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A Guide to Diamond Polish

The final stage of polishing gives each Diamond the smooth glass-like surface helping to reflect light from the stone. The assessment of polish takes into consideration the amount and visibility of features The assessment of these features under laboratory conditions helps graders determine the polish grade for each certified Diamond. 

Excellent Polish

No minor polish features to few minor polish features. Minor polish features are viewed by an expert with difficulty under 10 x magnification. 

Very Good Polish

Minor polish details are seen by an expert eye under 10 x magnification. 

Good Polish

Magnification under 10 x loupe reveals noticeable polish features. Viewed with the naked eye, the lustre of the Diamond may be affected. 

Fair Polish

Obvious heavier polish features are clearly visible under 10 x magnification. Diamond lustre is reduced when viewed with the naked eye. 

Poor Polish

Significant polish features are easily seen under 10 x  magnification. Diamond lustre is significantly affected when viewed with the naked eye. 

Polish Features

During the assessment of polish, the following features may be visible on some Diamonds. 

Tiny openings appearing as dots.

Fine surface scratches.

Burn marks- appearing as a cloudy milky coating on the surface of the Diamond.

Nick- small notches seen at the junction between two facets without any visible depth at 10 x magnification.

Lizard Skin - uneven surface across one facet caused by polishing the Diamond against the natural grain of the stone.

Rough Girdle - small pits and nicks appearing on a bruted girdle.

Abrasions - scuffed facet edges which reduce the sharpness of edges between two facets.