Diamond Polish Grading
Diamond polishing is one of the factors that affect cut quality of diamond, other factors being
symmetry of facets.
So, it is important in understand about diamond polishing in order to understand cut quality of diamond.
Diamond Polishing is graded on the basis of:
- Visibility of polishing lines on the surface of the diamond. Lesser
are the polishing lines, it means superior is the polish grade.
- Presence or absence of burnt facets.
Almost, all cut diamonds show polishing marks. But these lines are very fine and can be seen only by 10X or more magnification.
Polishing lines are formed during cutting
process of diamond. These marks are the result of a diamond’s hardness
being dependent on crystallographic directions. Hardness of each facet
of diamond is different from other.
Since, cutter can set only one facet on
the polishing wheel at a time, direction of polishing marks is same
throughout a facet but their directions change with different facets.
Polishing lines can be seen when viewed from opposite side of the diamond. Polishing marks on the table of a diamond can be seen though the pavillion. If the relevant surface is slightly tilted and slowly moved under the light, the marks are visible in the reflected light. Polishing lines adversely affects the
brilliance of diamond and reduces its transparency.
|Polishing Lines on Table
Diamond Polish Grades
Based on quality of
polish, diamond is graded under following five categories:
- Ideal/Excellent: Under this category, diamonds with hard to find polish line seen with great difficulty under 10X magnification are included.
- Very Good: Under this category, diamonds with only faint polish lines that do attract attention under 10X magnifications are included.
- Good: Under this category, diamonds with various small transparent polish lines visible through 10X magnifications are included.
- Fair: Under this category diamond with obvious
transparent or slight colored polish lines or burn marks visible through
10X magnification are included. Luster of diamond is affected when
viewed through unaided eye.
- Poor: Under this category, with prominent polish
lines and marks are easily visible under 10X magnification. Luster of
diamond is significantly reduced and it is noticeable with unaided eye.
Important considerations while choosing between different Polishing Grades
- If you are considering buying diamond, always choose "good" polish grade diamond, if the diamond is of VS or SI clarity.
- Diamonds with excellent and very good
grades are expensive but there is no noticeable difference in luster of
diamond as compared to diamond with "good" polish grade when seen
through unaided eye.
- Also, do note that if you are considering diamonds with Flawless
clarity, choose "excellent" or "very good" polish grade. This is because, in flawless clarity even a very minute polish mark is
easily visible due to high clarity. If you choose the "fair" or "poor"
polish grade, brilliance of diamond will be noticeably reduced.
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