Since its founding in 1931, the Gemological Institute of America (GIA) has been the world’s most authoritative gemological and educational institution. Its “4Cs” grading system—Color, Clarity, Cut, and Carat—has become the common language for evaluating diamond quality globally.
However, with the booming development of the lab-grown diamond market, GIA announced a historic innovation in 2025: it will no longer use the traditional 4C standard, but will adopt a brand-new “Premium/Standard” two-tier grading system, officially establishing a dedicated evaluation system for lab-grown diamonds.
Table of Contents
What are lab-grown diamonds?
Lab-grown diamonds are produced in a laboratory using either high-pressure high-temperature (HPHT) or chemical vapor deposition (CVD).
These diamonds have the same chemical composition, crystal structure, and optical properties as natural diamonds. They are all made of pure carbon (C) and have the same hardness (10 Mohs) and refractive index (2.42).
The only difference lies in their manufacturing process:
- Natural diamonds originate from deep within the Earth’s crust and take billions of years to form.
- Lab-grown diamonds are grown by humans using scientific and technological methods in a short period of time.
This controlled production method makes lab-grown diamonds more affordable, while also possessing environmental and ethical value, thus gradually gaining market favor.
GIA’s traditional 4C grading system
The 4C grading system developed by the GIA (Gemological Institute of America) is the global standard for diamond evaluation, which includes four major aspects: Color, Clarity, Cut, and Carat. Each of these aspects affects the beauty and value of a diamond.
Color
The color of a diamond mainly refers to its “colorlessness,” which has a great impact on the diamond’s visual appeal.
Rating range: D (most colorless) to Z (distinctly yellow or brown)
Classification:
- Colorless (D~F): The most precious, with very little color, it can present a pure and transparent effect.
- Nearly colorless (G~J): The color difference is almost imperceptible to the naked eye, but the value is slightly lower.
- Slight yellow (K~M), light yellow (N~R), light yellow (S~Z): distinct color, lower price.
Effect: The closer the color is to colorless, the better the sparkle and brightness of the diamond under light refraction.
Clarity
Clarity refers to the impurities and flaws inside or on the surface of a diamond, known as “inclusions” or “surface defects”.
Rating range and levels:
- FL : Flawless, without any inclusions or surface defects.
- IF: Internally flawless, with only very minor traces on the surface.
- VVS (Very Very Slightly Included): Extremely small inclusions that can only be seen with a 10x magnifying glass.
- VS（Very Slightly Included）：Minor inclusions, visible under a magnifying glass.
- SI（Slightly Included）：Small inclusions are visible.
- I（Included）：Obvious inclusions affect transparency and brightness.
Impact: The fewer inclusions a diamond has, the rarer and more valuable it is.
Cut
Cut is the only 4C that is determined by humans, and it determines how a diamond refracts light, making it a core factor in a diamond’s beauty.
Grades: Excellent (EX), Very Good (VG), Good (G), Fair (F), Poor (P).
Evaluation criteria:
- Proportion: Whether the angles of the diamond’s facets are reasonable.
- Symmetry: Whether the cross-sections are precisely aligned.
- Definition: The final polishing process on the surface of a diamond, which affects its brightness.
- Grades: EX, VG, G, F, P.
- Note: Polishing grades EX, VG, and G are almost indistinguishable to the naked eye; usually, a grade of G or higher is sufficient to maintain a perfect appearance.
- Recommendation: If your budget allows, choose the EX version to ensure maximum brightness.
- Polish: Whether the surface is smooth and fine.
- Definition: Whether the facets of a diamond are precisely aligned.
- Grades: EX, VG, G, F, P.
- Impact: If the facets are asymmetrical (such as the table being off-center or multiple facets being deformed), it will reduce light refraction and the value of the diamond.
Impact: Well-cut diamonds maximize light refraction and shimmer, resulting in the most dazzling visual effect.
Additional information: Polish and symmetry are sub-categories of cut. Although their impact on price is not as significant as that of color and clarity, they are crucial to the visual appeal of a diamond, especially in high-quality diamonds where the differences are more pronounced.
Carat
Carat refers to the weight of a diamond; 1 carat = 0.2 grams.
Impact on value: The greater the weight, the higher the price, but other 3C conditions must also be considered.
Note: Large carat size does not equal high quality; a diamond’s brilliance, color, and clarity remain the core factors determining its value.
Why are the 4Cs no longer applicable to lab-grown diamonds?
GIA points out that the logic of the 4Cs system is based on the natural rarity of natural diamonds, which is “difficult to replicate.” However, lab-grown diamonds are born in a controlled environment, and their color and clarity can be reproduced in large quantities.
GIA research data shows that over 95% of lab-grown diamonds on the market have color and clarity within a very narrow range (D–H color, VVS–VS clarity), rendering the traditional continuous grading system meaningless. Therefore, starting in 2025, GIA decided to grade lab-grown diamonds independently, adopting a more descriptive and hierarchical dual system to reflect their actual quality differences and market value.
GIA’s new lab-grown diamond system debuts.
According to a Rapaport report on August 27, 2025, the GIA will officially implement a new grading system for lab-grown diamonds starting October 1, 2025, dividing them into two main grades:
Premium level (high standard certification)
Awarded only to a very limited number of top-quality lab-grown diamonds, under the following conditions:
- Color: D (most colorless).
- Clarity: VVS or above.
- Cut: Round drills must be of Excellent quality.
- Polish & Symmetry: Both must be Excellent.
Since less than 5% of lab-grown diamonds meet these criteria, having Premium certification signifies “top-tier rarity” and “quality assurance.”
Standard level (standard certification)
Lab-grown diamonds that meet the general high-quality market demand:
- Color: E–J.
- Clarity: VS.
- Polish: Very Good or better.
- Symmetry: Round diamonds require Very Good, fancy cuts require Good.
GIA will no longer issue grading certificates for products whose quality falls below the above standards.
The value and significance of the new system
This system is not just a change in naming, but a reshaping of the evaluation logic. Through the “Premium/Standard” two-tier structure, the GIA has established a market position for lab-grown diamonds that is independent of natural diamonds.
Redefining scarcity: Lab-grown diamonds that pass the Premium standard are extremely rare.
Enhanced value retention: Premium certification has become a symbol of quality and value.
Market transparency: Consumers can more clearly identify different quality levels.
Institutionalized differentiation: Natural and lab-grown diamonds are now officially being evaluated on a dual-track system to avoid market confusion.
Conclusion
This move by GIA symbolizes a major turning point in the global diamond industry—moving from a shared grading logic to a new era of segmented management.
As lab-grown diamond technology continues to evolve and gain wider acceptance, the establishment of Premium and Standard systems provides the market with a better basis for differentiating quality, thus re-establishing the value of lab-grown diamonds.
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