The 4 C's -Diamond Clarity - What are Inclusions and Blemishes?
Diamond Clarity Grading: An Overview
One of the most confusing aspects of Diamond grading amongst purchasers is often Clarity, which describe phenomena called "inclusions" and "blemishes". These can be thought of as birthmarks within the stone, resulting from variations in heat and pressure over millions of years during the stones formation deep within the earth.
This article will go through the various types of inclusions & blemishes, briefly describing them. In general the less inclusions/ blemishes a diamond has, the higher its clarity grading will be and vice versa. However when a stone is graded, the degree to which clarity is impacted will also be affected by the position, type and size of the inclusion, making the grading process somewhat more complex.
Inclusions refer to internal phenomena within the stone whereas blemishes allude to external flaws at the surface of the diamond
GIA Diamond Clarity Grading System
The GIA has a 6 point grading system for clarity and this is summarised in the table below:
| Grade | Description |
| FL | "Flawless"; no inclusions or blemishes under a loupe at 10x magnification |
| IF | "Internally Flawless"; no inclusions visible under 10x magnification |
| VVS1 & VVS2 | "Very Very Slight Included"; Inclusions so slight they are difficult for a skilled grader to see under 10x magnification |
| VS1 & VS2 | "Very Slight Included" ; Inclusions are observed with effort under 10x magnification, but can be characterised as minor |
| SI1 SI2 | "Slightly Included" ; Inclusions are noticeable under 10x magnification |
| Included (I1, I2 I3) | "Included"; Inclusions are obvious under 10x magnification which may affect transparency and brilliance |
Surface Anomalies or Blemishes
Bearding
This describes fuzzy white lines that extend from the outer surface of the diamond inwards, significant bearding in the girdle area can cause fuzzy or grey appearance of the overall appearance of the diamond
Cavity
An indentation on the surface of the diamond usually occurring during the cutting process, where an internal inclusion is exposed. A cavity can trap external pollutants such as dirt and grease causing discolouration over time
Chip
Like a cavity a surface indentation, typically found near the girdle of the diamond, but due to wear and tear as opposed to the polishing process.
Internal Anomalies or Inclusions
Clouds
Pinpoint crystal type anomalies of various sizes, depending on size and location can affect the brightness and light transmission properties of the diamond. Small diffuse clouds are unlikely to cause issues but big dense clouds can affect appearance.
Crystal
Mineralisation or crystallisation within the diamond that can be various colours; colourless, black, red, or green. Coloured crystal inclusions are deemed less desirable.
Feather
A small fracture within the diamond which will typically appear transparent or a white feather like appearance should it catch the light. Feathers closer to the surface can cause fractures and discolouration and should be avoided
Grain
Internal graining can appear milky or hazy and is caused by irregular crystal growth during diamond formation. This phenomena if significant can cause a crease or reflection like appearance
Knot
A white or transparent crystal at the surface of a polished diamond
Needle
A long thin needle-shaped inclusion that is usually white or transparent in colour and visible at 10x magnification. If they appear in clusters, it might have a detrimental effect on the diamond’s clarity
Pinpoints
These are very small white or black crystals that are embedded inside a diamond. These internal crystals look like a small dot, visible at 10x magnification.
Twinning Wisps
This inclusion is a series of pinpoints, clouds, or crystals that form while a diamond is growing. During a diamond’s formation process, it may stop growing due to unfavourable conditions and twinning wisps are formed when growth restarts in a different direction, sometimes thousands of years later.
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Images courtesy of GIA; https://4cs.gia.edu/en-us/blog/diamond-inclusions-defined/