Diamond Certification, Best Grading Labs Ranked

• A diamond's certification or grading carries immense significance. It's imperative to buy a diamond with an accompanying grading report from a reputable lab. Beware of local jewelers attempting to dissuade the necessity of a grading report; their intention is often to sway you towards an ungraded diamond. Such a tactic could result in the sale of a diamond with a lower grade, thereby yielding substantially higher profits.
• Respected diamond dealers frequently opt to send their stones to AGS or GIA for grading due to their commitment to consistency and transparency. AGS and GIA are known for their stringent and professional approach to diamond grading.
• AGS, an esteemed grading lab, is enhancing its accuracy in grading clarity, particularly in lower grades like SI2 diamonds. Notably, AGS excels in assessing a diamond's cut grade, employing a proportion-based system.
• Buyers should prepared to evaluate the cut grade within a GIA grading report. It's worth noting that GIA provides a cut grade exclusively for round diamonds. In the case of round diamonds, our guidelines on ideal proportions for each shape play a pivotal role in distinguishing between a super ideal cut and a GIA graded diamond with an average excellent cut.
• IGI stands as a decent lab, though not on par with AGS or GIA. For diamonds with lower color grades (I-J-K), IGI suffices. However, if your aim is to acquire a premium-grade diamond, adhering to AGS or GIA is advisable.
• GCAL, a reputable lab, though holding a smaller market share, aligns with the standards of AGS and GIA. Thus, if you encounter a GCAL graded diamond, there's no hesitation required in making a purchase. Frequently, a GCAL diamond is accompanied by a GIA report.
• Conflicting viewpoints on diamond labs are prevalent due to dealers tailoring their opinions to favor labs that have graded their diamonds. To make a well-informed choice, delve into our comprehensive diamond guide tailored for each shape.

In summary, for reliable diamond grading, the top recommendations are AGS and GIA, which are widely regarded as trustworthy and consistent. HRD and GCAL are also considered reliable labs. The International Gemological Institute (IGI) has been making improvements in its diamond grading process. However, the European Gemological Laboratory (EGL) has faced a loss of credibility and market share due to inconsistencies. The Gemological Science International (GSI) is generally satisfactory, though occasional grade inconsistencies may arise. The Professional Gem Science Laboratory (PGS) is dependable but less known in the market.

AGSL - AGS Certification

The American Gem Society (AGS) functions as a membership organization encompassing jewelers, suppliers, appraisers, and traders. Its inception dates back to 1934. However, its laboratories, known as the American Gem Society Laboratories (AGSL), were established in 1996. The organization also features an advanced instruments division, founded in 2004. AGSL is primarily responsible for grading diamonds and has developed its own set of standards. It stands as a formidable rival to the GIA and holds a strong reputation within the diamond industry.

Yet, an area of concern arises when AGS grades the clarity of diamonds, particularly in the SI1/SI2 range. Instances have been observed where AGS graded diamonds in the SI2 category as if they were more akin to I1 diamonds. Consequently, caution is advised when dealing with AGS's inconsistencies in grading clarity within the SI2 range.

Please note AGS merged with GIA in late 2022. As such, these insights are relevant to existing AGS grading reports. 

GIA Certification

The Gemological Institute of America (GIA) operates as a non-profit organization focused on the research and education of consumers regarding jewelry and gemstones. Their involvement encompasses the study and grading of diverse gemstones. Alongside their lab services, GIA offers training for gemologists and provides comprehensive education and research support to the diamond industry. GIA's diamond grading reports are highly esteemed as the foremost "certifications" and verification documents in the industry.

GIA offers two distinct types of diamond grading reports: full reports and diamond dossiers designed for smaller diamonds. Dossiers are more cost-effective compared to full reports, yet they lack the complete plot of a diamond, omitting the precise location of inclusions. In the case of dossiers, GIA mandates a laser inscription on the diamond, given the absence of inclusion locations. Conversely, full reports offer a different approach. Diamond dealers have the option to include a laser inscription as an additional service within full reports, for an added fee of $30.

However, with GIA's expansion, concerns have arisen regarding the declining quality of their grading services. Instances have emerged where GIA categorized a G-color-graded diamond as a lower H color.

Discussions also revolve around GIA's methodology for determining excellent cuts in diamonds. A point of contention pertains to the broad criteria employed when assigning excellent cut grades to diamonds – the highest tier on GIA's scale. In comparison, it has been suggested that AGS's utilization of a proportion-based system for assigning ideal cut grades in their reports may yield a superior grading approach. For those considering well-cut GIA graded diamonds, it's advisable to delve into diamond proportions and refer to a chart.

HRD Certification

HRD Antwerp, closely linked to the Antwerp World Diamond Center, occupies a significant role within the diamond trading and supply sector. Established in 1973, HRD represents the Belgian diamond industry. The HRD Lab adheres to standards akin to those of GIA and follows grading regulations set by the International Diamond Council, underlining its reliability.

Nevertheless, it is worth noting the possibility of grade inconsistencies in HRD's grading process, particularly in relation to diamond color and clarity. This aspect warrants consideration when contemplating the purchase of HRD-graded diamonds.

IGI Certification

Founded in 1975 and headquartered in Antwerp, the International Gemological Institute (IGI) has a global presence with multiple branches and a gemology school. However, IGI's widespread reach translates to slightly varying grading criteria among their labs in different countries. While still a major player, IGI's accuracy is generally considered somewhat lower compared to GIA or AGS. Anticipating one-grade inconsistencies when purchasing IGI-graded diamonds is common. Recognizing the uniqueness of each diamond, a generalized approach is less effective as individual cases require tailored consideration.

As such, a degree of grading inconsistency across all 4Cs is to be expected when it comes to IGI's grading.

GSI Certification

Gemological Science International (GSI) primarily serves to grade diamonds for large chain stores, with a focus on high-volume grading. With a global expansion, GSI's appeal to large stores lies in their ability to expedite diamond grading compared to GIA or AGS. While their accuracy is comparable to IGI in diamond grading, GSI often assigns slightly lower grades compared to GIA or AGS. Nonetheless, due to the distinct characteristics of each diamond, individual evaluation remains crucial.

For those without comprehensive knowledge or the time for exhaustive research, opting for either GIA or AGS certifications is advisable.

Prudence is recommended when assessing GSI-graded diamonds, as some degree of grade inconsistency may occur. Seeking the expertise of a third-party expert can be beneficial, considering that the reliability of appraisers can vary. This may entail trade-offs when acquiring GSI-graded diamonds.

EGL Certification

The European Gemological Laboratory (EGL) once held a significant stake in the diamond grading realm. However, its credibility has suffered, resulting in a decline in reputation. EGL is currently undergoing reorganization, leading to skepticism about relying solely on their reports. Due to its diminished reputation, platforms like RapNet have chosen to exclude EGL-graded diamonds from their listings.

Given these circumstances, exercising caution when considering EGL-graded diamonds is prudent, particularly unless they are from the 1950s to the early 2000s. Even within this time frame, up to two grade inconsistencies in overall grading may be anticipated.

To make well-informed decisions regarding various diamond grading reports and certifications, it's essential to comprehend the process of diamond grading itself.

The major grading laboratories employ remarkably similar procedures for assessing and grading diamonds. The process typically involves multiple graduate gemologists independently evaluating a diamond's cut, color, clarity, and carat weight. The final grades are determined after all evaluations have been considered. This approach helps minimize the potential for human error in establishing a diamond's final grade, although it doesn't eliminate it entirely.

Inconsistencies can arise when a diamond is reevaluated by a different lab, particularly when a stricter or more consistent lab reassesses a diamond graded by a less rigorous lab. Such inconsistencies are more pronounced among labs with varying grading standards.

It's important to note that diamonds are not certified; labs avoid using the term "certifying" as it could lead to legal issues. Instead, labs confirm that they have graded a diamond based on their professional judgment, as detailed in the grading report.

Consistency in Results

One of the reasons for the dominance of AGS and GIA in the industry is their consistent and accurate grading. If you were to send a diamond to AGS or GIA for evaluation, you would likely receive very similar grading results with minimal discrepancies. Some level of slight variation is considered acceptable within the industry.

Organizational Structure Matters

AGS operates as a membership organization, while GIA is a non-profit entity. Both AGS and GIA are regarded as more objective compared to other labs when it comes to grading diamonds. This objectivity is influenced by their organizational structures, focusing on maintaining consistent and accurate grading standards.

On the other hand, some commercial labs are profit-driven and more customer-oriented toward diamond merchants. This can lead to discrepancies in grading results. In certain cases, commercial labs may assign slightly higher grades on average than AGS or GIA to satisfy their clients.

Buyer's Perspective

From a buyer's standpoint, diamond certification plays a pivotal role when purchasing a diamond. While there are several grading labs, diamonds graded by AGS or GIA are generally considered more reliable and consistent in their assessment. It's crucial to be cautious when encountering diamonds with similar grades from different labs at significantly lower prices, as the lower price might indicate lower quality.

Ultimately, when buying a diamond, especially for an engagement ring or other significant occasions, opting for a diamond graded by AGS or GIA is recommended due to their established reputation for accuracy and consistency.

Refer to our guide on lab-grown diamonds and the differences between lab-grown and natural diamonds for further insights. These resources will provide you with valuable information to guide your diamond-buying journey.

The GIA Diamond Cut Grading System

One of the most significant advancements in the diamond industry during the 1950s was the introduction of the GIA's cut grading system. This system played a pivotal role in standardizing the evaluation of diamonds, aiming for consistent judgment across the industry. While the 4Cs of diamond grading were established concepts, and various other grading systems were in use, the necessity arose for a universal grading system. Presently, GIA's 4Cs grading system stands as the most widely adopted and accepted standard for diamond grading.

The GIA system meticulously evaluates a diamond's color, clarity, and cut, which encompasses its cut, polish, and finish. Based on this evaluation, a diamond can be assigned one of five grades:

1. Excellent Grade: Diamonds achieving this grade exhibit an even distribution of light and dark areas when observed, accompanied by pronounced brilliance and scintillation.

2. Very Good Grade: Diamonds within this category also display notable brilliance and scintillation but may have slightly more darkness in the center or around the edges. Additionally, the diamond's pattern holds significance. Sometimes, despite excelling in other aspects, a diamond might have an imperfect pattern, leading to a downgrade from "excellent" to "very good."

3. Good Grade: Diamonds falling into this range tend to be darker than those in higher grades or might lack sufficient brilliance and scintillation. The diamond's pattern quality is also of lesser caliber. Another factor influencing this grade could be the diamond's weight ratio, with some stones having an unusually high weight ratio, exceeding that of an average gem of the same diameter. In such instances, the diamond might be downgraded by one step.

4. Fair Grade: Diamonds assigned this grade often lack substantial brilliance or scintillation. Dark patches might be prevalent in key areas like the table region or girdle. Poor cutting, noticeable imperfections in symmetry and proportion, and a lack of quality in the diamond's overall appearance can also result in this grade.

5. Poor Grade: Diamonds in this classification exhibit notable deficiencies. They generally possess subpar proportions and symmetry due to flawed cutting, resulting in limited brilliance and scintillation. This grade might encompass diamonds with "nail heads," characterized by a central black patch, or "fish eyes," where the center lacks brilliance. Once again, the diamond's weight ratio is a pivotal consideration.

Beyond factors such as brilliance, scintillation, symmetry, and weight ratio, the GIA diamond cut grading process also takes into account durability aspects, including thin girdles and inclusions. Furthermore, polish quality, encompassing nicks, scratches, chips, and other surface imperfections, plays a role in the assessment.

AGS Proportion-Based Cut Grade System

The AGS proportion-based cut grade system has emerged as a formidable contender to challenge the dominance of the GIA grading system within the industry. Interestingly, both AGS and GIA were initially funded by the same individual, Robert Shipley. However, differing opinions on the parameters and methodology for grading diamond cuts led to their divergence, with AGS establishing its lab and grading system.

In contrast to the comprehensive GIA system, which provides an overall designation based on multiple diamond features, the AGS proportion-based cut grade system assesses a diamond's color, clarity, and cut individually. It assigns each aspect of the diamond one of 11 levels, ranging from 0 to 10—where zero represents the best and ten the worst. A diamond receiving three 0s attains a flawless cut, featuring impeccable polish, proportions, symmetry, and optimal light performance.

Clarity Scale: As the name implies, the clarity scale gauges a diamond's clarity and the presence of inclusions. A score of 0 signifies a flawless diamond devoid of visible inclusions, embodying impeccable clarity. Levels 1 and 2 fall under the "very slightly included" category, while 3 and 4 are labeled "very slightly included." The scale progresses to levels 5 and 6, indicating noticeable but slight inclusions. Levels 7 to 10 signify substantial inclusions, with 10 being the most included.

Color Scale: Reflecting its name, the color scale assesses the diamond's color. A score of 0 to 1.0 signifies a completely colorless diamond, conforming to the industry's ideal color standard. Levels 1.5 to 3.0 are designated as "near colorless," while 3.5 to 5.0 denote faint colorations slightly perceptible to the naked eye. Levels 5.0 to 7.0 reflect "very light" colorations, progressing to 7.5 to 10.0, characterized by light but more noticeable coloration. Beyond 7.5 to 10.0, diamonds acquire a fancy yellow hue, indicating lesser value.

Cut Scale: The cut scale evaluates the diamond's cut quality. A level 0 denotes a flawless cut with perfect symmetry, high brilliance, and scintillation. The diamond's polish is impeccable, free from nicks, scratches, or chips. Grades 2 and 3 signify "excellent" and "very good" cuts, respectively, with characteristics similar to an ideal cut diamond but without the same level of perfection. Levels 3 to 4 encompass "very good" diamonds, while 5, 6, and 7 represent "fair" cuts, indicating lower cut quality. Poorly cut diamonds with apparent flaws, faulty patterns and symmetry, low brilliance, and scintillation occupy the last range from 8 to 10.