How Are Lab-Grown Diamonds Graded?

The process generally begins by establishing what the submitted stone actually is. A laboratory may first determine whether the material is diamond and whether its origin is natural or laboratory-grown. It can then measure and weigh the diamond and evaluate relevant characteristics such as colour, clarity, cut, polish, symmetry and fluorescence according to its own laboratory methodology.

IGI describes a structured process involving anonymous intake, carat-weight measurement, optical measurements, colour and fluorescence assessment, clarity and finish grading, cut assessment, independent verification by multiple gemmologists, grading controls, inscription and final report preparation.

The final document should therefore be understood as the result of a laboratory process, not simply one person looking through a loupe and choosing a grade.

Before quality can be meaningfully assessed, the laboratory needs to understand what material it is examining. This is especially important because a colourless stone presented as "diamond" could potentially be a natural diamond, laboratory-grown diamond or a simulant such as moissanite or cubic zirconia.

IGI states that it screens submitted gemstones using specialised technologies to determine whether they are naturally mined, laboratory-grown or simulant material before further gemmological assessment.

This means origin identification and quality grading are connected but separate questions. First: What is this stone? Then: What are its measurable quality characteristics?

A lab-grown diamond cannot always be separated from a natural diamond simply by looking at it. Both are diamond material and can share essentially the same fundamental physical and optical properties.

Specialist laboratories therefore examine characteristics associated with how the diamond grew. These can include growth patterns, fluorescence behaviour, trace elements, inclusions and spectroscopic features associated with atomic-level defects. The laboratory can then determine whether the diamond's growth history is consistent with natural formation, HPHT growth or CVD growth.

That origin determination is fundamental because a laboratory-grown diamond should be reported as laboratory-grown rather than represented as natural.

For the deeper identification question, read Can You Tell a Lab-Grown Diamond from a Natural Diamond?

Professional grading involves more than examining the stone. The diamond also needs to be securely tracked throughout the process. IGI states that diamonds entering its grading process receive a unique automatically generated identification number and are graded anonymously. The stone moves through controlled stages while being electronically tracked through the laboratory.

Anonymity helps separate the grading decision from the commercial identity of the submitter. The grader is evaluating the diamond rather than the retailer or brand selling it.

Carat is the standard unit used to express diamond weight. One metric carat equals 0.20 grams, or 200 milligrams. In laboratory grading, a loose diamond can be weighed directly on a highly sensitive balance.

IGI states that its grading balances are calibrated to four decimal places and that carat weight is reported to two decimal places on the grading report. GIA likewise describes using electronic micro-balances capable of recording diamond weight with extremely high precision before the final reported value is prepared.

Carat is therefore a measured physical property. It is not determined by how large the diamond looks.

For the full distinction, read Lab-Grown Diamond Carat Weight Explained and Diamond Carat Weight vs Size.

Laboratories also measure the physical geometry of the stone. IGI describes using gemstone-specific optical measuring equipment to build a three-dimensional representation of the diamond and record proportions, facet angles and key measurements. These measurements may include length, width, depth, diameter and other proportion data depending on the shape.

This information matters because two diamonds can have the same carat weight yet different physical dimensions. Measurements can also contribute to cut assessment. For a round brilliant, proportions such as table size, total depth, crown angle and pavilion angle can influence light performance and therefore become relevant to the overall cut result.

Colour grading is performed under controlled viewing conditions rather than ordinary shop lighting. Lighting and surroundings can alter how colour appears to the human eye, so laboratories use standardised environments to reduce those variables.

IGI states that D-to-Z colour grading is performed with the diamond viewed through the side while placed face-down and compared in a controlled environment. Multiple graders submit colour opinions independently, and the result is finalised when sufficient agreement is reached.

This is important because colour grading is not simply: "This looks white to me." It is a comparative laboratory assessment.

For detailed interpretation of D, E, F, G, H and the wider colour scale, read Lab-Grown Diamond Colour Grades Explained.

Fluorescence is separate from diamond colour. A laboratory can expose the diamond to ultraviolet radiation and observe whether the stone emits visible light. Where applicable, the report may describe the fluorescence strength and colour.

IGI incorporates fluorescence assessment into its grading workflow and records it separately from ordinary colour grading. A diamond's fluorescence result therefore should not be confused with its colour grade. They describe different observations.

Clarity concerns internal and surface characteristics visible under standardised examination. IGI states that clarity grading is performed at 10× magnification and considers the visibility, size, number, location and nature of internal and surface characteristics.

Those details matter. Two diamonds can contain the same general type of inclusion and still receive different clarity grades because the characteristics differ in position, size, relief or visibility. The laboratory may also record significant clarity features on a plotted diagram where the report service includes one.

For the full grading scale and inclusion terminology, use Lab-Grown Diamond Clarity Grades Explained

Yes. The fact that a diamond grew in controlled conditions does not mean the resulting crystal is automatically flawless. HPHT and CVD growth can produce their own internal characteristics. A laboratory-grown diamond can therefore receive different clarity results just as individual natural diamonds vary in clarity.

"Lab-grown" is an origin description. It is not shorthand for: Flawless or: VVS.

Polish refers to the quality and condition of the diamond's polished facet surfaces. It is one of the craftsmanship characteristics created during cutting and finishing rather than during crystal growth itself. A diamond can have a desirable colour and clarity while still receiving a weaker polish result.

This is why polish should remain a separate field rather than being merged into a generic claim that the diamond is simply "well cut". IGI states that all diamond shapes and colours receive craftsmanship grades for polish and symmetry within its relevant grading reports.

Symmetry evaluates the precision of the diamond's shape and facet arrangement. The grader considers whether corresponding facets are properly aligned, whether the outline is balanced and whether other symmetry-related features meet the applicable standards.

Again, symmetry is not identical to overall cut. A report might show one result for cut, another for polish and another for symmetry. Those should be read independently.

Cut grading is more complicated than colour or carat because diamond shape and laboratory methodology matter. For round brilliant diamonds, IGI assesses proportions, polish, symmetry and visual-performance-related factors. Its current round brilliant system has Excellent-Ideal as its highest overall cut grade.

IGI also offers cut grading for fancy-shaped diamonds. Its current system combines finish, proportions, shape-specific requirements and light-return considerations, with fancy-shape cut results ranging from Excellent to Poor when that service is used.

This is important because older generic advice often states that fancy shapes can never receive an overall cut grade. That is not universally true across current laboratories.

No laboratory's terminology should automatically be transferred to another. GIA's traditional overall cut-grading system for natural diamonds applies to standard round brilliant diamonds within the applicable D-to-Z range. GIA evaluates brightness, fire, scintillation, weight ratio, durability, polish and symmetry within that system.

For current D-to-Z laboratory-grown diamonds, GIA's Premium/Standard Quality Assessment incorporates a cut criterion for round brilliants rather than providing the same lab-grown reporting format it used before October 2025. Under the current system, a qualifying round brilliant must meet Excellent cut for Premium, while Very Good is the minimum round-brilliant cut criterion for Standard. Fancy shapes do not use that round-brilliant cut criterion within the current GIA Quality Assessment.

For the detailed cut systems, read Lab-Grown Diamond Cut Explained.

Diamond grading is not intended to rest on one uncontrolled opinion. IGI states that colour and clarity analyses involve multiple gemmologists who submit their assessments independently. The results are finalised once sufficient agreement or consensus has been reached. This helps improve consistency.

GIA likewise describes using independent grader opinions and quality-control procedures within its diamond-grading processes. This does not mean gemmological grading is mathematically identical to measuring mass. Some characteristics require trained visual judgement within standardised conditions. That is precisely why laboratories use controlled methodology and multiple graders.

Some parts are direct physical measurements. Carat weight and dimensions are measured. Other characteristics, particularly colour and clarity, involve trained human assessment within defined laboratory standards. Cut grading can combine physical measurements with models, workmanship assessment and optical-performance criteria depending on the laboratory.

Professional grading therefore seeks repeatable, standardised assessment, rather than pretending every characteristic is generated by a single machine without expert judgement.

Lab-grown diamond reporting can contain information that does not usually arise in the same way for natural-diamond consumer descriptions. For example, the laboratory may identify whether the stone was created by CVD or HPHT. A report may also state whether evidence of post-growth treatment is present.

IGI says the growth process and presence of treatments can be recorded in the comments section upon request. Growth method and treatment should not be confused. A diamond can be CVD-grown and later HPHT-treated.

For the full distinction, use CVD vs HPHT Lab-Grown Diamonds.

Do not use that blanket rule. A treatment disclosure tells you something about the diamond's manufacturing history. The colour, clarity, cut, carat and finish characteristics are still evaluated according to the laboratory's relevant methodology. A post-growth treatment does not automatically tell you the final quality of the stone. The important point is accurate disclosure.

Some laboratory reporting systems connect the physical diamond with its documentation through microscopic girdle inscriptions. IGI states that every laboratory-grown diamond it grades receives an inscription identifying its laboratory-grown origin, while its report-number LaserScribe system provides an additional means of linking the stone to its report.

GIA's current D-to-Z lab-grown Quality Assessment also requires the submitted stone's girdle to be inscribed with "Laboratory-Grown" and the relevant GIA quality-assessment number. The inscription helps with identification. It is not itself the grading result.

For that subject, read What Is a Diamond Laser Inscription?

Once grading or assessment has been completed, the results are assembled into the relevant report or assessment document. IGI says its process includes final verification, report preparation and subsequent online availability of the digital report through its verification system.

The document can then be used to understand the diamond's laboratory findings and compare it with other stones. But a report should not be interpreted as a promise about every aspect of the jewellery purchase. Grading and valuation are different.

No. A grading report documents gemmological characteristics under the issuing laboratory's service. An appraisal estimates financial value for a particular purpose. Those are different services. A 1.50 ct F VS1 laboratory-grown diamond can have those same gemmological characteristics regardless of what one particular retailer charges for it. A grading laboratory does not automatically determine the correct retail or future resale price.

IGI continues to use a detailed grading-report format for laboratory-grown diamonds. Its current Laboratory Grown Diamond Report can include the stone's description and laboratory-grown origin, shape and cutting style, measurements, carat weight, colour, clarity and cut information, along with proportions and other relevant observations depending on the report.

For colour, IGI uses its D-to-Z framework for colourless-to-light-colour diamonds. For clarity, its lab-grown report uses categories including IF, VVS, VS, SI and I. For round brilliants, IGI provides overall cut assessment; its current methodology also provides an optional fancy-shape cut-grading system. Polish and symmetry are recorded independently.

This means an IGI lab-grown diamond can still be described using detailed individual quality results.

GIA's current approach is materially different. On 1 October 2025, GIA replaced its previous D-to-Z laboratory-grown diamond reporting service with its Laboratory-Grown Diamond Quality Assessment for qualifying stones. Under this current system, qualifying diamonds are assigned one of two overall classifications: Premium or: Standard.

A diamond that does not meet the minimum criteria for Standard does not receive the Quality Assessment. This means GIA's current lab-grown document should not be described as though it simply provides the same detailed nomenclature used on its natural-diamond grading reports.

Premium is an overall assessment, not a new individual colour grade or clarity grade. To qualify as Premium under GIA's current criteria, the laboratory-grown diamond must meet all applicable Premium thresholds. Those include VVS clarity or higher, D colour, Excellent polish and symmetry and, for round brilliant diamonds, Excellent cut.

Because the requirements are combined, you should not treat "Premium" as meaning only: D colour or only: VVS clarity. It means the stone met the complete applicable Premium criteria.

Standard is also an overall classification. GIA's current minimum Standard thresholds include VS clarity, E-to-J colour, Very Good polish, Very Good symmetry—with Good symmetry permitted for fancy shapes—and Very Good cut for applicable round brilliant diamonds.

A qualifying stone can contain a combination of Premium-level and Standard-level characteristics and still receive the overall Standard result. Again, Standard is not an individual colour or clarity grade.

Not reliably as a one-to-one conversion. The two laboratories currently report lab-grown diamonds differently. For example, an IGI report might directly state a colour and clarity grade. GIA Premium tells you the diamond met its overall Premium thresholds.

Do not rewrite: GIA Premium as: IGI D/VVS1 unless an actual IGI report independently says that. Likewise, do not convert an IGI F/VS1 diamond into "GIA Standard" as though the laboratories had issued equivalent documents. Each laboratory's result should remain attached to the system that produced it.

The answer is: the same broad quality concepts can apply, but current reporting is not universally identical. Carat still measures weight. Colour and clarity remain meaningful characteristics. Cut, polish and symmetry remain important to polished-diamond quality.

But laboratories can use different report structures and different terminology. IGI continues detailed 4Cs-style reporting for lab-grown diamonds. GIA now deliberately separates its D-to-Z laboratory-grown assessment terminology from its natural-diamond nomenclature. Therefore, any article claiming all lab-grown diamonds are "graded exactly the same way as mined diamonds" needs qualification.

When announcing the 2025 change, GIA said most laboratory-grown diamonds submitted to it fall within a relatively narrow range of colour and clarity and that descriptive quality terminology was therefore more appropriate for manufactured diamonds. GIA consequently moved from its previous natural-diamond-style lab-grown nomenclature to Premium and Standard classifications.

Whether a buyer prefers that system or IGI's more granular reporting format is a separate question. The key point for Aurelia is simply to describe each laboratory accurately.

There is no need for this article to declare one laboratory universally better. They currently communicate results differently. A detailed IGI report may appeal to a buyer who wants individual colour, clarity, carat and cut information. GIA's current assessment deliberately groups qualifying lab-grown diamonds into broader Premium and Standard quality classifications.

The useful buyer question is: What information does this particular report provide, and does that information help me compare the diamond accurately?

Identification asks what the stone is. Grading or quality assessment asks what characteristics the identified diamond possesses. For a lab-grown diamond, identification may establish: this is laboratory-grown diamond. The subsequent grading process may then assess its carat weight, dimensions, colour, clarity, cut and finish according to the laboratory's system.

Those functions should not be confused. A diamond tester indicating "diamond" does not automatically provide colour, clarity or cut grades. Likewise, a grading result should be connected to the correctly identified physical stone.

Grading happens in the laboratory. Verification happens when a buyer or seller checks that the report is genuine and corresponds with the diamond being offered.

For example, an IGI report may have been correctly issued after a full grading process. A later buyer can then retrieve that report from IGI using the report number. But: report found does not automatically mean: physical diamond matched. The stone's inscription, measurements, carat, shape and other details can be compared with the report.

For that process, read How to Verify an IGI Certificate Number.

No. A laboratory report records the findings from a specific examination. A diamond can later be resold with the same report if it remains the same stone and the report continues to describe it appropriately.

However, significant repolishing, recutting, damage or other changes can potentially alter characteristics enough that a new assessment becomes useful or necessary. The report should therefore be treated as documentation of a specific examined state, not a magical label independent of the physical diamond forever.

Minor differences between reputable grading outcomes are possible because some elements of diamond grading involve expert judgement within each laboratory's methodology. More importantly, the laboratories may now use fundamentally different reporting frameworks for lab-grown diamonds.

For example, current IGI and GIA lab-grown documents may not even express quality using the same type of final terminology. So buyers should not expect every document to line up field for field.

Yes. Carat is only one quality characteristic. Two 1.00 ct lab-grown diamonds can differ substantially in colour, clarity, cut, polish, symmetry, dimensions and visual appearance. IGI explicitly notes that diamonds of identical carat weight can receive different colour, clarity and cut results.

This is why carat should never be used as a shorthand for overall quality.

Not necessarily in every practical comparison. A higher clarity result may represent microscopic differences you cannot see without magnification. A higher colour grade may be visually subtle once the diamond is mounted. Meanwhile, cut can have a substantial influence on visible light performance.

Laboratory grading provides structured information. The buyer still needs to decide which characteristics matter most to them.

No formal grading result universally guarantees what every person will perceive as eye-clean. "Eye-clean" is a retail and consumer description rather than an official clarity grade. Visibility depends on the inclusion, diamond size, shape, viewing distance, lighting and eyesight.

Use the clarity result as technical information and inspect the individual stone where practical.

Not as a single universal "sparkle grade". Cut assessment can incorporate aspects of light performance. For example, IGI's round brilliant methodology considers brightness, fire, scintillation and pattern as part of its cut work, and it also offers separate Light Performance reporting. GIA's round brilliant cut methodology similarly considers brightness, fire and scintillation alongside design and craftsmanship factors.

But a colour or clarity grade by itself does not tell you how sparkly the diamond will appear.

The answer depends on the laboratory. IGI currently provides an optional fancy-shape cut grading system using finish assessment, proportions, shape-specific requirements and light-return evaluation. GIA's familiar overall cut grade has traditionally been limited to standard round brilliants, and its current lab-grown Premium/Standard assessment uses an overall cut criterion only for round brilliant stones.

So a blanket statement that: "Fancy diamonds never have cut grades" is no longer correct across the industry.

Mounted-jewellery grading is more limited because the setting can obstruct access to the diamond. IGI provides specific finished-jewellery reports and states that centre-stone characteristics are assessed as the mounting permits. Where a stone was graded before mounting, standard reporting can be referenced. When it is graded while mounted, IGI may report colour and clarity as ranges and provide an estimated cut result.

This is an important reason not to expect a finished-jewellery report to contain the same level of unrestricted measurement as a loose-diamond report.

A loose stone gives the laboratory access to the entire diamond. It can be directly weighed. The girdle can be inspected. All facets can be observed. The stone can be positioned freely during colour, clarity and measurement procedures.

Once mounted, some of that access can be restricted. The report type should therefore tell you whether you are looking at a loose-diamond assessment or finished-jewellery assessment.

For the dedicated distinction, read Diamond Certification vs Jewellery Certification.

No. Issuing a complete individual laboratory report for every tiny pavé or melee diamond in a bracelet, halo or eternity ring can be impractical. Different reporting and quality-control approaches can be used for parcels and finished jewellery. A significant centre diamond creates a different documentation need from dozens of tiny accent stones.

For that purchasing decision, read Do Lab-Grown Diamonds Need Certification?

A grading report is extremely useful, but it does not answer every purchasing question. It does not automatically tell you whether the jewellery setting is well made. It does not guarantee that a retailer's price is competitive. It does not guarantee future resale value. It does not prove environmental claims. And a loose-diamond report does not automatically assess the complete ring, necklace, earring or bracelet in which the diamond is eventually mounted.

Keep the scope of the document clear.

No. A gemmological report can establish laboratory-grown origin and diamond characteristics. That does not automatically establish the energy source used by the growth facility, working conditions, carbon footprint, cutting-facility practices or complete supply-chain history. Environmental and ethical claims require their own evidence. Do not turn a grading report into a sustainability certificate.

Begin with the laboratory and report type. Then establish whether you are looking at detailed individual grades or an overall assessment framework. For an IGI report, you may see specific colour, clarity and cut information. For a current qualifying GIA lab-grown assessment, you may instead see Premium or Standard.

Then look at carat and measurements, relevant cut information, polish, symmetry and comments. Do not compare two stones using one headline grade without understanding the systems behind those results.

For the full report-reading process, continue with How to Read a Lab-Grown Diamond Certificate.

If a diamond is accompanied by an IGI report, verify the report number using IGI's official verification service. Then establish that the physical stone corresponds with the report. That second part matters. A genuine report can exist while the wrong physical stone is presented beside it. Shape, measurements, carat weight and a matching girdle inscription can help connect the report to the diamond.

For the dedicated process, use How to Verify an IGI Certificate Number.

Usually, the inscription primarily provides identifying information rather than reproducing every quality grade. The corresponding laboratory report contains the actual grading results. A report-number girdle inscription can therefore function as a bridge between the physical stone and its laboratory documentation.

For the full subject, read What Is a Diamond Laser Inscription?

Lab-grown diamond grading is a controlled gemmological process. The stone is first identified and its laboratory-grown origin established. It is then weighed and measured. Relevant colour, fluorescence, clarity, cut, polish and symmetry characteristics are assessed using standardised laboratory procedures. Multiple gemmologists and quality-control procedures may contribute to the final result. Growth and treatment information may also be recorded where applicable.

But the most important modern point is that "lab-grown diamond grading" is no longer one universal report format. IGI continues to provide detailed lab-grown reports with individual 4Cs-style information. GIA changed its applicable D-to-Z laboratory-grown service on 1 October 2025 and now uses the broader Premium / Standard Laboratory-Grown Diamond Quality Assessment.

Therefore, always read a lab-grown diamond result in the context of: which laboratory issued it, which service was used, what the reported terminology means and whether the physical diamond actually corresponds with the report.

For the 4Cs themselves, continue with What Are the 4Cs of Lab-Grown Diamonds?

For colour, use Lab-Grown Diamond Colour Grades Explained.

For clarity, read Lab-Grown Diamond Clarity Grades Explained.

For cut methodology, continue with Lab-Grown Diamond Cut Explained.

For report fields, use How to Read a Lab-Grown Diamond Certificate.

For IGI report meaning, read What Is an IGI Lab-Grown Diamond Certificate?

For verification, continue with How to Verify an IGI Certificate Number.

And for laser inscriptions connecting a physical diamond with documentation, read What Is a Diamond Laser Inscription?

When reviewing an Aurelia Royale diamond, any laboratory, report, grade, growth-method or treatment claim should be based on the documentation for that specific diamond or product, rather than a generic catalogue-wide assumption.

Where a design is not currently available for direct purchase, Join the Waitlist or submit an enquiry to register your interest.