The clarity scale and diamond grading system of the Gemological Institute of America (GIA) were developed in 1953 by Richard T. Liddicoat and associates. There are six categories and eleven diamond clarity grades on the GIA diamond grading system.

1. I1, I2, and I3 Included Diamonds: I clarity diamonds have noticeable inclusions that will probably be seen and affect their beauty 
2. SI1 and SI2 diamonds: are classified as slightly included (SI) diamonds. They may be identified at 10x magnification. If the eye is clear, SI diamonds are usually the greatest value. SI2 inclusions may be seen by an unassisted, sharp eye, especially when viewed from the side. 
3. VS1, VS2 Very Slightly Included (VS) Diamonds: Minor inclusions visible at 10x magnification, ranging from challenging (VS1) to somewhat easy (VS2).  
4. VVS1, VVS2 Very, Very Slightly Included (VVS) Diamonds: VVS clarity is uncommon and produces an eye-clean appearance. Features are minute and challenging to see under 10x magnification, even for trained eyes. 
5. Internally Flawless (IF) Diamonds: May have a few minor surface imperfections that are detectable under a microscope. Only surface features determine the grade for IF diamonds; no impurities within the stone. 
6. Flawless diamonds (FL): have neither internal nor exterior flaws, and less than 1% of all diamonds have FL clarity. Because it is practically hard to locate a diamond that is 100% devoid of inclusions, perfect diamonds are extremely rare. 

The way a diamond is graded and assigned a "score" on the diamond clarity chart is mostly influenced by five criteria. The size, kind, quantity, placement, and relief of the inclusions are the five factors that go into diamond grading.

1. Size: One of the most crucial elements in establishing a diamond's clarity grade is the size of its inclusions. The influence of inclusions on a diamond's look increases with its size.
2. Nature: The term "nature" describes the kinds of inclusions that are visible in the diamond as well as their depth.
3. Number: The quantity of inclusions a diamond has is another factor considered by grading organizations. A diamond's clarity and look can be greatly affected by a significant number of imperfections, no matter how little. 
4. Location: An inclusion's position describes where it is situated inside the diamond. The inclusion will be more noticeable to the eye and have a greater influence on the clarity grade if it is located closer to the table's center.
5. Relief: To put it simply, the relief is the amount of contrast between the inclusions and the diamond, or how prominent the inclusions are in relation to the diamond. Diamond grading may be impacted by how deeper the color appears in relation to the relief.

There are several forms of inclusions that can alter a diamond's look, even though the term "inclusion" is frequently used to describe any kind of flaw in a diamond.

The most prevalent inclusion types and the impact they can have on a diamond's clarity are listed below:

• Cloud: A cloud is really a collection of tiny, closely spaced pinpoints rather than a single flaw in a diamond. A cloud may make a diamond appear dull and foggy, which reduces its brightness. A diamond is said to be hazy if it has several big clouds.
• Graining: Uneven crystal formation leads to the development of this kind of internal inclusion. A diamond with graining will have internal lines that are white, colored, or reflective and will seem quite fuzzy.
• Cavity: A diamond's surface dents or fractures are known as cavities. Depending on the kinds of minerals present in the diamond, they may seem colorless or colored. If the cavity's crystal inclusions are colored, their appearance will be considerably more noticeable, and the unassisted eye will most likely be able to perceive them.
• Feather: Feathers are tiny fissures that, as their name implies, resemble feathers when viewed from specific perspectives. While some feathers are clearly visible, others are almost perceptible. Diamond feathers may reflect light and look clear, or they can absorb it and appear white.