Understanding the GIA Diamond Grading Report
How to Determine the Quality of a Diamond
National Gemstone markets diamonds with GIA Grading Reports. The GIA was formed in 1931 and is a non-profit institution. They do not buy/sell or appraise diamonds. They are an educational and research institute. Please note, a diamond graded by a person who graduated from the GIA is not the same as a GIA Grading Report. Do not buy a diamond from anyone who grades and sells it. There is too much temptation to over-grade the diamond. The GIA operates like a neutral intermediary between the buyers and sellers.
- Carat Size: 1/2 carat (.50 points) or larger
- Color: D-H
- Clarity: Slightly Included Two (SI2) or better
- Depth: 56-62%
- Table: 52-62%
- Girdle: Minimum Variations, No Extremely Thin or Extremely Thick
- Culet: None, Small or Medium
- Polish and Symmetry: Good or better
- Fluorescence: None or blue is fine. Stay away from orange, yellow, and green.
Shape and Cut
Each diamond is described as to its shape (round, oval, pear, etc.) and its cut (brilliant, etc.)
Diamonds are weighed on an extremely accurate digital balance. One carat equals 100 points, which weigh 1/5 gram.
The items in this category relate to the cut (or make) of the diamond:
- Depth Percentage: The relationship between the depth and the average diameter of a diamond.
- Table: The relationship between the table (flat, top facet) and the average diameter.
- Girdle: Describes the variance and relative width at minimum and maximum positions. The girdle is the rim that separates the top and the bottom of the diamond.
- Culet: The bottom facet of a diamond as viewed through the table.
- Polish: Refers to the quality of the surface of a diamond.
- Symmetry: General comment regarding the symmetry of the diamond.
Clarity / GIA Clarity Grading Scale
|INTERNALLY FLAWLESS||VERY,VERY SLIGHTLY INCLUDED 1 AND 2||VERY SLIGHTLY INCLUDED 1 AND 2||SLIGHTLY INCLUDED 1 AND 2||INCLUDED 1, 2 AND 3|
Clarity refers to the summation of the number, size and placement as well as the nature of inclusions and/or surface irregularities. Flawless stones are diamonds free of inclusions under 10 power. Internally flawless are diamonds without any internal inclusions. VVS1 and VVS2 have extremely small inclusions. VS1 and VS2 possess small inclusions. SI1 and SI2 have inclusions that can be seen easily under 10 power magnification, but are not usually visible to the naked eye. I1, I2, and I3 have large inclusions that are visible to the naked eye.
Color Grade / GIA Color Grading Scale
|COLORLESS||NEAR COLORLESS||FAINT YELLOW||VERY LIGHT YELLOW||LIGHT YELLOW|
Color refers to the absence of color in a diamond. The less yellow within the diamond, the higher on the alphabetical scale the diamond will be graded. Colorless diamonds are D-F, near colorless are G-J, faint yellow are K-M, very light yellow are N-R. S-Z are light yellow.
Fluorescence describes the degree of sensitivity of a diamond to long wave ultraviolet radiation.
No Appraisals or Valuations
The GIA objectively grades only, it does not place a valuation on the stone in its grading report.
For more information, visit GIA's internet site.