Grading diamonds for clarity is the process for classifying the imperfections, both internal and external. Imperfections are called inclusions when internal and blemishes when external. The term clarity is preferred over purity because purity has a very narrow definition pure or impure. In order to accurately classify clarity in polished diamonds we need to have several levels of clarity. GIA has standardized a simple but detailed system.
FL-Flawless – These stones have no imperfections inside or on the outside of the stone under the magnification of a loupe of 10X magnification.
IF-Internally Flawless – This grade is awarded to diamonds with no internal flaws and only minor external blemishes. Nicks pits or girdle roughness, not on the table, which could be removed in re-polishing.
VVS1 , VVS2 – Very Very Slightly Imperfect – These stones have very, very small inclusions, which are extremely difficult to see under a loupe of 10X magnification.
VS1, VS2 – Very Slightly Imperfect – These stones have very small inclusions, which are slightly difficult to see under a loupe of 10X magnification.
SI1,SI2-Slightly Imperfect – These stones have inclusions, which are fairly easy to see under with a 10X magnification, and can be seen with the naked eye.
I1, I2, and I3-Imperfect – These stones have inclusions ranging from eye visible to very easily seen to the naked eye.
Flaws are caused by a shift in the pressure and or temperature during the time when the diamond is being formed. There are many types of imperfections, internal inclusions and external flaws.
Types of Internal flaws or Inclusions
Pinpoints – A small usually whitish dot that is difficult to see. There can be a number of pinpoints – cluster -or a cloud of pinpoints.
Dark Spot – A small crystal inclusion or thin flat inclusion that reflects the light like a mirror.
Colorless crystal – This is a small crystal of diamond, and sometimes-another mineral.
Cleavage – A small cleavage is a crack that has a flat plane, which if struck in a certain direction, could cause the diamond to split.
Feather – This is another name for crack. A feather is not dangerous if small and does not open through a facet.
Bearding or girdle fringes – Result from hastiness in the bruiting process when giving the diamond its initial shape in the cutting process.
Growth or grain lines – These can only be seen when rotating the diamond slowly during examination. They appear and disappear usually instantaneously and will appear in groups.
Knaat or twin lines – Slightly raised dot with a trail resembling a comet.
Laser treatment – A laser is used to make flaws less visible. A black spot can be vaporized and will disappear leaving a void in the diamond.
Types of External flaws or Blemishes
Natural – This usually occurs on the girdle and looks like a rough, unpolished area. A natural is a remnant of the original skin of the diamond. Indicates a shortage of rough or that the cutter made the largest acceptable diamond from the material he had to work with.
Nick – This is a small chip, usually on the girdle and can be caused by wear. Sometimes a nick or chip can be seen on the edge of a facet.
Girdle roughness – This blemish appears as crisscrossed lines, and can be removed by re-polishing.
Pitts or cavities – Pits or holes on the table facets.
Scratch – A scratch is usually a minor defect that can be removed by re-polishing.
Polishing lines – Many diamonds exhibit polishing lines and are the result of badly maintained polishing wheels.
Abraded or rough culets – The culet has been chipped or poorly finished.
The clarity grade can have a significant effect on the value of a diamond. The price variance between an Internally Flawless diamond and a Very Slightly Included One diamond clarity grade is significant at the wholesale level. The chart below illustrates the shift in pricing.
Price movement by clarity grade for highest quality diamond while holding all other quality classifications constant. Prices are New York 47th Street Wholesale Prices 12/27/02