The Gemological Institute of America, referred to as GIA, was established in 1931 and is the world’s authoritative diamond and colored gemstone research institution. As a not-for-profit institution, GIA has rigorously defined standards of gem and jewelry knowledge. Gemstone clarity is graded by number and code. Jewelers and gemologists often use the meaning of these codes to understand the ‘GIA Gem Clarity Grading Code’.
GIA Gem Clarity Grading Code
Let’s Understand Gem Identification Better
GIA Diamond Clarity Standard
GIA Diamond Clarity Standards are divided into 6 categories, they are:
|1||FL||Flawless||A diamond without any inclusions or blemishes when viewed at 10X.|
|2||IF||Internally Flawless||Observed under 10X, there are no inclusions inside the diamond.|
|3||VVS1 , VVS2||Very Slightly Included Grade||Observed under 10X, there are extremely tiny inclusions inside the diamond, which are difficult to see even for professional appraisers.|
|4||VS1 , VS2||Slightly included||When observed under 10X, there are tiny inclusions inside the diamond.|
|5||SI1 , SI2||Slightly included||When observed under 10X, there are tiny inclusions inside the diamond.|
|6||I1， I2 , I3||Included grades||Observed under 10X, the blemishes are visible and may affect the transparency and brilliance of the diamond.|
Interpreting GIA certificate information
- Date: the date when the GIA certificate was issued.
- GIA Report Number: This number is the laser code etched on the gem.
- Shape and Cutting Style: Describes the shape of the cut.
- Measurements: Gemstone diameter (minimum-maximum) size X height dimension.
Diamond grading reports
There are two types of diamond grading reports issued by GIA: Reports issued for diamonds smaller than 1 carat. The other is a certificate issued for diamonds over 1 carat (including 1 carat).
- Carat Weight: Carat is the unit for calculating the weight of diamonds, 1 carat is equivalent to 0.2 grams.
- Color Grade: Through the comparison of professional diamond master stones, the diamond color is divided into 23 grades from D (transparent and colorless) to Z (light yellow).
- Clarity Grade: According to the number of inclusions and the obvious position of diamond inclusions, it is divided into 11 grades of FL-I3.
- Cut Grade: It can be divided into Excellent, Very good, Good, Fair, and Poor grades.
- Polish: Polishing can increase the brightness of diamonds, which can be divided into Excellent, Very good, Good, Fair, and Poor grades.
- Symmetry: Refers to the symmetry of the diamond cut. Diamonds above Good may have hearts and arrows. There are excellent (Excellent), very good (Very good), good (Good), average (Fair), and poor (Poor) grades.
- Fluorescence: The intensity of diamond fluorescence. It is divided into no fluorescence (None), slight fluorescence (Faint), medium fluorescence (Medium), strong fluorescence (Strong), and very strong fluorescence (Very Strong).
- Clarity Characteristics: The shape representation of the diamond’s internal features observed under the microscope.
- Inscription(s): The laser code engraved on the waist of the diamond, consistent with the GIA Report Number.
- GIA Report Number: the same as the gemstone waist laser code
- Proportion: Describe the detailed proportion of each part of the cut.
GIA cutting ratio
The cutting ratio on the GIA certificate includes: Total depth percentage, Table percentage, and Girdle proportion:
- Total depth percentage: The percentage of diamond height and relative girdle average diameter, the ratio is 58% – 62% is the most ideal.
- Table percentage: The percentage of the table width relative to the average diameter directly determines the fire and brightness of a diamond, which is very critical. Diamonds with smaller tables have more fire.
- Girdle proportion: If the diamond is too thin, it will be unstable; if it is too thick, it will affect the brightness.
- GIA Color Scale: GIA divides the color of diamonds into 23 grades with English letters D to Z, representing the color grade of diamonds from completely colorless to light yellow or light brown.
- GIA Clarity Scale: diamond clarity grade, judged by 10 times magnifying glass observation.
- GIA Cut Scale: Refers to the comprehensive evaluation of the diamond cutting process, which is only described on the certificate of round diamonds.
The above is about the GIA grade information and GIA certificate interpretation introduced by Normaltan Jewelry. Hope you have a better understanding of GIA.