Diamonds - The 4 C's
The method developed by the Gemological Institute of America determines quality based on the 4Cs.
Comments (Comments)
Under the "Additional Grading Information" an additional information could be indicated under certain circumstances, also called "Comments". This additional information contains further details, which also characterize the diamond, but of course also any other diamond, no matter which cut form. There are both negligible comments, as well as relevant, which can negatively affect the value of any diamond - such as so-called "Color Comments ". For example, if it says "High-Pressure-High-Temperature (HPHT for short), this indicates an artificial color enhancement; of course, a clearly value-reducing comment. The same applies to the addition "Clarity grade is based on a patch of color" - this means, in simple terms, that there is a patch of a different color in the diamond, which has a negative influence on the clarity of the stone. In addition, one does not want any "surface graining" or "internal graining" comments. These so-called Grainings are to be seen with the diamond either on the surface (thus Surface) or in the inside (thus Internal) with a 10x enlargement. These "Grainings" are caused by irregularities in the crystalline growth structure of the diamond and affect the transparency.
The gemologist recognizes fine lines inside the diamond which show graining (internal graining) or a similar structure on the surface of the gemstone (surface graining). The optical appearance under the microscope is similar to that of an extremely fine-grained, milky transparent sandpaper. The "Rapaport Specifications" for highest qualities (A1 and A2) do not accept diamonds with these characteristics (No Color Comment - No Graining Comment). From quality grade A3 on, the so-called "Grainings" are allowed, but the "Color Comments" are still not.
KEY TO SYMBOL
If a diamond is not flawless, but has inclusions or similar, each GIA certificate contains an additional section titled "Key To Symbols". This rubric shows which blemishes or inclusions are in the respective diamond. Here there are characteristics/inclusions that are considered so-called "allowed", i.e. do not negatively affect the value of a diamond, but there are also those that are undesirable.
Allowed, and therefore neutral are the following:
Pinpoint - A very small crystalline inclusion that is equivalent to a small dot.
Cloud - a small group of PINPOINTS that resemble a cloud
Crystal - Is a crystalline mineral inclusion inside the diamond.
Feather - Denotes a "feathery", slightly curved interruption in the mineral structure.
Needle - is a fine, elongated crystalline inclusion that resembles a small rod
Twinning Wisp - A group of PINPOINTS, CLOUDS or CRYSTALS which often appear in finest ramifications.