This comprehensive guide will introduce you to the crucial elements of diamond grading, with a focus on round diamonds, the most popular and versatile shape. By the end of this article, you will be equipped with the knowledge to confidently navigate the diamond market.
Table of Contents
Diamonds have captivated human fascination for centuries, symbolizing wealth, power, and timeless beauty. Known for their brilliance and durability, diamonds are often associated with significant life events, such as engagements, weddings, and anniversaries, making them one of the most sought-after gemstones in the world. However, selecting the perfect diamond involves more than just choosing the largest stone or the most dazzling display. To truly appreciate a diamond’s value and ensure you are making a well-informed purchase, it is essential to understand the factors that define its quality.
1. The 4Cs of Diamonds
The quality and value of a diamond are assessed based on four fundamental criteria known as the 4Cs: Cut, Color, Clarity, and Carat Weight. These criteria were established by the Gemological Institute of America (GIA) and are now the universal standard for evaluating diamonds.
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- Cut: The cut of a diamond refers to how well it has been shaped and faceted. This is arguably the most important of the 4Cs because it directly affects the diamond’s brilliance. A well-cut diamond will reflect light in a way that maximizes its sparkle, while a poorly cut diamond will appear dull and lifeless. The cut grade ranges from Excellent to Poor, with each level indicating how precisely the diamond has been crafted to optimize light performance.
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- Color: Diamond color grading assesses the absence of color in a diamond. The less color present, the higher the grade, with D being completely colorless and Z having noticeable yellow or brown hues. While colorless diamonds are the most highly valued, near-colorless diamonds can also appear stunning, especially when set in yellow or rose gold, which can mask slight color tints.
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- Clarity: Clarity refers to the presence of internal flaws (inclusions) and external imperfections (blemishes) within a diamond. The clarity grade ranges from Flawless (FL), with no inclusions or blemishes visible under 10x magnification, to Included (I1, I2, I3), where imperfections are visible to the naked eye. High clarity diamonds are rarer and more valuable, but many inclusions are microscopic and do not significantly affect the diamond’s beauty to the naked eye.
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- Carat Weight: Carat weight measures the size of a diamond, with one carat equaling 200 milligrams. Larger diamonds are rarer and therefore more expensive. However, carat weight alone does not determine a diamond’s value; a smaller diamond with excellent cut, color, and clarity can be more valuable than a larger diamond with lower grades in these categories.
Understanding the 4Cs is essential for anyone looking to purchase a diamond, as these factors collectively determine the stone’s overall quality and value. Balancing these aspects based on your budget and preferences will help you find the perfect diamond that suits your needs.
2. Round Diamonds and the Importance of Cut
Round diamonds are the most popular and widely recognized diamond shape, accounting for nearly 75% of all diamonds sold. This shape is beloved for its timeless appeal and its ability to maximize a diamond’s brilliance. The round cut, with its 58 facets, is designed to reflect light in a way that enhances the diamond’s natural sparkle and fire. The brilliance of a round diamond is primarily determined by its cut, which refers to how well the diamond’s facets interact with light.
The cut of a diamond is evaluated based on three main aspects: polish, symmetry, and proportions. Polish refers to the surface smoothness of the diamond, which affects how light passes through the stone. Symmetry assesses the precision and alignment of the diamond’s facets. Both polish and symmetry are graded on a scale from Excellent to Poor, with higher grades indicating better craftsmanship.
3. Cut Grading
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- Excellent: This grade is awarded to diamonds that have been cut to optimal proportions and symmetry. An Excellent cut ensures that almost all the light entering the diamond is reflected back through the top, creating maximum brilliance and fire. Diamonds with an Excellent cut are highly sought after and represent the pinnacle of diamond cutting craftsmanship.
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- Very Good: Diamonds with a Very Good cut reflect most of the light that enters them, offering high levels of brilliance and sparkle. Although not as perfectly proportioned as an Excellent cut, these diamonds are still of very high quality and often offer a balance between beauty and cost.
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- Good: A Good cut diamond reflects a substantial portion of the light that enters it, but some light may escape through the sides or bottom. These diamonds are often chosen for their lower price point while still providing a decent level of brilliance.
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- Fair: Fair cut diamonds allow a significant amount of light to escape, resulting in reduced brilliance and sparkle. These diamonds are less desirable in terms of visual appeal but may be an option when budget constraints are a primary concern.
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- Poor: Poor cut diamonds have proportions that cause most of the light to leak out of the sides or bottom, leading to a dull appearance with minimal sparkle. These diamonds are generally not recommended unless size or budget is the only consideration.
The cut grade significantly influences a diamond’s overall appearance and value. Even a diamond with high color and clarity grades can appear dull if it has a Poor cut. Therefore, prioritizing cut quality is essential for ensuring the diamond’s beauty.
Diamond Cut Chart
4. Understanding Clarity
Clarity is one of the 4Cs that significantly affects a diamond’s appearance and value. Clarity refers to the presence of internal characteristics, called inclusions, and surface irregularities, known as blemishes. These imperfections are natural and occur during the diamond’s formation under intense heat and pressure deep within the Earth.
The GIA clarity scale ranges from Flawless (FL), with no inclusions or blemishes visible under 10x magnification, to Included (I1, I2, I3), where inclusions are visible to the naked eye and may affect the diamond’s brilliance.
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- Flawless (FL): These diamonds have no inclusions or blemishes visible under 10x magnification. They are extremely rare and command the highest prices.
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- Internally Flawless (IF): IF diamonds have no inclusions but may have minor blemishes visible under 10x magnification. These diamonds are also rare and highly valued.
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- Very, Very Slightly Included (VVS1 and VVS2): Diamonds in this category have minute inclusions that are extremely difficult to see even under 10x magnification. VVS diamonds are highly prized for their near-perfect clarity.
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- Very Slightly Included (VS1 and VS2): These diamonds have minor inclusions that are visible under 10x magnification but are not noticeable to the naked eye. VS diamonds offer a great balance between clarity and value.
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- Slightly Included (SI1 and SI2): SI diamonds have inclusions that are visible under 10x magnification and may sometimes be visible to the naked eye. However, many SI diamonds are eye-clean, meaning their inclusions are not noticeable without magnification.
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- Included (I1, I2, I3): Diamonds in this category have inclusions that are clearly visible to the naked eye and may affect the diamond’s transparency and brilliance. These diamonds are the most affordable but may lack the visual appeal of higher clarity grades.
Most diamonds contain some form of inclusion or blemish, but the impact on the diamond’s appearance varies. Many inclusions are microscopic and do not affect the beauty or durability of the diamond. However, larger or more prominent inclusions can interfere with the way light passes through the diamond, reducing its brilliance. Choosing the right clarity grade depends on your preferences and budget. While higher clarity grades are more expensive, many people find that diamonds with lower clarity grades offer an excellent balance of beauty and value, especially when inclusions are not easily visible without magnification.
5. Color Grading in Detail
Diamond color grading is a critical factor in determining a diamond’s value and overall appearance. The color grading scale established by the GIA ranges from D (colorless) to Z (light yellow or brown).
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- D-F (Colorless): Diamonds in this range are considered completely colorless, with D being the highest grade. These diamonds are the rarest and most valuable. Colorless diamonds allow the most light to pass through, resulting in exceptional brilliance and fire.
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- G-J (Near Colorless): Diamonds in this range have a slight hint of color that is usually only noticeable when compared to higher color grades. However, they offer an excellent value, as the color is typically not discernible to the untrained eye, especially once the diamond is set in jewelry.
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- K-M (Faint Color): These diamonds have a noticeable warm tint, usually yellow or brown. While they are less valuable than higher color grades, they can still be attractive, particularly in certain settings, such as yellow gold, which complements the diamond’s natural color.
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- N-Z (Noticeable Color): Diamonds in this range have a visible color that is apparent even to the naked eye. They are the most affordable but are often less desirable for those seeking a classic, colorless diamond appearance.
Beyond the traditional color grading scale, diamonds can also come in “fancy” colors, such as yellow, pink, blue, and green. These fancy colored diamonds are graded on a different scale, focusing on the intensity of the color rather than the absence of it. For yellow diamonds, once the color grade goes beyond Z, they are classified as Fancy Yellow, and these stones can range from light to vivid. Fancy colored diamonds are rare and often more expensive than colorless diamonds, especially in intense shades. The market for fancy colored diamonds is niche but growing, with collectors and investors alike drawn to their unique hues and rarity.
Color preference is subjective, and the best color for your diamond will depend on your personal taste and how you plan to set the stone. For example, near-colorless diamonds (G-J) can appear just as stunning as colorless diamonds when set in white gold or platinum, offering an excellent balance between beauty and cost. On the other hand, diamonds with a faint color (K-M) may be more appealing when set in yellow or rose gold, where the metal’s warmth can mask the diamond’s natural hue.
6. Carat Weight and Its Implications
Carat weight is often the first thing people consider when choosing a diamond, as it directly relates to the size of the stone. One carat equals 200 milligrams, and diamonds are measured to the hundredth decimal place. Larger diamonds are rarer and therefore command a higher price, but it’s essential to remember that carat weight alone doesn’t determine a diamond’s beauty. Other factors, such as cut, color, and clarity, play significant roles in a diamond’s overall appeal and value.
The perceived size of a diamond also depends on its cut, shape, and proportions. For example, a well-cut diamond can appear larger and more brilliant than a poorly cut diamond of the same carat weight. Additionally, round diamonds tend to look smaller than fancy shapes like oval, pear, or marquise, which can have larger surface areas for the same carat weight.
To help buyers understand the relationship between carat weight and size, here is a general guide to diamond diameter in millimeters:
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- 0.1 carat: approximately 3.0 mm in diameter
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- 0.5 carat: approximately 5.1 mm in diameter
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- 1.0 carat: approximately 6.5 mm in diameter
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- 2.0 carats: approximately 8.2 mm in diameter
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- 3.0 carats: approximately 9.3 mm in diameter
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- 4.0 carats: approximately 10.2 mm in diameter
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- 5.0 carats: approximately 11.0 mm in diameter
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- 6.0 carats: approximately 11.7 mm in diameter
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- 7.0 carats: approximately 12.3 mm in diameter
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- 8.0 carats: approximately 12.8 mm in diameter
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- 9.0 carats: approximately 13.3 mm in diameter
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- 10.0 carats: approximately 14.0 mm in diameter
Understanding how carat weight affects both the size and price of a diamond is crucial for making an informed purchase. It’s also important to note that diamond prices do not increase linearly with carat weight. For example, a 2-carat diamond may cost significantly more than twice the price of a 1-carat diamond, especially if it also has higher grades in cut, color, and clarity.
When choosing a carat weight, consider the wearer’s lifestyle and personal preference. Larger diamonds are more noticeable and may be more prone to damage during everyday activities, while smaller diamonds offer a subtler, more versatile look. Ultimately, the best carat weight is one that fits your budget, complements the wearer’s style, and meets your expectations for size and impact.
7. Key Proportions in Diamond Cutting
The proportions of a diamond are essential in determining how well it reflects light, which directly affects its brilliance and fire. Two critical aspects of diamond proportions are table size and depth. The table is the largest facet of a diamond, located on the top surface, while the depth is the distance from the table to the culet (the pointed bottom of the diamond).
An ideal table size for a round diamond is typically between 54% and 57% of the diamond’s overall diameter. The table plays a crucial role in how light enters the diamond and reflects back out, contributing to the stone’s overall brilliance. If the table is too large, it can cause light to leak out of the sides of the diamond, reducing its sparkle and giving it a flat appearance. Conversely, a small table can make the diamond look darker or less lively, as it may not capture and reflect light as effectively.
Depth percentage, which ideally falls between 59% and 62.5% for round diamonds, is another crucial factor. Depth refers to the height of the diamond from the culet to the table, measured as a percentage of the diamond’s diameter. If the depth is too shallow, light will escape through the bottom of the diamond, resulting in a “fisheye” effect, where the diamond appears dull and lacks brilliance. If the depth is too deep, light may be absorbed within the diamond or leak out of the sides, creating a “nailhead” effect where the center of the diamond appears dark.
Symmetry is also a key factor in diamond cutting, referring to the precision of the diamond’s shape and the alignment of its facets. Poor symmetry can cause light to be misdirected or lost within the diamond, reducing its overall brilliance. For example, if the facets are not properly aligned, light may leak out through the bottom or sides of the diamond, diminishing its sparkle. High symmetry grades (Excellent or Very Good) indicate that the diamond has been cut with great precision, ensuring that light is effectively reflected and refracted to create maximum brilliance.
Polish is another aspect of cut quality, indicating the smoothness of the diamond’s surface. A diamond with Excellent or Very Good polish will have a smooth, reflective surface that enhances its brilliance. Poor polish, on the other hand, can create tiny scratches or marks on the diamond’s surface, disrupting the way light interacts with the stone and reducing its overall sparkle.
When evaluating a diamond’s cut, it’s important to consider all these factors—table size, depth, symmetry, and polish—together. A well-cut diamond with ideal proportions will maximize light performance, resulting in a stunning, brilliant stone that captures the eye.
Source: Image above is from the GIA's educational materials
8. Fluorescence in Diamonds
Fluorescence is a natural phenomenon that occurs in some diamonds when they are exposed to ultraviolet (UV) light. Approximately 25-35% of diamonds exhibit some degree of fluorescence, which typically manifests as a blue glow, although it can also appear in other colors like yellow, green, or orange. The GIA grades fluorescence on a scale from None to Very Strong, and its impact on a diamond’s appearance can vary depending on the stone’s color grade and the strength of the fluorescence.
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- None: Diamonds with no fluorescence will not exhibit any glow under UV light. These diamonds are highly valued by those who prefer a more predictable and consistent appearance under all lighting conditions.
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- Faint: Diamonds with faint fluorescence exhibit a very slight glow under UV light, which is usually not noticeable under normal lighting conditions. These diamonds are often indistinguishable from non-fluorescent diamonds to the naked eye and can sometimes be found at a slightly lower price.
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- Medium: Medium fluorescence can sometimes be seen under strong UV light but rarely affects the diamond’s appearance in normal lighting. In some cases, medium fluorescence can enhance the appearance of diamonds with lower color grades, making them appear whiter.
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- Strong and Very Strong: Diamonds with strong or very strong fluorescence can show a noticeable glow under UV light, which can sometimes affect their appearance. In rare cases, strong fluorescence can cause the diamond to appear slightly hazy or oily under natural light. However, for many people, this effect is minimal and does not detract from the diamond’s beauty.
The impact of fluorescence on a diamond’s value is a subject of debate among gemologists and buyers. Some people prefer diamonds with a slight fluorescence because it can enhance their visual appeal under certain lighting conditions, while others may avoid it due to the potential for a hazy appearance. It’s important to view diamonds with varying levels of fluorescence under different lighting conditions to determine if this characteristic affects your preference.
For diamonds with higher color grades (D-F), fluorescence may have a more noticeable impact, as these diamonds are prized for their colorlessness and any blue fluorescence could alter their appearance. However, for diamonds with lower color grades (G and below), fluorescence can sometimes enhance their appearance, making them look whiter and more vibrant.
When purchasing a diamond, it’s advisable to consider fluorescence as one of many factors and to view the diamond under various lighting conditions before making a decision. For some buyers, fluorescence adds a unique characteristic to the diamond, while for others, it might be an aspect to avoid depending on their preferences.
Read our detailed article on fluorescence in colorless and colored diamonds
9. International Certification Laboratories
When purchasing a diamond, obtaining a certificate from a reputable laboratory is crucial to verify the diamond’s quality and authenticity. The three most recognized international certification laboratories are the Gemological Institute of America (GIA), the International Gemological Institute (IGI), and the Hoge Raad voor Diamant (HRD).
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- GIA (Gemological Institute of America): GIA is widely considered the most reliable and stringent diamond grading authority. A GIA certificate provides an accurate assessment of the diamond’s 4Cs and other important characteristics. This certification is highly respected and often increases the resale value of the diamond. GIA is known for its consistency and strict grading standards, making it a preferred choice for consumers and jewelers alike.
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- IGI (International Gemological Institute): IGI is another reputable laboratory, known for its thorough grading and certification processes. IGI certificates are common in retail jewelry and are recognized globally. While sometimes seen as slightly more lenient than GIA, IGI certification still offers buyers confidence in their purchase. IGI is also popular for grading diamonds that are set in jewelry, making it a practical choice for those purchasing finished pieces rather than loose diamonds.
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- HRD (Hoge Raad voor Diamant): Based in Antwerp, Belgium, HRD is a prestigious laboratory particularly well-known in Europe. HRD certification ensures that the diamond has been thoroughly evaluated and meets strict quality standards. HRD certificates are trusted by professionals in the diamond industry and provide detailed information on the diamond’s characteristics. HRD is known for its detailed reports, which include a clear and precise description of the diamond’s 4Cs as well as other important aspects.
Each of these laboratories provides a detailed grading report that offers insight into the diamond’s qualities, allowing buyers to understand exactly what they are purchasing. The certificates typically include information on the diamond’s 4Cs, fluorescence, and other important characteristics, such as the measurements, proportions, and any inscriptions.
When purchasing a diamond, it is essential to choose one that comes with a certification from a reputable lab. This certification acts as a guarantee of the diamond’s quality and authenticity, giving buyers peace of mind and ensuring that they are making an informed investment. It is also a useful tool for insurance purposes and can be important if the diamond is ever resold.