POLISH
A number of features are considered in the evaluation of
polish. Examples and definitions of these are provided in
table 1,Polish Features, on page 83.
Diamond graders consider the amount and visibility of
the polish features present.The general appearances of GIA’s
five polish categories are described here.
Excellent: ranges from no polish features to a few
minute polish features that can be viewed with difficulty
face-up at 10X magnification.*
Very Good: minor polish features are seen face-up at
10X magnification.Good: noticeable polish features are seen face-up at
10X magnification.The luster of the diamond may be
affected when viewed with the unaided eye.
Fair: obvious heavy polish features are seen face-up at
10X magnification.The luster of the diamond is affected
when viewed with the unaided eye.
Poor: prominent heavy polish features are seen faceup
at 10X magnification.The luster of the diamond
is significantly affected when viewed with the
unaided eye.
As with all other aspects of diamond grading, standard
methodology and a controlled environment are used to
evaluate polish consistently, with the final determination
based on an objective consensus of independent grader
opinions.The following steps are performed at 10X magnification
with either a fully corrected loupe or gemological
microscope under darkfield illumination to assess the
polish:
• The diamond is first examined face-up, girdle-to-girdle
to gain an initial impression of the polish.
• The diamond is then examined one section at a time,
through both the crown and pavilion, to locate and
identify the specific polish features present.
• The diamond is again examined face-up,girdle-to-girdle,
and this time viewed in at least four different positions
with a loupe;some features may be more or less apparent
depending on the orientation of the diamond.
• A visual polish description is assigned that considers
the diamond’s overall face-up appearance as well as
polish features seen in any view. Emphasis is placed on
the diamond’s face-up appearance with a 10X loupe.
SYMMETRY
As with polish,a number of features are considered in the
evaluation of symmetry;these are defined and illustrated in
tables 2 and 3 on pages 84-85. Symmetry features can be
subdivided into two categories:proportion related (see table
2,Proportion-Related Symmetry Features) and facet related