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Graining anyone?

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Diamond Explorer

Sep 7, 2008
Graining has to do with the crystal structure of the individual diamond. Its almost never a cause for alarm and rarely affects transparency. I found a more detailed description on

Internal Graining: The comment on a lab report indicating "Internal Graining Not Shown" should not be reason for alarm because it refers to a clarity characteristic which is usually not readily visible without the use of extremely high magnification. Internal Graining should not be considered an "absolute characteristic" because the visibility depends on the lighting conditions and the specific angle by which the diamond is being evaluated. It might be visible to an experience diamond grader who is examining the diamond under laboratory conditions, but may never be detected by other people. Essentially internal graining refers to part of the grain structure of the diamond which was visible as a kind of transparent line to the grader. The degree of the visibility of the grain lines will have an effect upon the clarity grade of the diamond and if no other clarity characteristics are present then the graining may be the basis for the clarity grade of the diamond. For instance, a diamond that contained small diamond crystals which by themselves would warrant a clarity grade of VS-1 might be graded as a VS-2 if internal graining were present. However another diamond that did not contain the diamond crystals might be graded as VVS-2 if the grade is based upon internal graining and the comment "clarity grade based upon internal graining" would appear under the "comments" section of the lab report while nothing is indicated under the "keys to symbols" by the plotting diagram.

Surface Graining: The comment on the lab report referring to "Surface Graining Not Shown" sounds kind of serious but it really isn''t... Surface graining is essentially a transparent line that is part of the grain of the diamond which happens to be visible across a facet junction. It is essentially the same thing as Internal Graining but it resides on the surface of the diamond instead of being within the crystal structure of the stone. If the surface grain line were within the structure of the facet and not crossing over the facet line it wouldn''t be mentioned on the lab report because it would be considered a characteristic of polish. Most surface graining is so insignificant that we are rarely able to find it and when we do it is because we are using extensive magnification like 50 - 70x which is substantially higher than the industry standard of 10x which is supposed to be used for diamond grading. In the case of a diamond graded as Internally Flawless in clarity, as a general rule it is likely that the diamond may have been graded as Flawless instead of Internally Flawless if the surface graining were not present.
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