Types of Diamond Imperfections

Diamonds basically have two types of flaws. They are categorized as:

·        Inclusions or Internal Flaws.

·        Blemishes or external Flaws.

These two flaws are further sub-divided into various categories. Let us explain some of these flaws here so that you would be able to get a fair understanding of the Diamond imperfections.

Pinpoint – This is usually a whitish (sometimes dark) dot that small and difficult to see. A group of these pinpoints is considered to be a cluster of pinpoint flaws and cannot be categorized as VVS. These clouds of pinpoints are hazy & not usually seen easily.

Dark Spot – This is defined as a thin, flat inclusion or a small crystal inclusion, which reflects light similar to a mirror. This defect could also appear as a metallic and silvery reflector.

Colorless Crystal – This is usually a small crystal of diamond and could also be of another mineral. Though it is usually small, sometimes it could be large enough to substantially decrease the flaw grade to SI₂ or even I₁. The grade of the stones could be reduced from possible VS₂ to I₃ due to the presence of a small group of colorless crystals.

Feather – A crack in the stone is usually known as Feather. A feather is not considered to be dangerous incase it is small and does not break out through a facet. These could become large if they are subjected to a Thermo-shock or cleaned by ultrasonic means.

Growth or grain lines – These are usually observed when the diamond is slowly rotated for the purpose of examination. These usually appear as a group of two to four pale brown lines and they instantaneously appear and disappear. These lines will not affect the grade adversely if they are small and cannot be seen from the crown side of the diamond.

Laser Treatment – This is used widely these days to make the less visible while improving the aesthetics of the stone. A Black spot on a stone can be practically removed when subjected to this kind of treatment. But, these laser holes can be spotted under a 10x magnification appearing like straight fine white threads.

A small natural  - These usually appear to be like a rough, unpolished area and mostly occur on the girdle. They look like scratch lines or small triangles called trigons. Many times, when these naturals occur below the girdle edge, they are polished making them look like an extra facet. A natural is usually the left over portion of the original skin of the diamond, and is mostly left on the girdle, which shows that the cutter tried to cut the largest possible diameter from the rough.

Nick – This is usually found on the girdle as a small chip, which is a result of wear especially if the girdle has been proportioned on the thin side. Generally the chip or nick is found on the facet edges where they meet. This is mainly seen on the crown and if found to be small, the bruised corner could be polished thereby creating an additional facet.

Girdle roughness – This defect appears as criss-crossed lines being slightly chipped and having a brighter and duller finishing. Repolishing or faceting could correct these defects.

Cavities or Pits – These defects, if found to be deep on the table facet would reduce the stone grade. Pits could be removed be re-cutting the whole top of the stone and could also result in the diameter of the stone being reduced.

 Scratch – These are considered to be minor defects that can be removed by simple repolishing. However, care must be taken to remove the stone from its setting and again reset it after the polishing is complete.

Polishing lines – Polishing lines are found on many Diamonds. These do not decrease the stone value incase they appear on the pavilion side and are not very obvious. But, these lines are prominent in some small diamonds as a result of the polishing wheel not being properly maintained.

Abraded or rough culet – This is considered to be a minor flaw when the culet has been poorly finished or chipped.

It is a necessity to scan the diamond for the number as well as the nature of internal characteristics along with their size and position in order to grade its clarity  

This type of analysis is done using the IGI scope along with a loupe 10x by laboratory gemologists having a good amount of experience.  A diamond is considered to be “ Internally Flawless” if it reveals no internal defects when examined under 10x magnification.

Internally Flawless	Very Very Slightly Included	Very Slightly Included
Free from internal blemishes visible under 10x magnification (small external details tolerated).	Inclusions and/or external blemishes very difficult to locate under 10x magnification.	Inclusions and external blemishes difficult to locate under 10x magnification.

Slightly Included	Imperfect	Imperfect	Imperfect
Inclusions and external blemishes easy to locate under 10x magnification.	Inclusions and external blemishes hard to locate with naked eye.	Inclusions and external blemishes easy to locate with naked eye.	Heavy inclusions very easy to locate with the naked eye.