What makes pink diamonds pink?

24 December 2014 Last updated at 01:09What makes pink diamonds pink? 

By Jane O'BrienBBC News, Washington

They're one of the world's rarest jewels - but nobody knows for certain why pink diamonds are pink.

That hasn't stopped investors from snapping them up at auction and sending prices skyrocketing. In October a new world record was set at a Sotheby's sale in Hong Kong when an 8.41-carat pink diamond sold for $17,768,041 (£11,438,714) - more than $2.1m (£1.8m) a carat.

"Everybody's talking about them, and everybody loves them," says Jeffrey Post, curator of the National Gem and Mineral Collection at the Smithsonian's National Museum of Natural History in Washington, DC. "Yet you can't tell people why they're pink."

Other diamonds get their colour from chemical impurities that absorb light. Yellow diamonds contain traces of nitrogen, and blue diamonds contain boron. But no similar impurities have been found in pink diamonds, leading scientists to speculate that the colour may be the result of some kind of seismic shock that altered the stone's molecular structure.

It's now hoped that a cache of brown and pink diamonds from the Argyle mine in Western Australia may solve the mystery. The mine, owned by Rio Tinto, is the world's largest source of pink diamonds, even though they're so rare that only a few are produced each year.

As well as revealing what makes them pink, scientists hope that studying the diamonds will tell them more about the history of the planet.

Diamonds are the Earth's messengers, says Post. "They come from a hundred miles below the surface and tell us about a part of the Earth that we can't visit. They're also giving us a peek back in time because most diamonds formed about two to three billion years ago. 

"Each one is a time capsule, and the pink diamonds, because they're different from all the other diamonds, have a different part of the story to tell."

Scientists have already examined the Argyle diamonds using a mass spectrometer to try to find any trace of impurities that may be causing the pink colour. The machine agitates the diamonds and analyses the chemical structure of the atoms that are released. 

"There is no impurity that we've been able to associate so far with the pink colour in diamonds," says Post. "Spectroscopic measurements don't show you any additional features that you can ascribe to a particular colouring agent."

They've also used a focused ion beam to cut a tiny trench in the surface of the diamonds and remove a slither than can be measured under a powerful electron microscope. They've discovered that most pink diamonds are not uniformly pink but have pink zones that alternate with clear areas.

The zones, known as twin planes, were formed by some kind of shock - possibly the result of volcanic activity that propelled the diamonds to the surface or from something that happened to them as they were being formed deep underground.

"The twin plane itself should not give rise to colour," says Post. "But we think when those twin planes form, and slide back and forth, one against the other like a fault plane, that certain kinds of defects formed. The defects give us the pink colour. But what we've not been able to do yet is find the specific kind of defect."

Although pink diamonds are among the most valuable jewels today, 20 years ago they were little more than a geological curiosity. Sales have been driven by savvy marketing and a growing appreciation of their uniqueness.

"It really comes down to the rarity," says Richard Revez, a gem expert at Florida-based Kravit Estate Department. "When you talk about coloured diamonds, they're already in the elite 1% produced in the world. Pink diamonds are the 1% of the 1%."

He says the most sought-after diamonds are actually red, but orange, green, blue and yellow are highly desirable. An orange diamond attracted the highest price paid per carat for any diamond at auction last year, selling for $35m, or $2.4m a carat.

"We've craved diamonds for millennia," says Revez. The first gems were probably discovered on river banks in India, but their existence is recorded in Greek and Roman history. "It was believed there was a vein that ran directly from the heart to the ring finger - that's why we wear (diamonds) on our ring fingers. And Cupid's arrows were tipped with diamonds to pierce the heart easier," he says.

Archduke Maximilian of Austria is believed to have started the tradition of diamond engagement rings among the upper classes when he presented one to Mary of Burgundy in 1477.

But it wasn't until the 1950s that international standards to grade diamonds were set by the Gemological Institute of America (GIA), a classification system that is still used today.

But only science can reveal why pink diamonds are pink.

Pink diamonds can be artificially created, says the Smithsonian's Post. And the only way to tell if it's a synthetic stone is to understand what causes the colour to occur naturally. 

"Then I can tell you for sure that that is a diamond that came out of the earth as opposed to one that came out of somebody's laboratory. It can make the difference of millions of dollars in the value of a single diamond, knowing whether it is a natural pink or not."

What does a man - who makes memorial diamonds - do with his own Mum's ashes?

The answer is - scatter them in paradise.  My own Mum died suddenly whilst I was taking my Yachting exams, I wasn't told she had died until AFTER the exam, so it was a very sad time of both elation to pass the exams but to lose your Mum so unexpectedly.

After the family funeral and as planned - I sailed away to live in the Caribbean for 5 years. The ashes had been under the stairs at my GF's house, but I had asked for them to be brought out to the boat.  Coincidentally, my GF's Mum also died - just a few days before she was due to visit me in the Bahamas.

So, in the end, both have been scattered in Paradise, a gorgeous place called 'Bakers Bay' - just outside Green Turtle Cay in Abaco.

Sadly, at that time, I had no plans to start a new business in the funeral industry so I missed a great opportunity to save 100 grams of ashes with which I could have made my own 'Memorial Diamond' - from my Mums last remnants.

We wish funeral directors would promote UK 'Memorial Diamonds'

Considering we (Phoenix-Diamonds.com) are the only UK based 'Memorial Diamond' maker in the world, you would expect British funeral directors to learn more about Who, What, Why, When, Where and How....... Our competition is Russian, American and European - and that's it!!! Why? Because the equipment runs into ££Millions and the expertise spans many many years (of both failure and successes) so we are not likely to suffer anyone setting up next week.  But there is a difficulty facing all the bereaved left behind who wish to memorialise their loved one - with such huge sums involved (£3250 to £12,500) the industry is bound to have the con's and 'suspect' products..... Already we have had 'Tomorrows Traditions' allegedly conning customers who (in the words of an ex partner...) have supplied diamonds NOT made from the ashes of the loved-one.  It would be simple to buy a man-made diamond of almost flawless quality, throw the ashes away and hand over the cheaper diamond at the more profitable price of a real 'Memorial Diamond'.  Also, colours are suspect and we will tackle this in our next posting........ hold your breath

$35,000 - are you mad??

We've been offered this natural diamond [from] but who on earth would say this a fabulous?? It's described as "Brownish, Reddish, Orange" and they want $35,000 for a Princess cut diamond weighing 0.8 carat...... are they mad??
Our laboratory grown diamonds are canary coloured (light yellow) and they cost £6500 for 1.00 carat cut in 'Brilliant' with 58 facets - AND - they are made from the last remnants of your loved-one's ashes or hair.  A bargain for the Brits........

Champagne and Cognac diamonds - beware!

The terms 'Champagne', 'Cognac' and 'Coffee' refer to different types of brown diamonds. In the diamond processing/dealing industry, the word 'Brown' is considered a killer as far as diamond value goes. Even though champagne is a light yellow colour, champagne diamonds are Light Brown. Cognac is usually used to describe a diamond that is Orangish-Brown because cognac is a deep golden-orange colour.

These are NOT our manufacture (probably Russian)  and NOT 'Canary' in colour

What are Memorial Diamonds?

Memorial diamonds are REAL genuine diamonds made in a laboratory but also made out of the ASHES ('Cremains') or hair of a person or animal - alive or deceased.