Chapter 13 Flashcards
What is the process of transforming diamond rough into a finished gem called?
A remarkable process
Who is responsible for turning rough crystals into finished diamonds?
Skilled cutters
What are the key factors that affect a diamond’s appearance and value?
Basic diamond proportions and their variations
What part of a round brilliant diamond affects how light enters and exits the stone?
The top portion, including its table and crown
What governs the initial path light takes once it’s inside a diamond?
The diamond’s lower half, known as the pavilion
What can make the difference between a lifeless diamond and one that dances with light and color?
The diamond’s surface appearance and cut precision
Why is the pavilion important in a diamond’s appearance?
It determines the path light takes inside the diamond
What do the pavilion facets do with the light that enters from above?
Reflect it back toward the crown
What unique ability of diamonds does the pavilion take advantage of?
Breaking up light into its spectral colors and creating fire
Fill in the blank: The diamond’s surface appearance and cut precision—its _______—can affect its visual appeal.
finish
What are the keys to a well-proportioned pavilion?
Careful planning and skilled cutting
This emphasizes the importance of both design and construction techniques in achieving structural balance.
What is the primary method for estimating a diamond’s pavilion depth percentage?
Identifying and interpreting the reflections seen through a diamond’s table.
Estimation is usually accurate enough for grading and appraising.
What does the reflection of the pavilion facets look like when viewing a round brilliant diamond face-up?
An octagonal or circular image centered around the culet.
The reflection can be white, gray, silver, or black.
How can you find the table reflection of a diamond?
Look at the diamond face-up under magnification with darkfield lighting and rock it back and forth.
Look for the dark triangular reflections of the star facets.
What do the pairs of dark triangular reflections of the star facets resemble?
Tiny black bow-ties.
They connect together to provide an outline of the table reflection.
What can affect the reflection pattern of the star facets in a diamond?
Minor cutting variations, like misalignment between the crown and pavilion or a slightly tilted facet.
These variations can distort the reflections.
What is another method to locate the table reflection of a diamond?
Using a pointer to position at one corner of the table and observing the pointer’s reflection in the pavilion.
The pointer reflection ends at the edge of the table reflection.
How does the pavilion depth percentage affect the reflected image size in a diamond?
The smaller the reflection, the lower the pavilion depth percentage.
This is determined by how much space the reflection occupies between the culet and the table corner.
What pavilion depth percentage is indicated by a table reflection that reaches about one-third of the distance from the culet to the corner of the table?
About 43 percent.
At this percentage, the table reflection is fairly small.
What does a table reflection reaching about halfway from the culet to the table corner indicate?
A pavilion depth percentage of 44.5 percent.
How does culet size affect pavilion depth?
A larger culet results in a shallower pavilion than one with a smaller culet at the same pavilion angle.
Evaluate pavilion depth precentage.
41%
Evaluate pavilion depth precentage.
42%
Evaluate pavilion depth precentage.
43%
Evaluate pavilion depth precentage.
44.5%
Evaluate pavilion depth precentage.
45.5%
Evaluate pavilion depth precentage.
47%
Evaluate pavilion depth precentage.
49%
Evaluate pavilion depth precentage.
> 50%
Name the effect and explain reason
This diamond’s deep pavilion causes excessive light leakage, making the stone appear extremely dark in the center. This is called a nailhead.
Name the effect and explain reason
This diamond’s pavilion is so shallow that you can see the girdle’s reflection just inside the table facet. This effect is called a fisheye.
What happens to diamonds with pavilions deeper than 48 percent?
They usually look dark in the center
This effect is due to the pavilion depth affecting light reflection.
What occurs at a pavilion depth of 50 percent or more?
The darkness covers the entire table and extends into the star facets
This results in the diamond looking very dark.
What is the term used for diamonds that appear very dark due to deep pavilions?
Nailhead
What do pavilion depth percentages under 41 percent result in?
Small, fragmented table reflections that are difficult to distinguish
The girdle reflection begins to become visible at this depth.
What effect is observed in round brilliants with pavilions shallower than 38 percent?
The girdle reflection forms an unattractive gray ring visible just inside the table facet
This effect is known as a fisheye.
What is a fisheye?
An effect that gives the stone a dull, flat look due to a gray ring from the girdle reflection
It can occur in stones with a large table and a pavilion depth up to about 40 percent.
How does culet size affect pavilion depth estimation?
As the culet gets larger, pavilion depth gets slightly shallower
Adjustments to estimates are needed when a culet is present.
What is the relationship between pavilion depth percentage and pavilion angle?
Generally, the greater the pavilion depth percentage, the steeper the pavilion angle.
What effect does an extremely shallow pavilion angle (less than 37.4 degrees) have on a diamond’s appearance?
It has a very negative effect, producing dark areas under the diamond’s table.
What effect does an extremely steep pavilion angle (greater than 44.0 degrees) have on a diamond’s appearance?
It has a very negative effect, producing dark areas under the diamond’s table.
What unattractive reflection effects can shallow pavilion angles combined with large tables and shallow crown angles produce?
They might produce unattractive reflection effects like fisheyes.
What happens when the pavilion angle is increased too much?
It causes light leakage and makes the center of the stone darker.
How can variations in pavilion angle affect a diamond’s appearance?
Slight imbalances might cause some returning light to hit the crown outside the critical angle, resulting in uneven brightness and scintillation.
What is the result of uneven brightness and scintillation in diamonds?
It makes the reflection pattern more difficult to see.
Who can easily note the differences in appearance between diamonds with shallow and deep pavilions?
Experienced diamond professionals.
Fill in the blank: Increasing the pavilion angle too much causes _______.
light leakage
True or False: A pavilion angle that is very shallow can create fisheyes in the diamond’s appearance.
True
What does a steep pavilion angle produce under the diamond’s table?
Dark areas
What are the three final pieces of information needed to determine a diamond’s cut grade?
Girdle thickness percentage, lower half length percentage, culet size
These factors are essential for assessing the overall quality of a diamond’s cut.
How is girdle thickness percentage defined?
Thickness of the diamond’s girdle expressed as a percentage of its average girdle diameter
This measurement helps in understanding the diamond’s proportions.
What does lower half length percentage represent?
Length of the lower half facets expressed as a percentage of the total distance between the girdle and the culet
This percentage is crucial for evaluating the lower half of the diamond.
What is culet size?
Size of the facet at the bottom of the diamond where the pavilion mains meet
The culet is important for light performance and overall appearance.
What is the relationship between pavilion depth percentage and girdle thickness percentage?
Pavilion depth percentage is used to determine girdle thickness percentage
This calculation is essential for accurate grading.
Where is girdle thickness assessed?
At the girdle’s thickest areas—the hills—where the bezel facets meet the pavilion main facets
This contrasts with using the valleys for assessment in previous assignments.
What areas of the girdle were used to assess girdle thickness in Assignment 12?
The girdle’s narrowest areas—the valleys
This method differs from the current assessment method focusing on the thickest areas.
How do you calculate girdle thickness percentage?
Subtract crown height percentage and pavilion depth percentage from total depth percentage and round to the nearest 0.5 percent
This formula provides a precise measure of girdle thickness.
Fill in the blank: Girdle thickness percentage is assessed at the _______ of the diamond.
girdle’s thickest areas
This is where the bezel facets meet the pavilion main facets.
True or False: Girdle thickness percentage is calculated using only the crown height percentage.
False
It requires both crown height percentage and pavilion depth percentage in the calculation.
What can limit a diamond’s possible cut grade?
Girdle thickness percentage
What girdle thickness percentage indicates a lower cut grade?
Greater than 10.0 percent
If a diamond has a girdle thickness percentage of 11.5, what is its cut grade?
Poor
Fill in the blank: A diamond with a girdle thickness percentage greater than _____ will belong in one of the lower cut grades.
10.0 percent
True or False: A diamond with a girdle thickness percentage of 11.5 can have a cut grade higher than Poor.
False
What is the starting point for lower half facets in a diamond?
The girdle
Where do lower half facets extend toward in a round brilliant cut diamond?
The culet
What percentage expresses lower half facet length?
Percentage of the girdle-to-culet distance
How should the diamond be positioned to estimate lower half facet length?
Girdle-to-girdle in the face-up position
Why should a stoneholder not be used during the estimation?
It might cover some of the girdle edge and make the estimate less accurate
What magnification is used to examine lower half facets?
Under 10x magnification
How many pairs of lower half facets are examined?
Eight pairs
What is considered 100 percent in the context of lower half facets?
The distance between the culet and the girdle
If a lower half facet reaches halfway to the culet, what is its length percentage?
50 percent
If a lower half facet reaches three-quarters of the way to the culet, what is its length percentage?
75 percent
If a lower half facet reaches two-thirds of the way to the culet, what is its approximate length percentage?
About 65 percent
What should be done after estimating all lower half facets?
Average the results and round to the nearest 5 percent
What does it indicate if a diamond’s lower half length percentages differ noticeably?
The stone is not symmetrical
What might be off-center if the lower half lengths are not symmetrical?
The culet
What might appear to be different sizes or shapes if the lower half facets differ noticeably?
The pavilion mains
Estimate Lower Half Facet Length Percentage
Estimate Lower Half Facet Length Percentage
Estimate Lower Half Facet Length Percentage
Estimate Lower Half Facet Length Percentage
Estimate Lower Half Facet Length Percentage
Estimate Lower Half Facet Length Percentage
Estimate Lower Half Facet Length Percentage
Estimate Lower Half Facet Length Percentage
What is the culet of a diamond?
The bottom facet of a diamond, located where the pavilion mains meet.
What is the purpose of the culet in a diamond?
To prevent abrasion and chipping on loose diamonds.
Do all diamonds have culets?
No, not all diamonds have culets, and many markets prefer diamonds without them.
How can you determine if a diamond has a culet?
Examine the stone face-up at 10x magnification under darkfield lighting.
What does it indicate if the culet area seems to blink under magnification?
That there is a culet.
What happens if the area does not blink when examining for a culet?
There is no culet; if a fuzzy white speck is seen, the stone’s point is abraded.
How does the size of a diamond’s culet affect its cut grade?
The larger the culet, the lower the cut grade.
What should the culet of a well-cut diamond be sized for?
Just large enough to prevent abrasion or chipping before the stone is set.
What happens if the culet is too large?
It will look like an unattractive black spot when viewed through the table.
How can a culet be described if the pavilion comes to a sharp, unabraded point?
As ‘pointed’.
What should the culet’s surface be in relation to the diamond’s table facet?
Parallel.
What should be observed to assess the angle of the culet?
The diamond’s profile view.
What should be reported if the culet is at more than a slight angle to the table facet?
Consider it an extra facet and report culet size as ‘none’.
How is culet size estimated?
By examining the stone face-up under 10x magnification.
What is the classification for a culet that is absent or has an abraded point?
None.
Describe a ‘very small’ culet.
Barely distinguishable at 10x.
Describe a ‘small’ culet.
Difficult to see at 10x.
Describe a ‘medium’ culet.
Distinct at 10x.
Describe a ‘slightly large’ culet.
Obvious at 10x.
Describe a ‘large’ culet.
Very obvious at 10x.
Describe a ‘very large’ culet.
Distracting at 10x.
Describe an ‘extremely large’ culet.
Very distracting at 10x.
How should any clarity characteristics at the culet be included in assessments?
Consider only the remaining portion of the culet facet under culet size.
What happens if a cutter leaves the culet as an unpolished natural surface?
If nearly parallel to the table facet, consider it a culet and assign the appropriate size description.
Does abrasion affect culet size?
No, but it prevents a Flawless clarity grade.
What aspect does abrasion contribute to in diamond assessment?
The diamond’s polish assessment.
What should the presence of a culet do to your estimate of pavilion depth percentage?
Reduce it.
How is total depth percentage calculated using average girdle diameter?
Total Depth Percentage = Crown Height Percentage + Girdle Thickness Percentage + Pavilion Depth Percentage
This formula is used when direct measurement of a diamond is not possible.
What does a total depth percentage greater than about 65 percent indicate?
Often indicates steep crown or pavilion angles or thick girdles
This can affect the diamond’s overall appearance.
What does a total depth percentage less than about 55 percent typically suggest?
Indicates a thin crown, a shallow pavilion, or a thin girdle
These features are often the result of cutting shallow rough.
What range of total depth percentages is considered attractive and marketable by many diamond professionals?
Between 55 percent and 65 percent
This range includes proportions that are typically seen in well-cut diamonds.
True or False: Total depth percentage should be used as an absolute indicator of a diamond’s appearance.
False
Total depth percentage is a guideline, not an absolute measure.
What can total depth percentage be used to estimate?
A diamond’s weight
More details on this estimation can be found in Assignment 15.
What does GIA include in its cut grade for diamonds?
Design and craftsmanship
Design is determined during the fashioning stage, while craftsmanship reflects the finishing details.
What are the key design factors affecting a diamond’s cut grade?
Weight and durability
Excess weight in thick girdles, steep crowns, or deep pavilions can lead to downgrading.
How does GIA’s Cut Grading System assess diamonds with excess weight?
It downgrades diamonds with thick girdles, steep crowns, or deep pavilions
Vulnerable features like thin girdles also result in lower grades.
What does the craftsmanship judgment in GIA’s grading system reflect?
The care taken in the finishing process
Ratings for polish and symmetry are included in this category.
What is the ‘weight ratio’ in GIA’s Cut Grading System?
The diamond’s weight in relation to its diameter compared to a reference diamond
This ratio is assessed against diamonds with similar average girdle diameter and standard proportions.
What is the standard diameter for a 1.00-ct. round brilliant diamond?
About 6.5 mm
A diamond weighing 1.20 cts. with this diameter may be concealing extra weight.
What is the significance of ‘overweight percentage’ in diamonds?
It expresses the difference between suggested weight and actual weight
This percentage can negatively affect the diamond’s cut grade.
What total depth percentage indicates a diamond may have excessive thickness?
More than 65 percent
This suggests that the crown, pavilion, or girdle may be too thick.
What total depth percentage suggests that a diamond part is too shallow?
Less than 56 percent
This indicates a potential issue with the diamond’s proportions.
Fill in the blank: The GIA Cut Grading System includes ratings for _______.
polish and symmetry
True or False: A diamond with a knife-edge girdle will receive a higher GIA cut grade.
False
Extremely thin girdles are considered vulnerable and tend to receive lower grades.
What is the term used to collectively refer to the details of a diamond’s cut?
Finish
Finish includes both polish and symmetry.
What are the two subcategories that make up a diamond’s finish?
- Polish
- Symmetry
Polish refers to the condition of the diamond’s facet surfaces, while symmetry refers to the exactness of shape and placement of facets.
What does polish refer to in terms of a diamond’s finish?
The overall condition of a finished diamond’s facet surfaces
Polish affects the diamond’s ability to reflect light.
What does symmetry refer to in the context of a diamond’s finish?
The exactness of the shape and the placement of its facets
Symmetry is crucial for the aesthetic appeal of the diamond.
How can one summarize finish on a customer’s appraisal or report?
By noting each polish and symmetry feature
This ensures more complete records for future reference.
What magnification level is used to assess polish and symmetry in diamonds?
10x magnification
This level allows for detailed visibility of the diamond’s variations.
What effect does poor polish have on a diamond?
Makes stones look dull and hazy
Even well-proportioned stones can appear unattractive with poor polish.
Why can diamonds take a better polish than any other gem?
Because of its superior hardness
This hardness allows for a finer finish during the polishing process.
What can affect the polish characteristics of a diamond?
- The finishing process
- Blemishes created after cutting
Both factors can result in variations in polish quality.
What magnification is used to evaluate polish on a diamond?
10x
What type of blemishes affect polish?
Blemishes caused by the polishing process or that result from wear
What does Abr stand for in terms of diamond blemishes?
Abrasion
Define abrasion in the context of diamond polish.
A series of minute scratches or pits along a facet junction, giving the edges a white or fuzzy appearance
What is lizard skin (LS) in diamond polishing?
Wavy or bumpy area with a transparent, pitted texture, which results from polishing off-grain near a cleavage plane
What does Nck represent in diamond blemishes?
Nick
Describe a nick (Nck) on a diamond.
A small notch on a facet junction with no readily apparent depth at 10x, usually along the girdle edge or culet
What is a pit (Pit) in the context of diamond polishing?
A small opening that looks like a tiny white dot at 10x
What are Polish lines (PL)?
Fine, parallel grooves and ridges left by the polishing process. Can appear white (Wht) or transparent (TP), heavy or light.
Heavy polish lines leading from a surface feature, such as a cavity, are called drag lines.
Define Rough girdle (RG).
Irregular or granular surface of a bruted girdle, consisting of pits and nicks.
What is a Scratch (Scr) in diamonds?
A thin, dull, white line across the diamond’s surface, with no apparent depth.
What does Burn (Brn) refer to?
Whitish haze across a facet, caused by excessive heat during polishing or, rarely, by fire from a jeweler’s torch or other source.
A surface burn resulting from excessive heat where the dop touches the diamond is called a dop burn (Dop).
What is a Polish mark?
A surface feature that resembles an extra facet without a distinct or straight facet junction.
What does Laser manufacturing remnant (LMR) mean?
Remains of laser cutting or marking left on the surface of a polished diamond. Affects polish when it’s confined to the surface when viewed at 10x.
Describe the blemish
Nick
Describe the blemish
Nick
Describe the blemish
A polish mark that resembles an extra facet, but have no distinct facet junctions
Describe the blemish
Lizard Skin
Describe the blemish
Lizard Skin
Describe the blemish
Nick
Describe the blemish
Scratch
Describe the blemish
Rough girdle
Describe the blemish
Describe the blemish
Scratch
Describe the blemish
Burn
Describe the blemish
Burn
Describe the blemish
Polish mark
Describe the blemish
Laser manufacturing remnant
What is the precise arrangement of facets in round brilliant diamonds?
58 perfectly shaped facets
Do most diamonds achieve exact symmetry in their cut?
No, most diamonds are not cut to exact symmetry
What are some common symmetry variations found in diamonds?
Facets may be distorted or misaligned, the table or culet might be off-center, or the girdle might look like a warped disk
How do symmetry variations typically affect a diamond’s appearance?
They typically have little effect on appearance, at least to the unaided eye
What aspects should be evaluated to assess a diamond’s symmetry?
Evenness of outline, size, shape, and placement of facets
What magnification should be used to examine a diamond for symmetry?
10x magnification
What is the range of symmetry ratings for diamonds?
Excellent to Poor
What should a round brilliant diamond reveal when viewed face-up?
Eight sections
What does each of the eight sections of a diamond contain?
A complete bezel and pavilion main facet and a pair of upper and lower half facets
What indicates that a diamond is symmetrical when comparing sections?
All eight sections should match
What are most symmetry variations related to?
Proportion-related issues, alignment, and balance of the stone’s table, culet, girdle, and angles
What other factors can cause symmetry variations in diamonds?
Shape, placement, and presence or absence of the facets themselves
What does Out-of-round (OR) refer to in terms of symmetry?
The girdle outline doesn’t look perfectly round and may have a flattened area, referred to as an uneven outline.
What indicates that the table is off-center?
If a bezel on one side of the crown is longer than the bezel on the opposite side.
What is meant by Culet off-center (C/oc)?
The culet is not centered in the pavilion, indicated by seeing more of the pavilion on one side of the culet.
What does table/culet alignment (T/C) describe?
Table and culet are displaced in opposite directions.
What does Girdle thickness variation (GTV) refer to?
Variations in girdle thickness that might occur where crown and pavilion facets meet.
What is crown angle variation (CV)?
Variation in measurements of all eight crown angles on a round brilliant, typically related to T/oc.
What does pavilion angle variation (PV) indicate?
Variation in measurements of all eight pavilion angles on a round brilliant, typically related to C/oc.
What does crown height variation (CHV) measure?
Variation in the diamond’s eight crown height measurements.
What is pavilion depth variation (PDV)?
Variation in the diamond’s eight pavilion depth measurements.
What does star angle variation (SV) refer to?
Unequal star facet angles.
What is star percentage variation (SPV)?
Variation in the diamond’s eight measured star facet length percentages.
What does upper half variation (UHV) indicate?
Unequal upper half facet angles.
What is lower half percentage variation (LPV)?
Variation in the diamond’s eight measured lower half facet length percentages.
What does lower half variation (LHV) describe?
Unequal lower half facet angles.
What does missing facet (MF) mean?
A facet that should be in a given location is absent.
What are Extra facets (EF)?
Facets not required by the cutting style are placed without regard for the diamond’s symmetry, most often near the girdle.
Extra facets can affect the overall appearance and symmetry of the diamond.
Define Natural (N) in diamond cutting.
A portion of the original surface, or skin, of a rough diamond left on a fashioned stone.
This natural surface can influence the diamond’s value and appearance.
What characterizes a Non-octagonal table (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.
What are Misshapen facets (Fac)?
Facets are not properly shaped, or they’re not the same size and shape as others of the same type.
On a brilliant cut, these might be described as misshapen bezel (MB), misshapen star (MS), or misshapen main (MM).
What does Non-pointing (Ptg) refer to?
Facets fail to meet at precise points, or a fully formed facet doesn’t reach its prescribed location.
In a brilliant cut, Ptg might specifically be open main (OM), open bezel (OB), short main (SM), or short bezel (SB).
Define Misalignment (Aln) in diamond cutting.
Crown and pavilion facets not aligned with each other, where points of the bezel and main facets do not align across the girdle.
This misalignment might be referred to as “twist” in the trade.
What are Extra facets (EF)?
Facets not required by the cutting style are placed without regard for the diamond’s symmetry, most often near the girdle.
Extra facets can affect the overall appearance and light performance of a diamond.
What does Natural (N) refer to in diamond cutting?
A portion of the original surface, or skin, of a rough diamond left on a fashioned stone.
Natural inclusions may impact a diamond’s clarity and value.
What is a Non-octagonal table (T/oct)?
The table doesn’t have eight sides of equal length and parallel opposing sides, resulting in misshapen star and bezel facets.
This can lead to uneven light reflection and visual distortion.
Define Misshapen facets (Fac).
Facets are not properly shaped, or they’re not the same size and shape as others of the same type.
Misshapen facets can be specifically categorized as misshapen bezel (MB), misshapen star (MS), or misshapen main (MM).
What does Non-pointing (Ptg) mean?
Facets fail to meet at precise points, or a fully formed facet doesn’t reach its prescribed location.
In a brilliant cut, Non-pointing might be described as open main (OM), open bezel (OB), short main (SM), or short bezel (SB).
What is Misalignment (Aln) in diamond facets?
Crown and pavilion facets not aligned with each other, affecting the alignment of bezel and main facets across the girdle.
Misalignment might be referred to as ‘twist’ in the trade and can lead to a compromised appearance.
True or False: Extra facets are typically located on the pavilion near the girdle.
True
They might also be found in other locations, such as the bezel facets.
Fill in the blank: A diamond with variations in alignment probably also has _______ and pointing.
misshapen facets
These three variations—misalignment, misshapen facets, and pointing—almost always occur together.
What are the ratings used for the polish and symmetry categories on a diamond grading report?
Excellent (Ex), Very Good (VG), Good (G), Fair (F), Poor (P)
These ratings help assess the quality of a diamond’s finish.
What does an Excellent rating in polish or symmetry indicate?
They are ‘superior’
This does not imply perfection; minor imperfections can still allow for an Excellent rating.
What conditions might lead to a Very Good rating for polish and symmetry?
Faint polish lines, insignificant blemishes, slight misalignment
These factors contribute to a Very Good rating.
Under what circumstances might a diamond receive a Good rating?
Transparent polish lines, several small blemishes, slight off-center table or culet, noticeable misalignment
These issues can affect the overall quality but still allow for a Good rating.
What factors could lead to a Fair rating for a diamond’s finish?
Obvious polish lines, burn, noticeable blemishes, wavy girdle, misshapen facets
These characteristics significantly detract from the diamond’s appearance.
What usually characterizes a diamond with a Poor rating?
Polish characteristics that reduce transparency or obvious symmetry variations
A Poor rating indicates serious flaws in the diamond’s finish.
What is the typical rating range for most stones in terms of polish and symmetry?
Good to Very Good
Most diamonds fall within this range, indicating a decent quality.
Why do cutters tend to focus more on large, high-quality stones?
They spend more time on them for better polish and symmetry
Average-quality or average-sized stones receive less attention.
Fill in the blank: A diamond may receive a _______ rating if it has transparent polish lines visible through the pavilion.
Good
What is the significance of a diamond’s proportions?
A difference of a few degrees or percentage points can affect the appearance of a stone.
What are the rarely absolutely perfect aspects of a diamond’s cut?
Polish and symmetry.
After estimating a diamond’s proportions, what is the next step?
Consider them together along with design and craftsmanship factors.
List three factors to consider when evaluating a diamond.
- Carat weight compared to average girdle diameter
- Total depth percentage
- Table percentage
What is one factor that limits a diamond’s potential cut grade?
Each factor considered limits the diamond’s potential cut grade.
True or False: The factor that rates the lowest determines the diamond’s cut grade.
True.
Fill in the blank: The _____ percentage affects the crown of a diamond.
[Crown height]
What does the girdle thickness variation affect?
It is one of the factors that affect a diamond’s appearance.
What is the role of the pavilion angle in diamond evaluation?
It is one of the factors that contribute to a diamond’s overall cut quality.
List four factors that influence a diamond’s appearance.
- Star length percentage
- Crown angle
- Pavilion depth percentage
- Culet size
What are the three aspects of Face-Up Appearance?
Brightness, Scintillation, Fire
What factors are included in the Design aspect?
Weight Ratio, Durability
What are the two components of Craftsmanship?
Polish, Symmetry
What happens when one parameter falls outside the range of a particular cut grade?
The lower level automatically becomes the highest possible cut grade for that diamond.
If a gem’s total depth is 51.2 percent, what is its highest possible cut grade?
Fair or Poor
What girdle thickness limits a diamond’s cut grade to Good, Fair, or Poor?
Very thin (VTN) to very thick (VTK)
What determines the highest possible cut grade of a diamond?
The parameter that is lower than all the others.
If all parameters fit into the Very Good range but polish rates Fair, what is the highest possible cut grade?
Good
Which proportion factors are critical in determining a round brilliant diamond’s brightness?
- Table percentage
- Crown angle
- Pavilion angle
What can cause a cut grade to be lower than expected?
The interaction of two or more factors that negatively affects the grade.
How do stones with table percentages or angles toward the extremes of a cut grade range tend to perform?
They tend to receive one or two grades lower.
What might limit a diamond’s grade to Very Good despite having Excellent parameters?
A visual estimate of its cut.
Why is it important to emphasize the way a diamond looks over its numerical parameters?
Interactions of unfavorable angles might create unattractive features.
What can affect the final cut grade of a diamond according to GIA laboratory results?
Slight differences in measurements due to specialized equipment.
What tools are the procedures in this course designed to be practical for?
The tools most people have available.
How are brightness and fire evaluated in diamonds?
Using computer-modeled calculations refined by human observations.
What is evaluated using a combination of proportion ranges and specific calculations?
Pattern-related aspects of scintillation.
What was the grading scale for each component validated through?
Human observations.
Fill in the blank: The interaction of two unfavorable angles might give a diamond a _______.
[dark pattern or other unattractive feature]
True or False: The lab’s results can vary slightly from personal assessments due to high-definition optical measuring devices.
True
