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.

From rare treasure to 'never-ending supply': What happened to diamonds?

 

The price of diamonds has plunged and supply has surged, disrupting one of the world’s most enduring marketing stories.

Once upon a time, a diamond engagement ring was a powerful symbol of social status: the bigger the rock, the greater its cachet.

Today, ring owners posting in social media forums will often voice a different sentiment: “Does this look too big?”

The diamond industry has undergone an unprecedented shake-up in recent years due to the exploding popularity of lab-grown gems.

The price of a one-carat natural diamond has more than halved since the start of 2022, according to US industry data.

Last month, De Beers — the company that helped define the diamond industry and monopolised it for decades — suspended production at South Africa’s biggest diamond mine, citing a need to cut costs amid challenging market conditions.

It’s the latest sign that the once-booming industry is at a crossroads as collapsing diamond prices force mining behemoths to close mines, delay new projects and suspend production.

At the heart of the upheaval is a physically identical product that has upended one of the most successful luxury marketing stories ever told.

Lab-grown diamonds are real diamonds — chemically and visually identical to those found deep underground.

But rather than forming inside the Earth over a billion years or more, lab gems are created by scientists using one of two primary methods — High Pressure High Temperature (HPHT) or Chemical Vapour Deposition (CVD) — to recreate the conditions under which carbon crystallises into diamond.

It takes a matter of weeks.

How did the story of a gem forged over billions of years, and sold for generations as a symbol of rarity and exclusivity, change so dramatically in just a decade?

A history of diamond-making

After years of experimentation, the first proven human-made diamonds were created in the 1950s.

At the time, there was little concern that they could become serious competition for natural diamonds.

The early synthetic stones were small, brown and of poor quality for use in jewellery, instead used for industrial purposes such as manufacturing.

It wasn’t until the 1970s that General Electric, the American company that pioneered synthetic diamond technology, produced the first gem-quality lab diamonds.

But the technology was still too expensive to make lab diamonds commercially viable for jewellery, and the stones weren’t graded highly under gem colour and clarity standards.

A ‘diamond seed’ is a tiny, microscopic slice of diamond.

As the technology continued to improve, a turning point arrived in 2007: the Gemological Institute of America (GIA), the world’s leading independent authority on gem-grade diamonds, officially recognised lab diamonds.

The GIA began issuing reports for lab gems that year, but they represented only a tiny fraction of diamonds submitted for grading — around 0.05 per cent.

A decade later, lab-grown diamonds still only accounted for a small share of the global market.

But in the last few years, they’ve erupted into the mainstream.

Paul Zimnisky, a leading independent diamond industry analyst based in New York City, says the influx of lab gems has dramatically altered the global market.

“The technology to make those diamonds has rapidly improved, and the price to make them has come down substantially,” Zimnisky tells SBS News.

As the price has come down, that’s when I’ve really seen consumer demand pick up for the man-made diamonds, and that I would say happened within the last five years in a big way.

In 2016, a one-carat natural diamond would retail in the US for around $9,380, while a lab-grown stone of the same cut and clarity would cost $7,820, according to Zimnisky’s data.

Today, the natural diamond retails for $4,900 while the equivalent lab stone can be bought for around $850 or less.

Zimnisky estimates lab-grown stones now account for around a third of the global diamond jewellery market.

Credit: Paul Zimnisky data and analysis

In the US, the world’s largest consumer market for diamonds, six in 10 engaged couples opted for a lab diamond last year, according to annual survey data from wedding planning website The Knot.

That was a 239 per cent increase from the site’s 2020 survey.

At the same time, as lab diamonds are shifting consumer trends, they are also changing global manufacturing and production flows.

With production costs declining, manufacturers in China and India have expanded at an unprecedented scale.

In China, which dominates the global production market, the central province of Henan has become known as the nation’s “diamond capital”. In the city of Zhecheng’s many factories, hundreds of machines work around the clock to produce millions of carats each year.

Today, even experts say they can’t distinguish between a natural or lab-grown diamond without specialised equipment.

“The only way to tell the difference is either through the laser inscription, which is usually engraved on the girdle of the diamond, or through a certificate which is associated with the diamond,” Michael Cohen, managing director of the Diamond Certification Laboratory of Australia, tells SBS News.

“Other than that, you need to put it to a laboratory to actually know the difference. It’s not possible to actually see it visually through a microscope, through basic testing, even your countertop retail test.”

But De Beers has been working to change that.

The London-headquartered multinational has developed a suite of advanced screening machines, costing from around $7,900 to more than $35,000, which allow diamond sellers to distinguish between natural and lab-grown diamonds by analysing microscopic signatures left behind by their different growth processes.

The technology forms part of the company’s broader effort to persuade consumers that a diamond’s origin, rather than its composition, is an important part of its story.

The rise of the big diamond

As larger diamonds have become more affordable and visible on social media, demand for smaller stones of one carat or less has slowed.

Designs that were once reserved for celebrities and the ultra-wealthy are now well within reach for many middle-income earners.

And it’s not just the price that’s more attractive: ethical concerns over the origin of gems have been offset by the lab-grown model, which does not rely on mining or supply chains that pass through conflict zones.

On Reddit forums, it’s now common to see everyday people asking whether a diamond looks “too big” or ostentatious on their finger.

At the same time, some owners of natural diamonds have posted on social media worried that people will assume their ring is lab-grown as large diamonds become increasingly prevalent.

It reflects a generational change in consumer sentiment — one that is fast becoming an identity crisis for the natural diamond industry.

De Beers launched its own lab-grown jewellery brand in 2018 but shuttered it last year to focus on its original product.

It has outlined a plan to invest in emotionally driven campaigns that emphasise the rarity and origin of natural diamonds.

Cohen says the company realised it was giving lab-grown diamonds credibility by selling them under the De Beers banner, but its exit did little to slow demand.

Jana Bowden is a professor of marketing and consumer behaviour at Macquarie University, and says much of the identity crisis faced by major brands stems from the historical emphasis on a diamond’s exclusivity.

“Diamonds have always been seen as an absolute status symbol,” she says.

“So much of this has been driven by the perceived rarity and exclusivity of the diamonds, and of course the controlled supply of diamonds through the market, and particularly De Beers as being the pinnacle brand with the most control of the market and supply.”

From rare to abundant: The ‘forever’ diamond

At its peak in the 1980s, De Beers controlled nearly 90 per cent of the global diamond market.

Its tight control of the world’s diamond supply allowed it to stockpile excess diamonds and manage how many entered the market at any time, helping to keep prices elevated.

Through its marketing, the company famously built the idea that a diamond is rare, “forever”, and the ultimate expression of love, turning diamond engagement rings into a social norm.

It also molded societal expectations around how much an engagement ring should cost.

“Isn’t two months’ salary a small price to pay for something that lasts forever?” a 1980s De Beers ad asked.

Bowden says historic luxury brands like De Beers built lasting perceptions in consumers’ minds.

Really, we’ve been taught and we have learnt how to incorporate diamonds into our lives. This is not something that existed prior to the clever marketing campaigns.

Although diamonds are now far from rare, Bowden says many of those perceptions persist — but the market is splitting in two.

“Interestingly, the legacy branding that’s come from the original, traditional mining of diamonds is also now naturally transferred to lab diamonds as well. So consumers still have that association with exclusivity or a milestone.”

Bowden says the lab-grown diamond market is increasingly appealing to younger consumers, who are often more financially constrained and ethically motivated than older generations.

A three-carat natural diamond (left) and a three-carat lab-grown diamond (right) side by side. Source: Getty / Picture alliance

Ms Elangovan, 33, who asked to omit her first name to protect her privacy, tells SBS News she has accumulated more than 10 lab-grown and natural diamonds in her jewellery collection over the past decade or so.

While she’s fascinated by the history and rarity of a natural diamond, she can no longer justify the price when she can buy a “virtually flawless” lab equivalent at a fraction of the price.

“When I look at it, I’m like, ‘Oh, this existed millions of years before me, and it probably would [for] millions of years after me,” she says of natural diamonds.

“So on that point, labs can’t compete.”

But ultimately, she says she’s thrilled to be living in an age where beautiful jewels are accessible to more people.

“I’m intrigued [that] someone can just recreate millions of years of process in a lab,” she says.

“It’s a fascinating industry. I’m just happy I’m alive now, so I can have really pretty jewellery at a very affordable price and ethically sourced.”

Can the mined diamond industry recover?

The natural diamond industry is now facing headwinds from multiple directions.

Changing consumer spending priorities, skyrocketing operational costs, geopolitical uncertainty, and declining diamond yields have all contributed to mines closing or suspending production in recent years.

Some mines were approaching the end of their lifespan regardless, but plummeting diamond prices and the enormous cost to open new mines have made it harder to justify investment in new projects.

“I think the natural diamond industry has to collect itself and come up with a strategy to further differentiate its product from lab-grown diamonds,” Zimnisky says, adding that the industry must give consumers a compelling reason to pay 10 times as much for a natural stone.

He notes that De Beers is currently up for sale by its parent company, Anglo American, with a potential deal expected this year.

The new owner’s arrival will be “an interesting catalyst” for the industry, he says.

I think they’re probably going to pretty aggressively try to kind of reignite interest and demand and emotional appeal for natural diamonds.

For now, unless prices double or triple over the next decade, Zimnisky doesn’t expect to see significant investment in new mines or the reopening of suspended operations.

Cohen, who has worked in the industry for more than 40 years, says there’ll now be a “never-ending supply” of lab diamonds. But he expects prices may eventually increase as the significant energy required to produce them becomes more expensive — which could potentially create new ethical concerns for consumers.

He believes diamond mining will eventually come to an end, but the market for natural diamonds will endure.

“The biggest supply of diamonds will no longer come from the mine, but it’ll come from the second-hand markets,” he says.

“The diamonds don’t get destroyed. As they say, a diamond is forever.”

Credit sbs.com.au