compatible.
138
How can you estimate a round brilliant diamond’s crown angle?
In the profile or face-up position ## Footnote It is recommended to try both methods and compare results for accuracy.
139
What is the advantage of the profile method for estimating crown angle?
The estimate is based on a view of the actual crown angle ## Footnote This contrasts with methods based solely on reflection patterns.
140
What is a challenge of the face-up method for estimating crown angle?
It might be a little challenging at first ## Footnote However, it is useful if a stone is mounted, as it may be the only method available.
141
What is a benefit of using the face-up method for estimating proportions?
It allows you to keep the diamond in the same position for assessing most of its proportions ## Footnote Many other proportion estimation techniques are done in the face-up position.
142
Fill in the blank: Crown angle is the angle formed by the _______ and the girdle plane.
bezel facets
143
Fill in the blank: Crown height percentage is expressed as a percentage of the average _______.
girdle diameter
144
What is the first step in estimating the crown angle using the profile method?
Hold the diamond table-to-culet and look at it under magnification with overhead or dark field light.
145
Which facets should be examined to estimate the crown angle?
Bezel facets.
146
What should not be confused with bezel facets when estimating the crown angle?
Star and upper half facets.
147
What is the appearance of the bezel facet in profile?
It has a flat plane.
148
What is the significance of a right angle in degrees?
90 degrees.
149
What is half of a right angle in degrees?
45 degrees.
150
What is one-third of a right angle in degrees?
30 degrees.
151
How sensitive is the human eye to differences in angles?
Quite sensitive.
152
What magnification should be used when judging the crown angle with the profile method?
10x magnification.
153
When using tweezers to hold the diamond, what position should it be in?
Table-to-culet.
154
Fill in the blank: To estimate the crown angle, recall that half of a right angle is _______ degrees.
[45 degrees]
155
Fill in the blank: To estimate the crown angle, recall that one-third of a right angle is _______ degrees.
[30 degrees]
156
Judge a diamond’s crown angle
40º Steep
157
Judge a diamond’s crown angle
38º Moderately Steep
158
Judge a diamond’s crown angle
36º Slightly Steep
159
Judge a diamond’s crown angle
34.5º
160
Judge a diamond’s crown angle
32º Slightly Shallow
161
Judge a diamond’s crown angle
30º Moderately Shallow
162
Judge a diamond’s crown angle
28º Shallow
163
What is the face-up method used for? ## Footnote crown angle
To estimate a round brilliant’s crown angle ## Footnote This method involves examining the diamond under magnification with darkfield lighting.
164
How should the diamond be held when using the face-up method? ## Footnote crown angle
Girdle-to-girdle with tweezers
165
When estimating the crown angle, what two parts should the pavilion main be mentally divided into? ## Footnote crown angle
* From the culet to the corner where the table meets the bezel facet * Through the bezel facet to the girdle edge
166
What does a greater difference between the two widths of the pavilion main indicate? ## Footnote crown angle
A steeper crown angle
167
What appearance does a 25-degree crown angle have?
The width of the pavilion main appears the same in both sections
168
How does a 30-degree crown angle affect the pavilion main's appearance?
The pavilion main appears slightly wider at the bezel facet
169
What visual change occurs with a 34.5-degree crown angle?
The pavilion main looks nearly twice as wide at the bezel facet
170
What does a 39-degree crown angle reveal about the pavilion main?
The pavilion main looks more than twice as wide at the bezel facet
171
What can be seen with a crown angle of 40 degrees and beyond?
The entire image of the pavilion main and sometimes even the culet
172
What should be done after looking at all eight pavilion mains? ## Footnote crown angle
Mentally average the results to arrive at a final figure
173
What characteristics do stones cut from shallow rough often exhibit? ## Footnote crown angle
* Shallow crown angles * Large tables * Thin girdles * Shallow pavilions
174
What do most modern round brilliant diamonds with steep crown angles have?
* A large table, creating a flat top * A high crown
175
What does a high crown add to a diamond? ## Footnote crown angle
Weight but contributes nothing to girdle diameter
176
What effect does extra weight of the crown have on the diamond's appearance?
It doesn’t necessarily make the stone look larger
177
What can uneven crown angles lead to?
An off-center table, causing an unbalanced appearance
178
Why are crown angle variations important?
They are considered when determining a diamond’s symmetry rating
179
What is considered a deep crown height percentage?
A crown height percentage of 18.5 percent or greater
180
What does a thick crown help to conserve?
Weight
181
What characteristics indicate that a diamond probably weighs more than its face-up diameter indicates?
Deep crown, slightly thick to extremely thick girdle, normal to slightly steep pavilion
182
To determine the crown height percentage, which two measurements are required?
Table percentage and crown angle
183
What chart is referred to for determining the crown height percentage?
Crown Height Percentage Chart
184
What is created during the final brillianteering stage of a diamond?
A diamond's girdle ## Footnote The girdle can be bruted, polished, or faceted.
185
What is the typical thickness of a round brilliant’s girdle?
Usually less than half a millimeter
186
What are the functions of a diamond's girdle?
* Prevent damage * Provide an edge for setting the stone into jewelry
187
Why should the girdle be thick enough?
To prevent chipping
188
What does extra thickness in a girdle contribute to a diamond?
Adds weight, but contributes nothing to appearance
189
What can a thick, unpolished girdle cause?
An unattractive gray reflection in the stone
190
What risks are associated with a girdle that is too thin?
Durability risks
191
What issues can arise from both a thick and thin girdle?
Setting problems
192
What does a thick girdle do to the cost of a diamond?
Increases the cost without enhancing attractiveness
193
How many narrow 'valley' and broader 'hill' positions are on a standard round brilliant girdle?
* 16 narrow 'valley' positions * 16 broader 'hill' positions
194
Where should girdle thickness be assessed?
At the valley positions, where the upper and lower half facets are closest to each other
195
What is the method for estimating girdle thickness?
Examine the entire circumference of the stone, in profile, under 10x magnification with darkfield lighting.
196
What should you consider when assessing girdle thickness?
Clarity characteristics that might be present.
197
How should a natural nearly perpendicular to the table plane be treated in girdle thickness assessment?
Consider it part of the girdle and include it in the assessment.
198
What should you do if the natural is tilted?
Exclude it from the girdle thickness evaluation.
199
What can narrow the girdle during thickness assessment?
An extra facet, natural, chip, cavity, or indented natural located on the crown or pavilion at the girdle edge.
200
If a chip, cavity, or indented natural extends from the girdle onto the crown and pavilion, how should it be treated?
Don’t consider its effect on girdle thickness.
201
What are the descriptive terms for minimum and maximum girdle thicknesses? List them.
* Extremely thin (ETN) * Very thin (VTN) * Thin (THN) * Medium (MED) * Slightly thick (STK) * Thick (THK) * Very thick (VTK) * Extremely thick (ETK)
202
What does Extremely thin (ETN) indicate in terms of girdle thickness?
A sharp edge at 10x, called a knife-edge.
203
What does Very thin (VTN) indicate in terms of girdle thickness?
A very thin line at 10x.
204
What does Medium (MED) indicate in terms of girdle thickness?
A distinct line at 10x.
205
What is the usual reporting format for girdle thickness?
In a thin-to-thick range, for example, Very Thin to Medium.
206
When is a single description sufficient for girdle thickness?
When both the minimum and maximum thicknesses are in the same category.
207
What does Thick (THK) indicate in terms of girdle thickness?
Very obvious at 10x.
208
What are the three types of diamond girdles?
Bruted, faceted, polished ## Footnote The girdle can also have minute parallel grooves cut by a laser.
209
What is a characteristic of a laser-cut diamond girdle?
It has minute parallel grooves ## Footnote This is a distinct feature compared to other girdle types.
210
True or False: All diamond girdles are polished.
False ## Footnote Diamond girdles can be bruted, faceted, or polished.
211
estimate girdle thickness
Extremely Thin (ETN): Knife-Edge
212
estimate girdle thickness
Very Thin (VTN): A Very Thin Line at 10x
213
estimate girdle thickness
Thin (THN): A Thin Line at 10x
214
estimate girdle thickness
Medium (MED): Distinct at 10x
215
estimate girdle thickness
Slightly Thick (STK): Obvious at 10x
216
estimate girdle thickness
Thick (THK): Very Obvious at 10x
217
estimate girdle thickness
Very Thick (VTK): Distracting at 10x
218
estimate girdle thickness
Extremely Thick (ETK): Very Distracting at 10x
219
What should be examined to estimate girdle thickness?
The narrowest sections, where the upper and lower half facets meet ## Footnote This is crucial for accurate measurement.
220
How is girdle thickness described when it is very obvious at 10x?
Thick (THK) ## Footnote This classification helps in assessing the girdle's appearance.
221
What is the description for a girdle thickness that is distracting at 10x?
Very thick (VTK) ## Footnote Such thickness can significantly impact the overall appearance of the gem.
222
What does the term 'Medium (MED)' indicate in girdle thickness?
A distinct line at 10x ## Footnote This indicates a moderate level of thickness.
223
What is the classification for girdle thickness that appears as a thin line at 10x?
Thin (THN) ## Footnote This is the least thickness classification.
224
What term is used for girdle thickness that is very distracting at 10x?
Extremely thick (ETK) ## Footnote This level of thickness can detract from the gem's overall visual appeal.
225
What is the significance of reporting girdle thickness in a range?
Girdle thickness is reported in a thin-to-thick range, e.g., Very Thin to Medium ## Footnote This provides a clearer understanding of the thickness variation.
226
Fill in the blank: A girdle thickness that is obvious at 10x is classified as _______.
Slightly thick (STK) ## Footnote This term indicates a noticeable thickness.
227
What does a single description of girdle thickness indicate?
Both the minimum and maximum thicknesses are in the same category ## Footnote This simplifies the reporting of thickness.
228
What is the effect of a normal girdle on a diamond's thickness?
The hill positions are all about the same thickness, resulting in fairly even scalloping all around the diamond.
229
How can a cutter retain weight in a round brilliant diamond?
By increasing girdle thickness all the way around the diamond or only in selected locations.
230
What are the weight-saving techniques used during fashioning?
Painting and digging out.
231
What is the result of severe painting and digging out techniques?
Significant thickness differences between adjacent hill positions and uneven scalloping around the diamond’s girdle.
232
What is the process of painting in diamond cutting?
A process of very light polishing that allows the cutter to gently polish away less thickness at selected locations around the girdle.
233
When a diamond is painted, how are the upper or lower half facets positioned?
Tilted toward the bezel facets or pavilion mains.
234
In a painted diamond, where are the hill positions thicker?
Where the upper half facet junctions meet the lower half facet junctions.
235
What occurs with the digging out technique in diamond cutting?
The cutter tilts the upper or lower half facets away from the bezel or pavilion facets and toward each other.
236
In a dug-out diamond, where are the hill positions thinner?
Where the upper half facet junctions meet the lower half facet junctions.
237
Why do cutters often use the digging out technique?
To remove naturals or blemishes at the girdle.
238
What is the initial girdle thickness left by the cutter during the cutting process?
A thicker girdle around the entire diamond.
239
What happens to clarity characteristics during the finishing process?
They are removed or 'dug out', leaving some of the additional girdle thickness.
240
Can digging out be done at multiple locations on the girdle?
Yes, it might be done at just one place or symmetrically at a number of places.
241
What does painting refer to in gem cutting?
Tilting upper or lower half facets toward the bezel or main
242
What effect does more painting on the crown have?
The fainter the bezel facet junctions
243
What happens when there is more painting on the pavilion?
The fainter the main facet junctions
244
What is the result of more digging out on the crown?
The fainter the upper half facet junctions
245
What is the consequence of more digging out on the pavilion?
The fainter the lower half facet junctions
246
Name the method
Painting on the Crown
247
Name the method
Painting on the Pavilion
248
Name the method
Crown with Digging Out
249
Name the method
Pavilion with Digging Out
250
251
What can change the face-up appearance of a diamond?
Strong painting or digging out
252
What effect does significant painting have on a diamond?
Causes large areas of the diamond to flash all at once, changing the balance of the diamond’s face-up pattern
253
What might digging out produce in a diamond?
Dark upper half facets, making the stone look dark face-up and smaller
254
How does severe digging out affect the appearance of a diamond?
Makes some crown facet junctions appear less sharp and adjacent upper half facets look like a single large facet
255
What is a consequence of severe digging out on a diamond's pattern?
Significantly alters the diamond’s pattern by causing larger areas to flash at the same time
256
Describe effect of painting/digging
Diamonds with significant painting only on the crown are generally not as bright as unpainted diamonds. You might also see a pattern of dark radiating mains.
257
Describe effect of painting/digging
Severe digging out on the crown tends to darken upper half facets and make them appear to “blend” together. It also alte
258
Describe effect of painting/digging
Diamonds with painting on both crown and pavilion can display more extreme effects, with broad bright and dark areas that radiate out from their centers.
259
Describe effect of painting/digging
Painting only on the pavilion saves more weight than painting only on the crown. Severe painting creates a strong visual impact with broad, radiating bright and dark areas.
260
Describe effect of painting/digging
Digging out only on the pavilion saves more weight than digging out on the crown. It might produce an interrupted pattern and an overall gray appearance.
261
Describe effect of painting/digging
Digging out on both crown and pavilion produces more extreme effects. The stone’s center often appears dark, with a bright band blending into a dark band at the table edge.
262
What are the five cut grade ranges established by GIA researchers?
Excellent, Very Good, Good, Fair, Poor
263
What is the purpose of the GIA Cut Grading System?
To predictively plan diamond cuts for achieving top grades
264
How do GIA researchers evaluate a diamond’s cut?
Using a combination of visual observation and computer models of light behavior in diamonds
265
Fill in the blank: A diamond with a total depth percentage of 57 percent would never qualify as _______.
Excellent
266
What does the GIA Cut Grading System allow manufacturers to do?
Plan diamond cuts to achieve top grades
267
What is required for a diamond to receive the highest possible cut grade?
Specific proportions based on the GIA grading tables
268
True or False: The GIA Cut Grading System allows for easy and consistent evaluation of a diamond’s cut.
True

Gemmology (42 decks)

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