Information about Diamond Grading

Clarity
Grading diamonds for clarity is used to classify 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 of pure or impure. In order to accurately classify clarity in polished diamonds we need to have several levels of clarity. GIA (Gemological Institute of America) has created a simple but detailed system of clarity grading.

Clarity	FL	IF	VVS1	VVS2	VS1	VS2	SI1	SI2	I1	I2	I3
Scale	Flawless-Internally Flawless		Very Very Slightly Imperfect		Very Sligtly Imperfect		Slightly Imperfect		Imperfect

FL-Flawless --- Stones with no imperfections inside or outside under the magnification of a 10X loupe.
IF-Internally Flawless --- Diamonds with no internal flaws and only small blemishes, mostly blemishes that can be removed by repolishing the stone.
VVS1 VVS2-Very very Slightly Imperfect --- Stones have very small inclusions which are very difficult to see even under a 10X magnification loupe.
VS1 VS2-Very Slightly Imperfect --- Stones have very small inclusions, which are somewhat difficult to see under a 10X loupe.
SI1 SI2-Slightly Imperfect --- Stones with inclusions, which are fairly easily seen under a 10X magnification loupe.
I1 I2 I3-Imperfect --- Stones with inclusions ranging from visible with naked eye to very easily seen from far with a 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 and external.

Types of Internal Flaws(Inclusions)
Pinpoints - A small whitish dot which is difficult to see. There can be a number of pinpoints together to form a cluster or a cloud of pinpoints.
Dark Spot - A small crystal inclusion or a thin flat inclusion that reflects the light like a miror
Colorless crystal - A small crystal of diamond, or sometimes another mineral
Cleavage - A crack that has a flat plane, and when struck in a certain direction could cause the diamond to split.
Feather - Another name for a crack, which is not dangerous is small and not open through a facet.
Bearding or girdle fringes - Due to hastiness in the shaping process when giving the diamond its initial cut.
Growth or grain lines - Can only be seen when rotating the diamond slowly while looking at it which 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(Blemishes)
Natural - Usually occurs on the girdle and looks like a rough, unpolished area. Also 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 - A small chip, usually on the girdle and can be cause by wear. Sometimes a nick or chip can be seen on the edge of a facet.
Girdle roughness - Appears as crisscrossed lines, and can be removed by repolishing.
Pits or cavaties - Pits or holes on the table facets
Scratch - Usually a minor defect that can be removed by 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.