GIA Alert: CVD Rough Made to Mimic Natural Diamond

 

A 6.87 ct CVD-grown synthetic diamond Photo by Danny Bowler.

The Gemological Institute of America (GIA) has issued an important warning after examining a 6.87-carat, near-colourless CVD laboratory-grown diamond that had been deliberately fashioned to resemble a natural rough diamond crystal.

The unusual stone was submitted to GIA as a rough diamond and initially displayed a shape remarkably similar to the familiar octahedral form associated with natural diamond crystals. However, advanced laboratory testing revealed that its origin was very different.

The finding is detailed in the latest issue of Gems & Gemology and highlights an emerging challenge for the diamond industry: laboratory-grown diamonds can be deliberately fashioned to imitate the appearance of natural rough diamonds before they ever reach the cutting stage.

A CVD Diamond Designed to Look Natural

CVD, or Chemical Vapour Deposition, is one of the two principal technologies used to produce laboratory-grown diamonds. Unlike natural diamonds, which form deep within the Earth’s mantle over geological timescales, CVD diamonds are grown in controlled laboratory environments from a carbon-rich gas.

The GIA researchers believe this particular stone represents the first known example, to their knowledge, of a CVD laboratory-grown diamond being deliberately shaped into the approximate form of a natural rough diamond crystal.

The significance is not simply that the material was laboratory-grown. It is the deliberate attempt to make the synthetic material visually resemble natural rough.

According to the researchers, there appears to be little practical reason to produce a CVD diamond in this form other than an attempt at deception.

Advanced Testing Revealed Its True Origin

While its external appearance suggested a natural crystal, sophisticated laboratory analysis told a different story.

GIA used Raman spectroscopy, a powerful analytical technique capable of identifying the molecular and structural characteristics of diamond material.

The testing confirmed that the stone was CVD-grown diamond, rather than a natural diamond crystal.

This demonstrates why visual examination alone cannot always establish the origin of a rough diamond.

Natural diamond crystals can exhibit characteristic crystal forms, surface features and growth patterns. However, a laboratory-grown diamond can potentially be cut, shaped or modified to imitate some of those characteristics.

It Wasn’t Actually a True Octahedron

Closer examination also revealed that the stone was not a genuine natural octahedral crystal.

Only one pair of opposite faces was parallel, while the surfaces did not correspond to the crystallographic planes normally associated with natural diamond crystals.

In other words, the stone had been fashioned to create the impression of a natural crystal rather than actually possessing the crystallographic geometry of one.

For an experienced diamond professional, such inconsistencies may provide important clues. But the case demonstrates how sophisticated the presentation of laboratory-grown material can become.

Why Producing This Stone Would Be Difficult

Interestingly, manufacturing a CVD diamond in this form is not a simple or efficient process.

CVD diamonds are generally grown as larger blocks or plates of material. Producing a rough-looking crystal from that material requires additional cutting and shaping.

The GIA researchers noted that attempting to create a finished diamond from a CVD block while maintaining the required crystal structure would be difficult and wasteful.

A significant amount of material would be lost in the process, and the eventual polished diamond would be considerably smaller than one cut directly from the original as-grown CVD block.

That makes the decision to create a crystal-shaped CVD diamond particularly significant.

From a commercial perspective, it would make little sense to sacrifice valuable CVD material simply to create a rough crystal appearance unless there were another objective.

A Warning for the Rough Diamond Trade

The discovery is particularly relevant to the rough diamond market, where the first assessment of a stone can be based heavily on its external appearance, crystal morphology and surface characteristics.

For generations, experienced diamond buyers have learned to recognise natural crystal forms and the features associated with different types of rough.

But laboratory-grown technology is evolving rapidly.

The GIA case demonstrates that the industry cannot assume that a convincing natural-looking crystal is necessarily natural.

Appearance is not proof of origin.

This is an important distinction for dealers, manufacturers, wholesalers, retailers and consumers alike.

Could This Lead to New Rough-Diamond Screening Technology?

Perhaps the most significant aspect of the GIA report is that the researchers believe the industry could respond if stones of this type become more common.

They suggest that an immediate screening solution for rough diamonds could potentially be developed by adapting existing instruments currently used to screen polished diamonds.

This could become increasingly important as laboratory-grown diamond production expands and techniques for disguising laboratory-grown material become more sophisticated.

The diamond industry already relies on a combination of spectroscopy, fluorescence, photoluminescence and other advanced analytical technologies to separate natural diamonds from laboratory-grown diamonds.

The challenge now is ensuring that these technologies remain effective before a diamond reaches the polishing stage.

What This Means for the Diamond Industry

The GIA discovery is a reminder that the distinction between natural and laboratory-grown diamonds is not simply a matter of appearance.

A laboratory-grown diamond can possess the same basic chemical composition and crystal structure as a natural diamond. The crucial difference is origin.

As laboratory-grown diamond manufacturing becomes more sophisticated, the industry must continue to develop reliable methods for establishing that origin.

For professional diamond buyers, this reinforces the importance of purchasing rough and polished diamonds through reputable channels and using appropriate laboratory testing when the provenance or origin of a stone is in question.

For consumers, it reinforces another important principle:

If the origin matters, test the stone.

A diamond may look natural.

It may have been deliberately shaped to look natural.

It may even convince an experienced eye at first examination.

But sophisticated laboratory analysis can reveal what the eye cannot.

The Bigger Picture

The GIA case should not be interpreted as evidence that every unusual rough diamond is suspicious, nor does it suggest that CVD technology itself is a problem.

Laboratory-grown diamonds are a legitimate category of diamond material and can be accurately identified when appropriate testing is undertaken.

The concern arises when laboratory-grown material is intentionally presented in a manner designed to create the impression that it is natural.

That is where the industry’s established systems of disclosure, screening, verification and independent grading become critical.

As technology advances on both sides of the industry, the race between diamond-growing technology and diamond-identification technology is likely to continue.

The 6.87-carat CVD crystal examined by GIA may be an unusual case today. But it provides a valuable warning about what could become a more significant challenge tomorrow.

For the modern diamond industry, the lesson is clear: a natural-looking rough crystal is not necessarily a natural diamond. Advanced scientific testing remains the ultimate safeguard.

The changing romance of diamonds and jewellery

 

Swarovski’s chief executive has told the Financial Times that falling prices for laboratory-grown diamonds are enabling more women to buy diamond jewellery for themselves, rather than waiting for it to be given as a romantic gift.

The comments highlight a wider shift in the way consumers relate to diamonds and fine jewellery. Traditionally associated with engagements, anniversaries and other relationship milestones, diamond jewellery is increasingly being positioned as a form of personal expression, self-reward and financial independence. The romance of the diamond is not disappearing; it is becoming more personal and less dependent on a partner or a formal occasion.

Laboratory-grown diamonds have accelerated this change. As production costs and retail prices have fallen, diamond-set jewellery has become accessible to a broader customer base. Consumers who may previously have considered diamond jewellery unattainable can now enter the category at a lower price point, while those purchasing for themselves can choose pieces based on personal style rather than the expectations attached to a traditional gift.

For Swarovski, which operates across crystal, fashion jewellery and fine jewellery, laboratory-grown diamonds provide an opportunity to move further into the premium sector without the price barriers associated with natural stones. The company can present diamonds as contemporary, wearable and attainable appealing to customers who may be buying a meaningful piece to mark a personal achievement, career milestone or simply a moment of self-indulgence.

This shift towards self-purchase is one of the most closely watched developments in jewellery and watches. Brands ranging from De Beers to newer laboratory-grown specialists are adapting their communications to focus less exclusively on romance between couples and more on individuality, empowerment and personal reward. The message is increasingly that a diamond does not need to be given by someone else to be emotionally significant.

The trend also creates challenges for the natural diamond sector. Producers are already facing pressure from weaker rough-diamond prices, changing consumer expectations and growing scrutiny around provenance and sustainability. If consumers buying for themselves increasingly choose laboratory-grown diamonds because of their affordability and compatibility with modern messaging, natural diamond companies will need to work harder to communicate the value of rarity, origin, longevity and heritage.

The key question for the industry is whether self-purchase becomes a permanent pillar of jewellery marketing rather than a temporary response to changing consumer behaviour. As the boundaries between romantic gifting and personal luxury continue to blur, the meaning of the diamond itself is evolving from a symbol primarily of commitment between two people to one that can also represent ambition, independence and self-expression.

For the DCLA, this changing relationship with diamonds underlines the importance of communicating the distinct qualities of natural diamonds while recognising the broader cultural shift taking place across the jewellery market. The future of the category may depend on its ability to preserve the emotional power of the diamond while expanding the occasions, customers and stories connected to it.

GIA Examines a Remarkable Colour-Treated Purple Diamond

 

The Gemological Institute of America (GIA) has examined a fascinating 3.93-carat Type Ib purple diamond that had undergone colour treatment involving irradiation and annealing, revealing unusual internal growth patterns and a distinctive arrow-like feature visible under deep ultraviolet light.

The rough purple diamond was submitted to the GIA laboratory in Dubai for analysis. Its unusual appearance and internal characteristics prompted further examination, with the findings published in the spring 2026 issue of Gems & Gemology.

Irradiation and Annealing Created the Purple Colour

GIA determined that the diamond had undergone a combination of irradiation followed by low-temperature annealing to produce its intense purple bodycolour.

The conclusion was based on several factors, including the diamond’s intense colour, its Type Ib classification, and the presence of nitrogen-vacancy (NV) centres. These defects within the diamond’s crystal structure play an important role in producing its unusual colour.

Purple diamonds can display colour as a result of transmission windows in the blue and red regions of the visible spectrum. In this particular stone, however, the introduction of NV centres produced an intense, relatively pure purple bodycolour without the pink component that is commonly associated with NV-related coloration.

DiamondView Reveals a Hidden Arrow

One of the most intriguing aspects of the examination was revealed through DiamondView imaging. Under deep ultraviolet (UV) illumination, the diamond displayed a dark, nonfluorescing area resembling an arrow pointing towards the profile of an elongated diamond.

The remainder of the stone displayed a bright orange fluorescence, which was likely associated with NV defects.

The contrast between the fluorescent and nonfluorescent areas provided a remarkable view of the diamond’s internal growth history. GIA concluded that the distinctive pattern reflected multiple growth sectors formed naturally as the diamond developed.

A Natural Pattern That Looks Like an Arrow

The arrow-like feature is particularly interesting from a gemological perspective. Arrow patterns produced through precise diamond polishing can be highly valued for their optical appearance, but this example is very different.

Here, the arrow appears to be a form of pareidolia a phenomenon where the human eye recognises a familiar shape within an otherwise random pattern.

The feature is not an inclusion deliberately positioned or created during polishing. Instead, it is the result of contrasting growth sectors within the diamond and becomes visible because of their different fluorescence responses under deep UV illumination.

Why Advanced Laboratory Testing Matters 

This diamond is an excellent example of why sophisticated laboratory techniques are essential when examining unusual or treated diamonds.

Its colour, diamond type, NV centres, fluorescence characteristics and growth patterns all contributed to GIA’s determination that the purple colour was artificially induced through irradiation and subsequent low-temperature annealing.

For consumers and the diamond trade, identifying whether a colour is natural or treated can have a significant impact on a diamond’s description, rarity and value. Features that may be invisible under normal lighting can become highly revealing when examined using advanced instruments such as DiamondView and other spectroscopic techniques.

This remarkable purple diamond demonstrates that every diamond has a story and sometimes, that story can literally appear as an arrow hidden inside the stone.

At DCLA, we believe every diamond deserves to be examined, documented and understood, not simply admired.

DCLA — independent gemmological expertise and diamond testing in Australia since 2001.

 Source: DCLA

Diamond Light Return: How Cut, Angles and Facets Control the Way a Diamond Performs

 

A diamond is far more than a beautiful gemstone. It is a precisely engineered optical crystal, and the way it interacts with light is governed by the same fundamental principles that apply to a prism.

When light enters a diamond through one of its facets, it does not simply travel straight through the stone. As it passes from air into diamond, the change in optical density causes the light to refract, or change direction. From there, the internal angles of the diamond determine whether that light continues through the stone, escapes, or is reflected back through the diamond.

This interaction between refraction, reflection and facet geometry is fundamental to a diamond’s brightness, fire and overall visual performance.

The Critical Role of Diamond Angles

The angles within a diamond are critical because light must follow a carefully controlled path through the stone.

When light enters through the table or upper crown facets, it is refracted as it enters the diamond. The light then travels towards the pavilion, the lower portion of the stone. If the pavilion angle is appropriate, the light strikes the pavilion facet at an angle that allows it to be reflected rather than immediately escaping through the bottom of the diamond.

The reflected light is then redirected across the stone towards another pavilion facet, where it can be reflected again. From there, it travels back towards the crown and eventually exits through the upper facets and table, returning light towards the observer.

This process is commonly referred to as light return.

In simple terms, the diamond is acting as a sophisticated optical system. The facets are the surfaces that control the direction of the light, while the angles determine whether the light is retained, reflected and ultimately returned to the viewer.

Refraction and Reflection Working Together

Two optical principles are particularly important.

Refraction occurs when light changes direction as it passes from one material into another, such as from air into diamond.

Reflection occurs when light strikes an internal surface and is redirected rather than passing through it.

The relationship between these two principles is what gives a well-cut diamond its characteristic brightness.

The pavilion is particularly important. If the pavilion is too shallow, light can escape through the bottom of the stone rather than being reflected back towards the crown. If it is too deep, light can also be directed away from the viewer.

The objective is therefore not simply to make a diamond deeper or shallower. The pavilion, crown, table and other facets must work together within appropriate proportional relationships.

Why Proportions Matter

A diamond can contain excellent material and still appear dull if it has been cut with proportions that do not manage light effectively.

A well-proportioned diamond allows a significant amount of the light entering through the crown to be redirected back towards the observer.

This is one of the reasons round brilliant diamonds have become so highly developed from an optical and scientific perspective. Their high degree of symmetry makes it possible to study and define their proportions with considerable precision.

The round brilliant is generally regarded as the most symmetrical of the major diamond shapes, allowing established proportion systems and ideal-cut concepts to be applied more consistently.

One of the historic milestones in the development of ideal-cut theory was Tolkowsky’s 1919 Ideal Cut, developed by Marcel Tolkowsky. His work examined the mathematical relationship between a diamond’s proportions and its ability to return light, helping establish the foundations for modern diamond-cut analysis.

Why Fancy-Cut Diamonds Behave Differently

Fancy shapes introduce a much more complicated optical challenge.

Unlike the round brilliant, many fancy shapes are not symmetrical in all directions. This includes elongated oval, marquise, pear and elongated cushion-cut diamonds.

The length and width of these diamonds can have significantly different proportions. Consequently, the pavilion geometry along the length of the diamond may not behave in exactly the same way as the pavilion geometry across its width.

This can produce differences in light return across different areas of the stone.

For example, an elongated oval may have one optical response along its length and another across its width. The same principle can apply to marquise and pear shapes, where the geometry changes considerably from the centre towards the points.

This is one reason why two diamonds of the same shape, carat weight and colour can look noticeably different when viewed side by side.

The Pavilion Is the Engine Room of Light Return

When examining diamond performance, the pavilion deserves particular attention.

The pavilion facets are responsible for much of the internal reflection that sends light back towards the crown. Their angles determine the path that light takes once it has entered the stone.

In an elongated diamond, achieving consistent light return across the entire stone can be particularly challenging. The cutter must balance the pavilion angles, crown facets, table and overall depth to manage light across different sections of the diamond.

A change in one area can influence another.

This is why diamond cutting is both an art and a science. The cutter is not simply removing material to create a particular outline. They are creating a three-dimensional optical structure in which thousands of possible light paths interact.

Facet Modifications Can Influence Light Return

Modern cutting techniques allow cutters to modify facet arrangements and proportions to improve the visual performance of a diamond.

Changes to facet size, placement, depth and symmetry can influence the way light travels through the stone. In some designs, modifications can help compensate for the optical challenges created by an elongated or unusual shape.

A cutter may adjust the geometry of the stone so that particular areas interact with light more effectively. However, these modifications always involve compromises. Improving light performance in one area can potentially affect another.

The goal is therefore to find the best balance between shape, proportions, symmetry, weight retention and optical performance.

Why Two Diamonds Can Look Completely Different

This explains why carat weight alone is never enough to judge a diamond.

Two diamonds can both weigh one carat, have the same colour and clarity grades, and yet appear very different when placed next to each other.

One may look bright and lively, while the other may appear darker or have areas where light escapes.

The difference can be found in the way each stone has been cut.

The combination of table size, crown angle, pavilion angle, total depth, girdle proportions, facet arrangement and symmetry determines how the diamond interacts with incoming light.

For fancy shapes, the challenge becomes even greater because the optical behaviour can vary across the stone.

Looking Beyond the Sparkle

When you look at a diamond and see flashes of white light, coloured fire and areas of brightness and contrast, you are seeing the result of physics occurring inside the crystal.

The diamond has not simply been polished to look attractive. Its facets have been arranged to control light.

Understanding this is important for both consumers and professionals. A diamond should be evaluated not only by its carat weight, colour and clarity, but also by the quality of its cut and the way its proportions and facets work together.

At the Diamond Certification Laboratory of Australia (DCLA), understanding the relationship between a diamond’s proportions, symmetry and optical behaviour is an important part of professional diamond assessment.

The next time you look into a well-cut diamond, remember what is happening beneath the surface: light enters, changes direction, travels through carefully calculated angles, reflects from pavilion facets and is redirected back towards you.

That journey of light is what creates the life and brilliance we see in a diamond.

Selling a Diamond? Here’s the Paperwork You Need to Know About

 

Selling a diamond is very different from selling an ordinary piece of jewellery. A diamond can be worth thousands, tens of thousands, or considerably more, but its value depends on characteristics that cannot simply be judged by looking at the stone.

If you are thinking about selling a diamond, one of the most important questions you should ask is:

“Do I have an independent diamond grading report for my stone?”

If the answer is no, obtaining an independent report before you sell can be one of the smartest steps you take.

What paperwork do you need to sell a diamond?

There is no single piece of paperwork that every seller must have in every situation. However, the more information you can provide about a diamond, the easier it is for a potential buyer to establish exactly what they are purchasing.

Ideally, you should have:

• An independent diamond grading report or certificate
• Your original purchase invoice, if available
• Any previous valuation or insurance documentation
• Details of the jeweller or supplier from whom the diamond was purchased
• Any previous laboratory report
• Information about whether the diamond is natural or laboratory-grown
• Any documentation relating to treatments or enhancements
• The original jewellery purchase paperwork, if the diamond is still mounted

Not having these documents does not mean you cannot sell your diamond.

However, it can make the process more difficult.

A buyer may have to conduct their own examination and testing before being prepared to make an offer. Until the diamond’s identity and quality have been independently established, there may be uncertainty surrounding its value.

What if I don’t have a diamond certificate?

This is extremely common.

Many people inherit diamonds, purchase jewellery years ago, lose the original paperwork, or simply were never given an independent grading report when they bought the diamond.

You may have a valuation from an insurance company or jeweller, but it is important to understand that a valuation and a diamond grading report are not the same thing.

A valuation generally provides an estimated monetary value for a particular purpose and point in time.

A grading report describes the diamond itself.

It can document characteristics such as carat weight, colour, clarity, measurements, cut, polish, symmetry, fluorescence and other identifying characteristics. DCLA also identifies whether a diamond is natural or laboratory-grown and records relevant treatments or enhancements.

That distinction becomes particularly important when you are trying to sell.

Why an independent diamond report matters

Imagine trying to sell a car without knowing its exact model, engine size, year or service history.

The buyer may still be interested, but they have less information and therefore more uncertainty.

Diamonds work in a similar way.

A reputable independent laboratory removes much of that uncertainty by providing an objective assessment of the stone.

Instead of telling a potential buyer:

“I was told this is a 1.50-carat G colour VS1 diamond.”

you can provide an independent laboratory report documenting the diamond’s characteristics.

That gives the buyer something they can examine, verify and compare.

DCLA reports include a unique certificate identification number, detailed diamond characteristics and are securely archived, with an online certificate verification service available.

Why certification can help you sell internationally

One of the biggest advantages of having a recognised independent laboratory report is that you are no longer relying solely on your own description of the diamond.

A properly documented diamond can be presented to jewellers, dealers, insurers and potential buyers in different markets with a much greater level of confidence.

This is particularly important if you are considering selling outside Australia.

DCLA is an internationally recognised Australian diamond grading laboratory, established in 2001 to provide certification in Australia according to International Diamond Council (IDC) standards. DCLA states that its reports are produced in accordance with IDC and CIBJO standards and that the laboratory is internationally accredited and recognised.

DCLA is also listed on RapNet and IDEX, giving its reports additional recognition within the international diamond trade.

The result is simple: a properly documented diamond is easier for a potential buyer to understand, verify and compare.

Why choose DCLA?

If you have a diamond without a report, having it independently graded by a recognised laboratory can give you a significant advantage when you eventually decide to sell.

DCLA has been operating since 2001 and was established specifically to bring internationally compliant diamond grading to the Australian market.

The laboratory grades diamonds according to International Diamond Council standards and uses advanced testing technology to identify natural and laboratory-grown diamonds, detect treatments and assess the diamond’s characteristics.

Just as importantly, DCLA operates independently.

The diamond is assigned a unique identification number when it enters the laboratory, with customer information removed from the grading process. This helps ensure that the grading assessment is independent and not influenced by the commercial interests of a buyer or seller.

Consistency is important when selling a diamond

Diamond grading is not simply about putting a number on a stone.

Small differences in colour, clarity, cut and other characteristics can have a significant effect on market value.

This is why consistency and recognised grading standards matter.

A report from an independent laboratory gives the market a common reference point.

Instead of different buyers relying on different descriptions, they can refer to the same documented characteristics.

That can be particularly valuable when a diamond is being offered to buyers outside your local market.

A certificate is not a valuation

There is one important point every diamond owner should understand.

A diamond grading report is not a valuation.

The report describes the diamond; it does not guarantee what somebody will pay for it.

The eventual selling price depends on many factors, including current market conditions, the diamond’s characteristics, demand, the buyer, and whether the stone is being sold privately, through the trade or as part of a jewellery piece.

However, knowing exactly what you have puts you in a much stronger position when discussing price.

What happens if the diamond is still in a ring?

If your diamond is mounted in a ring or other jewellery, the laboratory may need to examine the stone carefully and, depending on the setting, remove it to provide an accurate grading assessment.

DCLA notes that accurate grading of the diamond itself can require the stone to be loose. Simple claw settings may sometimes be removed in the laboratory, while more complex settings such as bezel settings may require additional consideration because removal can potentially affect the jewellery.

This is another reason to have the diamond assessed professionally before you begin the selling process.

Don’t rely on paperwork produced by the seller

An important principle when buying or selling diamonds is independence.

A document produced by a retailer, dealer or other party with a financial interest in the diamond is not the same as an independent laboratory grading report.

The purpose of an independent laboratory is to assess the diamond objectively rather than to sell it.

DCLA specifically recommends checking that a diamond report comes from an independent laboratory rather than from a merchant or retailer with a financial interest in the stone.

Your diamond may be worth more than you think — or less

One of the biggest mistakes diamond owners make is assuming that an old valuation or the price originally paid tells them what their diamond is worth today.

Neither necessarily reflects today’s market.

The diamond market changes, and the price originally paid for a piece of jewellery can include manufacturing, design, retail margins, branding, GST and other costs that may not be recoverable when the item is sold.

Before selling, it is therefore important to establish exactly what you own.

What is the diamond?

Is it natural or laboratory-grown?

What is its carat weight?

What are its colour and clarity grades?

How has it been cut?

Is it treated?

Does it have an identifiable laboratory report?

Once these questions have been answered, you can approach the selling process with considerably more information.

Have a diamond but no certificate?

Don’t assume you have a problem.

If you have inherited a diamond, lost the original paperwork, bought an older diamond without certification, or simply want to establish exactly what you own before selling, an independent DCLA grading report can provide the documentation you need.

With DCLA’s international recognition, IDC-based grading standards, secure report records and verification system, your diamond can have documentation that is meaningful beyond simply having a piece of paper in your hand.

Before you sell your diamond, know what you have.

A professional, independent diamond grading report can give you the confidence to approach the market with accurate information and can make it easier for potential buyers to assess your stone whether they are in Australia or looking at the diamond from an international market.

DCLA Independent Diamond Certification Since 2001

If your diamond does not have a current independent grading report, DCLA can assess and certify the stone, providing a detailed record of its characteristics and identity.

Don’t sell your diamond based on what you think it is worth.

Get the diamond independently assessed, documented and certified first.