Diamonds have a unique 'fingerprint' that can reveal their origins and tell you if you've bought the real deal

A man walks into a pawnshop and buys a diamond. 

Years later he gets it tested to see if it's the real deal and finds he has hit the jackpot.

Bingo! His diamond is an unmarked pink from Australia's famous Argyle mine and worth upwards of $50,000.

Scientist John Chapman tested the diamond in question in his laboratory in Perth last year.

The former Argyle physicist recently set up a small lab that tests diamonds and traces them back to their original source.

"[We are] looking for particular emissions from the stones that uniquely identify them as being Argyle," Mr Chapman says.

"We have techniques using, for example, two different lasers.

"My bread and butter is people bringing stones, which they've either bought before or [are] like that man who bought one from a Cash Converters, or some such place, a couple of years ago and suspected it was [an Argyle].

"And indeed it was."

Smaller, stray diamonds uncertified

In the jewellery business, spotting a real diamond from a fake is crucial and customers are keen to know the provenance of what they are buying.

When Argyle first began mining diamonds in Western Australia's east Kimberley in 1985, it certified and inscribed only the bigger stones that were over half a carat.

That was the case for more than three decades until 2016 when the value of pink diamonds soared.

The mine then began certifying pink stones as small as 0.08 carats or about 2.75 millimetres round.

Mr Chapman suspects there are more stray, unauthenticated Argyle diamonds in the market.

"There are a lot of diamonds out there that hadn't received an Argyle certificate when they were sold by virtue of the fact that the size wasn't big enough or that it went through a different channel," he says.

"Or the person just lost it, mislaid it, didn't see any value in it.

"An Argyle certificate coming from the actual company itself is considered very valuable.

"But a lot of them don't have that."

Over almost four decades of production, Rio Tinto's Argyle mine was the source of about 90 per cent of the world's pink diamonds.

Now that it has closed, the diamonds — particularly the pinks — are getting so valuable that more people are wanting to collect them.

And they are wanting to know that the diamond they are buying is a genuine article.

This is where science is stepping in.

A diamond's unique 'fingerprint'

Natural diamonds were created more than a billion years ago deep in the Earth's crust.

The diamonds were brought to the surface of the Earth by deep-seated volcanic eruptions that eventually cooled.

The precious stones were contained within what is known as kimberlite pipes, the source of many of the world's mined diamonds.

Forensic and analytical chemist John Watling says, through laser technology, scientists can "fingerprint" exactly where a diamond originates from, right down to which kimberlite pipe it was created in.

Professor Watling says the process of creation leaves a unique fingerprint on each diamond, not unlike a human fingerprint, which enables the precious stone to be traced back to its source.

"Think of it as inorganic DNA, if you like," he says.

"Because there is no such thing as, obviously, DNA in non-life form. This is the equivalent of that."

Professor Watling was at the vanguard of this science. He has been working on the fingerprint technology since the 1970s.

"The original start of this was a technique called gold fingerprinting," he says.

"In 1974, I got involved with some police work when a 747 — that was transporting boxes of lead to America from South Africa to make lead toys — had an engine problem and landed in Heathrow Airport, and they unloaded it.

"They cut one of these lead ingots in half and the core was gold.

Eventually, his team traced the plane-load of gold back to its mine of origin in South Africa.

The science pioneered by Professor Watling at Curtin University and the University of Western Australia is now being used to verify not only the provenance of gold and diamonds but artwork, coffee beans, porcelain, seafood and eggs.

'Ghost currency' in drugs, arms trade

In the 1980s and 90s, Professor Watling worked with WA police to crack the spate of gold and diamond thefts happening at the time.

In the early 90s, Argyle discovered diamonds were being stolen from the mine when pink diamonds — that were unaccounted-for — popped up in Europe.

"It fortuitously happened that the case of theft from Argyle came about and we were involved in that case, quite obviously from the start," Professor Watling says.

He says once police asked him to "fingerprint" stolen goods, the thieves often gave themselves up.

"People hear that you are going to do gold fingerprinting on them and trace them back and they know that they're not going to be able to lie," Professor Watling says.

"It says to people, 'You thought you could get away with it, but you actually can't', so they fess up in a lot of cases and we don't go to court."

Professor Watling says no matter how sophisticated the technology gets, diamonds will always be a ghost currency used by the drug and arms trade because they are so small and valuable.

"Where there's anything that's worth a lot of money, and that's easily transportable, it becomes a ghost currency," he says.

"But all of these sorts of things will still continue to be traded. It is just man's nature to be greedy, and to try to get away with it."

The rise of lab-grown diamonds

It's not just provenance technology that has become more sophisticated.

So have the means to create artificial or synthetic diamonds in a laboratory environment, that can pass as natural diamonds.

"I looked at artificial diamonds some years ago, but they were a lot less sophisticated in their production processes," Professor Watling says.

"And the contamination was high, so you can easily tell individual factories apart.

"It's more difficult these days, but we're working it out.

"So hopefully, yes, in the next very short period of time we'll have it sorted."

Even the company most synonymous with diamonds, De Beers, has dipped its toes into producing synthetic versions in a laboratory in the US.

Mr Chapman believes lab-grown diamonds will start to cut into the natural diamond market. 

"I think we can't deny that, although a lot of commentators will say otherwise," he says.

"But the reality is, they're producing something that's more consistent, which can look very much like the natural product, and be vastly cheaper."

Rio Tinto's minerals chief executive Sinéad Kaufman, who heads up the miner's diamond projects, including Argyle and the Diavik mine in Canada, believes there is a place for both synthetic and natural diamonds in the market.

"But [we] certainly recognise that the technological changes on the synthetic diamonds are probably meaning it's going to be an evolving market," she says.

And the miner is taking the influx of synthetics seriously. In June this year, it launched a trading platform designed to protect the provenance of its rare Argyle pinks.

So, would Rio Tinto consider growing diamonds in the lab? Not for now, Ms Kaufman says.

"De Beers are a much bigger producer of diamonds than we are, particularly with Argyle closing," she says.

"I think there is going to be a different definition going forward [about] what's acceptable and what's available on the market.

Growing demand for authenticity testing

The rise of synthetics is yet another reason why people are keen to find out whether their diamonds are the real thing.

Since opening his laboratory in Perth, Mr Chapman has been sent diamonds from people all over the world for testing and certification.

Some of the precious stones, he suspects, may well have interesting stories attached.

"On occasions, quite a nice diamond, a pink diamond, comes through the lab," he says.

"And you think, 'Why has it not been laser engraved by Argyle?'

"But there's also that possibility that it is one of the pink diamonds that are believed to have been taken from the mine under peculiar circumstances and found its way to the market."

Listen to the Expanse: Pink Diamond Heist podcast.