Chapter 12 - Key Words & Concepts Flashcards
What is the average girdle diameter used for?
It is the basis for comparing a diamond’s other proportions.
In what unit are diamonds always measured?
Millimeters.
What is the typical range for table percentages in most round brilliants?
About 55 percent to about 65 percent.
How do you determine a round brilliant diamond’s table size?
Measure the table facet in four directions and average the measurements.
What can help a cutter save weight from shallow rough?
A shallow crown.
What negative effect can a shallow crown have?
It can have a negative effect on appearance.
What should a diamond’s girdle thickness prevent?
Chipping.
What is a downside of having a girdle that is too thick?
It detracts from the stone’s appearance.
What can severe painting and digging out result in?
Hill positions of differing thicknesses and uneven scalloping around the girdle.
What can significant painting or digging out affect?
It can give a diamond an unattractive scintillation pattern or make it appear darker.
Fill in the blank: Most round brilliants have table percentages that range from about _______ to about _______.
55 percent to about 65 percent.
True or False: A diamond’s girdle should be as thick as possible to prevent chipping.
False.
What is the average girdle diameter?
The result achieved by adding the smallest and largest diameter measurements of a round brilliant and dividing by two.
What is the crown angle?
The angle formed by the bezel facets and the girdle plane.
Define crown height percentage.
The distance from the girdle plane to the table, expressed as a percentage of average girdle diameter.
What is digging out in cutting techniques?
A technique that thins the area of the girdle where the upper half facet junctions meet the lower half facet junctions, to retain weight or remove clarity characteristics.
What does girdle thickness refer to?
The width of a fashioned gem’s girdle.
What is painting in cutting techniques?
A technique that thins the area of the girdle where the bezel and pavilion main meet, to retain weight or remove clarity characteristics.
Define star length percentage.
The length of the star facets expressed as a percentage of the total distance between the girdle and the edge of the table facet.
What is a table gauge?
A transparent measuring device divided into millimeters and tenths of a millimeter, used to measure a diamond’s table.
What is table percentage?
A diamond’s table size expressed as a percentage of its average girdle diameter.
Define total depth percentage.
Table-to-culet depth, expressed as a percentage of average girdle diameter.
