When the polish of the stone is not good it affects the brilliancy, the fire and especially the luster of the stone.
There are 3 defects that can affect the polish:
- Polish Lines – Fine parallel grooves and ridges left by polishing; can occur on any facet but do not cross facet junctions; transparent or white.
- Burnt areas – Hazy surface area that results from excessive heat during polishing; also called a burned facet.
Polish lines and burnt areas can be easily fixed by polishing the stone.
You should always look for polish lines and burnt areas from the area of the stone opposite to where they are. This means that to see polish lines and burnt areas in the pavilion, one must look through the crown, and to see polish lines and burnt areas in the crown, one must look through the pavilion.
- Scratches and Abrasions.
- Nick – A small notch on a facet junction
- Pit – A small opening that looks like a tiny white dot
- Checking polish in the microscope:
If you want to check the polish in the table, you should put the stone between the culet and the table, tilt it towards yourself until the table looks like a black background and the star facets look fully focused. You should turn the stone 360 degrees and look for polish lines, burnt areas and scratches on the black background, which is the table.
It is also possible to check polish problems directly on the facet using the reflective light system.
Rules for determining the polish grade
- If there are no polish problems the grade is: Excellent.
- If there are few scratches or polish lines the grade is: Very Good.
- If there is a medium amount of scratches or a medium amount of polish lines or very light burnt areas the grade will be: Good.
- If there are burnt areas that are easily seen by the Loupe the grade will be: Fair.