Ass #13 - Grading Proportions Quiz

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Questions and Answers

What does the term 'star angle variation' refer to in diamond craftsmanship?

Variation in the diamond’s color intensity

Unequal star facet angles (correct)

Inconsistency in the polishing process

Differences in carat weight among diamonds

Which type of variation specifically measures the length percentages of the diamond’s lower half facets?

Lower half percentage variation (LPV) (correct)

Lower half variation (LHV)

Star percentage variation (SPV)

Upper half variation (UHV)

What is indicated by a diamond being rated as 'Excellent' for both polish and symmetry?

The diamond has significant visible flaws

The diamond has minor imperfections that are difficult to find (correct)

The diamond is guaranteed to have perfect angles

The diamond is flawless without any imperfections

Which term describes a facet that should be present but is missing from a diamond?

Missing facet (MF) Signup and view all the answers

What does the term 'non-pointing' refer to in diamond facet alignment?

Facets not reaching their designated locations Signup and view all the answers

What does 'lower half variation (LHV)' specifically measure in a diamond?

Unequal angles of the lower half facets Signup and view all the answers

Which of the following describes facets that are not properly formed or are uneven?

Misshapen facets (Fac) Signup and view all the answers

What does a 'non-octagonal table' imply about a diamond's cut?

The table shape is irregular and affects facet alignment Signup and view all the answers

What feature of a diamond can affect its polish when viewed at 10x magnification?

Polish mark Signup and view all the answers

What is the primary function of the pavilion facets in a diamond?

To reflect light and create brightness Signup and view all the answers

Which of these variations would indicate that a diamond is not symmetrical?

Table off-center Signup and view all the answers

What is indicated by an uneven outline of a diamond's girdle?

Out of round Signup and view all the answers

How is the pavilion depth percentage calculated?

As a percentage of the average girdle diameter Signup and view all the answers

What does a culet off-center condition reveal about the diamond?

The culet is not centered in the pavilion Signup and view all the answers

What effect does a steep pavilion angle have on a diamond's appearance?

Produces dark areas under the table Signup and view all the answers

What does the lower half length percentage represent in diamond grading?

The length of the lower half facets relative to total distance Signup and view all the answers

Which factor is typically related to crown angle variation in a round brilliant cut diamond?

Pavilion angle variation Signup and view all the answers

What is a sign of multiple symmetry variations in a diamond?

Out of round, misshapen facets, and pointing Signup and view all the answers

How is the girdle thickness percentage defined?

Thickness expressed as a percentage of the average girdle diameter Signup and view all the answers

Which statement best describes a laser manufacturing remnant (LMR)?

It is a surface imperfection from laser cutting Signup and view all the answers

What does a table/culet alignment issue indicate in a diamond's design?

Table and culet are displaced in opposite directions Signup and view all the answers

What likely occurs with a diamond that has variations in girdle thickness?

Inconsistencies where crown and pavilion meet Signup and view all the answers

Which factor relates directly to the appearance of a diamond's facets?

Symmetry of facet arrangement Signup and view all the answers

What does a total depth percentage exceeding 65 percent suggest about a diamond?

The diamond may have hidden weight due to overly thick features. Signup and view all the answers

Which of the following best defines 'polish' in the context of diamond quality?

The sharpness of reflections and clarity of light transmission. Signup and view all the answers

What are polish lines in a diamond?

Fine, parallel grooves left by the polishing process. Signup and view all the answers

The degree of visibility of a diamond's features when evaluated under magnification is a measure of what?

Finish quality. Signup and view all the answers

What does the presence of 'abrasion' look like on a diamond?

A series of minute scratches or pits along a facet junction. Signup and view all the answers

Which of these would indicate poor finish quality in a diamond?

Blemishes that affect the polish assessment. Signup and view all the answers

What is 'lizard skin' in relation to diamond blemishes?

A transparent, pitted texture with a wavy appearance. Signup and view all the answers

How can excessive heat during polishing affect a diamond's appearance?

It leads to a whitish haze known as 'burn'. Signup and view all the answers

What is a 'rough girdle' characteristic in diamonds?

An irregular or granular surface of a bruted girdle. Signup and view all the answers

What does good symmetry in a diamond mean?

All facets are precisely shaped and well positioned. Signup and view all the answers

What rating would a diamond receive if it has several small blemishes and slightly off-center facets?

Good Signup and view all the answers

Which of the following factors is least likely to affect a diamond’s cut grade?

Culet size Signup and view all the answers

In determining a diamond’s brightness, which combination of factors has the most impact?

Table percentage, crown angle, and pavilion angle Signup and view all the answers

What characteristic would likely lead to a fair rating for a diamond's finish quality?

Obvious polish lines and noticeable blemishes Signup and view all the answers

Which factor primarily determines the lowest cut grade for a diamond?

Lowest rated factor among all considered parameters Signup and view all the answers

What is the consequence of having a wavy girdle on a diamond?

It generally indicates a fair rating. Signup and view all the answers

Which statement about polish and symmetry is true for diamond ratings?

Noticeable pointing negatively impacts the rating. Signup and view all the answers

Which two factors can interact negatively to affect the cut grade of a diamond?

Table percentage and pavilion angle Signup and view all the answers

What aspect should be emphasized more than numerical parameters when evaluating a diamond?

Visible cleanliness and appearance Signup and view all the answers

If a diamond has numerous misshapen facets, what rating is most appropriate?

Fair Signup and view all the answers

Study Notes

Diamond Grading Proportions - Pavilion, Culet, and Finish

Pavilion: Diamond's pavilion facets reflect light from above back towards the crown, creating brightness and fire. Pavilion depth percentage measures the distance from the girdle to the culet as a percentage of the average girdle diameter. The pavilion angle is where the pavilion mains meet the girdle.
Estimating Pavilion Depth Percentage: Generally accurate for grading and appraisal. Identifying reflections from facets through the table can estimate the pavilion depth percentage. Variations in facet alignment affect reflected patterns.
Pavilion Depth Percentage & Angles: Steeper angles create darker areas under the table; shallower angles plus a large table can create unattractive reflections (e.g., fisheye effect). Higher pavilion depth percentage generally correlates with steeper angles.
Girdle, Lower Half Facets, and Culet:
- Girdle Thickness Percentage: The girdle's thickness as a percentage of the average girdle diameter. This measurement is important for evaluating the diamond's cut grade.
- Lower Half Facet Length Percentage: The length of the lower half facets in relation to the total distance to the culet (measured at 100%), evaluating for proper proportions.
- Culet Size: The culet facet at the bottom of the diamond where the pavilion meets the girdle. A pointed culet and its size are important for evaluating the cut grade. Imperfections at the culet, such as chips, reduce the estimate of pavilion depth percentage.
Calculations: Girdle thickness percentage is calculated by subtracting crown height and pavilion depth from total depth and rounding to 0.5%.
Cut Quality: Limitations of the pavilion's and the other facets affect the diamond's possible cut grade.

Design and Craftsmanship

Design: The diamond's physical shape including its proportions, durability, and weight.
Craftsmanship: The level of care that goes into the diamond's finishing details, and the overall polish and symmetry. Craftsmanship is important in determining aesthetic value.

Finish (Polish and Symmetry)

Polish: The overall condition of the diamond's facet surfaces. A well-polished diamond reflects light sharply and transmits it clearly. Imperfections, like abrasions and scratches, affect a diamond's polish rating.
Symmetry: Refers to exactness of diamond facet shape and placement. Assessments are based on its appearance when looking at it under magnification. Discrepancies in shape affect a diamond's symmetry rating.

Symmetry

Facet Alignment: Round brilliants have 58 perfectly shaped facets. Variations in placement of facets are common and usually don't significantly impact appearance.
Out of Round (OR), Table Offset (T/oc), Culet Offset (C/oc), Table/Culet Alignment (T/C): Girdle, table, and culet are not perfectly centered.
Girdle Thickness Variation, Crown Angle Variation (CV), Pavilion Angle Variation (PV): Variations in the measurements of crown and pavilion angles.
Crown Height Variation (CHV), Pavilion Depth Variation (PDV): Variations in the diamond's crown and pavilion depth measurements.
Star Angle Variation (SV), Star Percentage Variation (SPV), Upper Half Variation (UHV), Lower Half Variation (LHV): Variations among star and lower/upper half facet angles/lengths.
Missing Facet (MF), Extra Facets (EF), Natural (N): Facets that aren't standard according to the cut type and irregularities, respectively.
Non-Octagonal Table (T/oct): Deviation from the ideal eight-sided table shape.
Misshapen Facets: Facets that are not the correct size and shape.
Non-Pointing (Ptg): Facets that do not meet precisely at points.

Rating Polish and Symmetry

Excellent (Ex), Very Good (VG), Good (G), Fair (F), Poor (P): Specific gradings used for polish and symmetry. Excellent indicates high quality; Poor indicates significant issues.

Putting It All Together

The combination of all factors measured for Polish, Symmetry, and Design and Craftsmanship determine the final cut grade. The lowest score for any category in an assessment usually determines the final grade.
Factors like table percentage, crown angle, and pavilion angle are important for evaluating a round brilliant diamond's brightness.

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Description

Test your knowledge on diamond grading proportions, focusing on the pavilion, culet, and finish. Understand how the pavilion depth percentage and angles affect the diamond's brilliance and overall appearance. This quiz will cover essential concepts in grading and appraisal.