Diamond 4C Standards: International Standard Quality Assessment from GIA
Key Takeaways
- To evaluate diamond quality, experts use the diamond 4C standards of the Gemological Institute of America (GIA). Join Jemmia to learn more deeply about the 4 diamond quality evaluation standards from GIA...
To evaluate diamond quality, experts use the diamond 4C standards of the Gemological Institute of America (GIA). Join Jemmia to learn more deeply about the 4 diamond quality evaluation standards from GIA through the article below.
What are the diamond 4C standards?
Including:
- Carat (Weight): Measures the weight of the diamond.
- Cut: Evaluates the cutting technique and proportions that help the diamond reflect light best.
- Color: Evaluates the level of colorlessness of a white diamond.
- Clarity: Determines the level of inclusions and scratches inside or on the surface of the stone.
Besides the 4C standards, the beauty and overall quality of a diamond are also affected by other factors such as: fluorescence, certification papers, and other optical characteristics.
Today, the 4C standards have become the international benchmark in the diamond industry. As a brand with many years of experience in the diamond field, Jemmia will share in detail the 4 criteria for evaluating a diamond below so that you can correctly determine the value of a diamond when buying and selling:
CARAT – Diamond weight
Carat (ct) is the unit used to measure the weight of a diamond. This unit is established and standardized globally, with the exact conversion value:
1 carat = 0.2 gram = 200 milligrams = 6.5 MM
Carat is further divided into 100 points. For example: a 0.50 carat diamond is also called 50 points.
This makes measurement precise and easier to compare between diamonds.
This measurement system originates from modern gemology and has been widely popularized by reputable grading organizations such as the Gemological Institute of America (GIA) - which plays a central role in establishing global standards for the jewelry industry.
Carat weight rounding rules (according to GIA standards):
0.973 ct → rounded to 0.97 ct
0.977 ct → still rounded to 0.97 ct
0.979 ct → rounded to 0.98 ct
Weight rounding is carried out according to strict principles to ensure consistency in diamond evaluation and price listing, especially in standard price references such as the Rapaport Price List.
To ensure absolute accuracy, carat weight is measured using specialized electronic scales in the lab, with precision up to 0.0001 ct. This is an essential part of the grading process at reputable centers such as GIA, IGI, or HRD.
Carat is not just a weight figure, but also one of the most important measures of a diamond’s value. Generally, the greater the diamond’s weight, the higher its value. However, a highly valuable diamond does not depend only on Carat, but also on the other 4Cs factors such as Cut - Color - Clarity. Let’s continue with Jemmia to learn about the next criterion, Color.
See more: Measurement Unit What Is Carat? The Difference Between Carat and Kara
Diamond weight is also called Carat
COLOR – Diamond color (Diamond color grade)
During the formation process, diamonds can have many different colors. The color most commonly crafted into jewelry is pure white diamond.
The most widely used diamond color grading system today was developed in the 1950s by scientist Richard T. Liddicoat at the Gemological Institute of America (GIA).
GIA uses the Latin alphabet starting from “D – Z” to distinguish diamond color in detail, called the “D – Z” Color Scale. The highest color grade is D. The purer the color, the higher the diamond’s value. Diamond color grades are divided into the following levels:
- D, E, F (Colorless): Colorless, transparent diamonds with the highest value. D is the most perfect and expensive color grade.
- G, H, I, J (Near Colorless): Diamonds that are nearly colorless or have no obvious color.
- K, L, M (Faint Yellow): Diamonds with a slight color, usually light yellow or light brown.
- N,O, P, Q, R (Very Light Yellow): Diamonds with visible yellow or brown color in many areas.
- S – Z (Light Yellow): Diamonds that clearly show yellow or brown color and are very easy to recognize.
Diamond color grades range from D to Z
See more: Diamond color grade what is it? Standard scale from GIA
In addition, natural diamonds also come in other colors such as red, blue, black, pink, ... Some vividly colored diamonds may be worth more than a D-color diamond.
CLARITY – Diamond clarity
Clarity is the criterion used to evaluate the level of structural perfection of a diamond, based on the number, size, position, and visibility of internal inclusions and external blemishes.
The clarity of a diamond is affected by 4 main factors:
- Size of the inclusions
- Number of inclusions
- Visibility – how easy they are to see
- Position of the inclusions in the diamond
When evaluating Clarity, experts observe the diamond under a 10x magnifying loupe according to GIA (Gemological Institute of America) standards to provide accurate and objective results.
Diamond clarity is divided into 6 groups with 11 grades, specifically:
- Flawless (FL): No inclusions or blemishes visible under 10x magnification.
- Internally Flawless (IF): No internal inclusions; only very small surface blemishes may be present.
- Very, Very Slightly Included (VVS1, VVS2): Extremely tiny inclusions, very difficult to detect under 10x magnification.
- Very Slightly Included (VS1, VS2): Small inclusions that may be difficult or relatively easy to see under 10x magnification.
- Slightly Included (SI1, SI2): Inclusions visible under 10x magnification, but usually difficult to see with the naked eye.
- Included (I1, I2, I3): Obvious inclusions that affect the transparency and light reflection ability of the diamond.
Diamond clarity is graded from FL to I3
There are many different types of imperfections in diamonds, divided into two types: flaws that do not affect structure and flaws that do affect structure.
Flaws that do not significantly affect structure and are acceptable:
- Pinpoint: Very small dot or point
- Feather: Feather-like mark
- Crystal: Crystal
- Cloud: Cloudy haze
- Needle: Needle-like mark
Flaws that affect structure:
- Natural: Indentation
- Chip: Chipped mark
- Clavity: Cavity
- Twinning wisp: Many internal strain marks
- Bearding: Bearded girdle
Flaws that affect the value of a diamond
High 4Cs diamond standards at Jemmia Diamond:
CUT – Diamond cut (Diamond craftsmanship quality)
Cut is one of the most important criteria in the 4C standards, used to determine the value and beauty of a diamond. Cut directly affects the diamond’s brilliance, sparkle, and overall shape.
Unlike weight or color, cut reflects craftsmanship, determining how the diamond reflects and refracts light to create its signature radiant effect.
A diamond cut is made up of 7 main components as follows:
- Table: The top surface of the diamond and the largest facet that comes into contact with light.
- Crown: The part extending from the top surface (Table) to the girdle. The Crown is the widest part of the diamond.
- Girdle: The outline around the diamond and the intersection between the Pavilion and Crown. This part is used to determine the circumference of the diamond.
- Diameter: Shows the measurement from one edge of the diamond straight across to the opposite side.
- Pavilion: The part extending from the Girdle toward the Culet and the bottom portion of the diamond.
- Culet: The smallest facet of the diamond and parallel to the Table.
- Depth: The depth of the diamond, the distance from the Table to the Culet.
Structure of 58 facets in a Round Brilliant Cut diamond (GIA Standard):
7 components that make up a diamond cut
A diamond’s cut is evaluated based on three factors: Proportions, symmetry, and polish. Each factor affects the diamond’s overall beauty and produces different levels of light reflection. Diamond cut is classified as follows, with Excellent being the most perfect cut:
- Excellent (Excellent)
- Very Good (Very good)
- Good (Good)
- Fair (Average)
- Poor (Poor)
Diamond cut classification
Besides cut quality, there are currently many popular diamond cuts for you to choose from. You can choose a cut based on personal preference to get the diamond that suits you best.
Some common shapes include: Round, Asscher (Square), Princess (Princess diamond), Emerald (Rectangle), and Heart, Marquise, Pear, Oval.
Popular diamond cut shapes
Other factors affecting a diamond’s value
In addition to the 4Cs factors above, a diamond’s value is also affected by fluorescence. Fluorescence is the phenomenon in which a diamond glows when exposed to ultraviolet (UV) light. GIA states that about 35% of diamonds have this phenomenon, most commonly blue light, in addition to white, yellow, or orange.
Diamonds with strong blue fluorescence may reduce yellow tint under sunlight, but if the fluorescence is too strong, the diamond will look hazy and lose value. Diamond fluorescence intensity is divided into the following grades:
- None (No fluorescence)
- Faint (Weak)
- Medium (Medium)
- Strong (Strong)
- Very Strong (Very strong)
The higher the fluorescence, the lower the diamond’s value
Which factor is most important in evaluating a diamond?
Each criterion in the diamond 4C standards plays an important role in determining the value of a diamond. However, cut quality (CUT) is often considered more important because it directly affects the diamond’s appearance and light reflection ability. To make the most accurate assessment of value, it is necessary to fully combine all four factors of the 4C standards.
Jemmia’s High GIA Standard 4Cs Diamond Quality
Every diamond at Jemmia undergoes a strict selection process according to international 4Cs standards, directly certified by GIA (Gemological Institute of America) - the world’s leading reputable diamond grading organization.
Jemmia believes that diamonds are not only jewelry, but also symbols of true value and class. Therefore, we only accept 2% of diamonds with the most outstanding beauty and quality, in order to ensure long-term and sustainable asset value for customers.
Discover the premium GIA natural diamond selection standards at Jemmia:
Color: Jemmia only selects diamonds with colors from D to I (D, E, F, G, H, I), ensuring the highest level of whiteness and purity on the diamond color grading scale.
Clarity: Jemmia carefully selects diamonds with clarity from FL (Flawless) to VS2 (Very Slightly Included), including FL, IF, VVS1, VVS2, VS1, and VS2 grades. These diamonds are almost free of blemishes or have only very small blemishes that are difficult to notice, ensuring high brilliance and perfection.
Cut: At Jemmia, all diamonds are cut to the Triple Excellent Cut standard, ensuring:
- Perfect cut
- Perfect symmetry
- Perfect polish
📞 Contact now at 0838 353 333 or Zalo Jemmia Diamond to receive advice from diamond experts on a diamond suitable for your needs and budget.
Jemmia Diamond is proud to be a partner certified by the Gemological Institute of America (GIA) in three aspects:
- Official distributor
- Unit trained and standardized by GIA in expert knowledge
- Unit classified and evaluated by GIA for diamonds
At Jemmia, every diamond, whether small or large, is carefully inspected before reaching the customer. This process uses modern equipment imported from GIA, ensuring each diamond achieves the highest quality and brings absolute peace of mind.
Jemmia owns a GIA-standard laboratory equipped with advanced devices such as:
- GIA ID 100 tester
- GIA Match iD girdle inscription viewer
- GIA Gemolite® NXT Professional Edition gem microscope
- GIA Diamond Dock
With a strict equipment system and rigorous procedures, Jemmia ensures that every diamond delivered to customers is perfect, bringing absolute satisfaction.
See more:
- What Is a Diamond? A Complete Summary of Diamond Knowledge
- Diamond Certification Papers: Types and How to Read Them
- Long-Term Diamond Investment: How Profitable Is It?
The diamond 4C standards have been shared in detail by Jemmia in the article above. If you have any questions about how to determine the value of a diamond, please leave a comment below so our experts can answer for you. Follow Jemmia to learn more about diamonds.
