Cut and Value Flashcards
The pavilion angle is formed by the girdle plane and what else?
Pavilion main facets
What does a diamond’s finish consist of?
Symmetry and polish
What is the primary purpose of the culet?
Prevent chipping
What is the sparkle that occurs in a diamond when the gem, its light source, or its observer moves?
Scintillation
What is the balance of a finished gem’s facet known as?
Symmetry
On fancy shapes such as the oval or pear, what might variations in the pavilion angle cause?
Bow-Ties
What are the sides near the points of marquises, pears, and hearts called?
Wings
What is the separation of white light into its spectral colors?
Dispersion
What is the quality of the polish and prevision of the cut of a fashioned gemstone?
Finish
What is present in diamonds when an unattractive gray ring under the table?
Shallow pavilions
What do symmetry variations include?
Off-center tables and misshapen facets
What two things form the crown angle?
The girdle plane and bezel facets
The pavilion depth percentage is expressed as a percentage of what?
Average girdle diameter
If a marquise cut measures 9mm x3mm, what is it’s length-to-width ratio?
3:1
What do the angles and relative measurements of a polished gem and the relationships between them describe?
Proportions
What are the eight basic proportions of a diamond?
Girdle Outline, Table Size (Table Percentage), Crown Angle, Girdle Thickness, Pavilion Depth Percentage (Pavilion Angle), Total Depth Percentage, Culet Size, Length-to-Width Ratio (Fancy Shapes)
Where are the Star Facets located?
The first ring of facets around the table, directly touching the Table and the Bezel Facets.
Where are the Bezel Facets located?
The second ring of facets, touching the Star Facets and the Upper Half Facet.
Where are the Upper Half Facets located?
The third ring of facets, edges touching the Bezel Facets and the Girdle.
Where are the Lower Half Facets located?
The facets around the pavilion that connect from the Girdle to the Pavilion Main Facets.
Where are the Pavilion Main Facets located?
The facets around the pavilion that meet at the Culet and points up to the Girdle.
In most round brilliant table sizes, what is the range that reflects a compromise between weight retention and optical beauty?
Between 50% and 66%
What do most diamonds have crown angles between?
25 and 35
Bruted Girdle
An unpolished girdle on a diamond that should look frosted or waxy.
What is the Fisheye effect?
When the pavilions are shallower than 38%, and the girdle reflection forms an unattractive gray ring under the table.
When do stones look dark in the center?
When the pavilions are deeper than 49%.
What is a Nailhead effect?
When the pavilion depth is 50% or more and a dark area under the table is produced.
What are the most popular length-to-width ratios for Marquises?
Between1.75:1 and 2.25:1
What are the most popular length-to-width ratios for Ovals?
Between 1.33:1 and 1.66:1
What are the most popular length-to-width ratios for Emerald cuts, Rectangular Cushions, and Pears?
Between 1.50:1 and 1.75:1
What is the most popular length-to-width ratio for Hearts?
1:1
For round brilliants, most table percentages are:
50% and 60%
For round brilliants, most crown angles are:
25 and 35
For round brilliants, most pavilion depths are:
Between 42% and 44%
Total depth percentage is a combination of what three things?
Crown Height Percentage, Girdle Thickness Percentage, and Pavilion Depth Percentage
What aspect of a diamonds cut do most fancy cuts have, but most rounds don’t?
The culet
What are the eight primary factors that enter into an evaluation of a diamond’s polish?
Abrasions, lizard skin, nicks, pits, polish lines, burn marks, rough girdle, scratches
What are the eight symmetry variations?
Table or culet off-center, girdle outline out-of-round, facets that fail to point properly, misaligned crown and pavilion facets, table not a regular octagon, misshapen facets, extra facets, uneven outline
Average Girdle Diameter
The result achieved by adding the smallest and largest girdle measurements of a round brilliant and dividing by two.
Craftsmanship
The care that goes into the fashioning of a polished diamond, as confirmed by its finish.
Crown Angle
The angle formed by the bezel facets and the girdle plane.
Design
A diamond’s physical shape, including its proportions and durability, determined by decisions made during the fashioning process.
Dispersion
The separation of white light into spectral colors.
Finish
The quality of the polish and precision of the cut of a fashioned gemstone.
Girdle Outline
Face-up shape of a polished gem.
Length-to-Width Ratio
The comparison of the length to the width of a fancy-shaped diamond.
Make
The qualities of a faceted diamond’s proportions and finish.
Pavilion Angle
The angle formed by the pavilion main facets and the girdle plane.
Pavilion Bulge
larger-than-usual pavilion angles on the middle tier of facets, designed to add weight to a step-cut stone.
Pavilion Depth Percentage
The distance from the bottom of the girdle plane to the culet, expressed as a percentage of the average girdle diameter.
Polish
The overall condition of the facet surfaces of a finished diamond.
Proportions
The angles and relative measurements of a polished gem, and the relationships between them.
Refraction
The change in speed and possible change in direction of light as it travels from one transparent material to another.
Refractive Index (RI)
A measure of the change in the speed and angle of light as it passes from one material to another.
Shoulder
One of the two sides adjacent to the rounded end of a pear or oval shape.
Symmetry
The exactness of a finished gem’s shape and the placement of its facets.
Table Percentage (Size)
Table size expressed as a percentage of a round brilliant’s average girdle diameter.
Total Depth Percentage
Table-to-culet depth, expressed as a percentage of average girdle diameter.
Wing
One of the two sides near the point of a marquise, pear, or heart shape.
