AGA Rules for Determining Cut Grade
The determining
factors of the AGA-Cut Grade
revised 4/16/02
1A grade:
All characteristics
are best when 1A, but may include a single 1B characteristic. You pay
a premium for this cut and you should insist on getting exactly what you are
paying for.
1B grade:
All characteristics
need to be all 1B or 1A to 2B. Only a single class 2 characteristic is permitted.
The class 2 characteristic should be within 2% or 2 degrees of the 1B characteristic.
2A grade:
All characteristics
need to be 2A or 1A thru 2B. Only a single 2B parameter is permitted and it
must be within 2% or 2 degrees of the 2A characteristic. (crown angle degree
rounds only)
2B grade:
All characteristics
need to be all 2B or 1A thru 3A. Only a single 3A characteristic is permitted
and the 3A characteristic cannot be a very thick girdle or more than 1 degree
too shallow a crown angle. The 3A characteristic must be within 2% or
1 degree of the 2B characteristic. (crown angle degree rounds only)
3A grade:
A stone may be
all 3A or 1A thru 4A. Any characteristics of 4A must be within 2% or 1 degree
the 3B characteristic. More than a single 4A characteristic and the stone cannot
grade 3A. An overall class 4 girdle thickness cannot grade 3A overall.
An overall girdle thickness is NOT determined by a single thin or thick area
of a girdle. "Overall" has a meaning equivalent to "the major
portion." (crown angle degree rounds only)
3B grade:
As stone may be all 3B or
1A thru 4B. Any single characteristic of grade 4B must be within 2% or 1 degree
of the 4A measurement. Only one class 4 characteristic permitted. Stones
with class 4 extremely thick or extremely thin over all girdles may not be graded
overall 3B. (crown angle degree rounds only)
4A grade:
A stone may be all 4A or 1A thru 4B. Only two 4B characteristics
are permitted at most. (crown angle degree rounds only)
4B grade:
Is all 4B or may be any
combination from 1A thru 4B. Stones with more than two 4B characteristics are
automatically 4B.
SPECIALTY
CUTS:There
are diamonds that do not conform to the classic shape cut parameters and must
be considered on an individual basis.
ONE
CANNOT GRADE UNUSUAL CUT DIAMONDS SOLELY ON ARBITRARY PARAMETERS. EXPERIENCE
IN EXAMINING DIAMONDS FOR EFFECTIVE AND PRECISE CUTTING IS REQUIRED FOR CUTS
NOT COVERED IN THE THREE CHARTS OF TYPICAL STANDARD CUT DIAMONDS.
Courtesy of Dave
Atlas
http://www.gemappraisers.com
For more information concerning AGA,
please feel
free to contact David Atlas
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