As Rio Tinto celebrates the thirtieth year of the iconic Argyle Pink Diamonds Tender, we take a look behind the scenes at the people and processes giving shape to some of the world’s rarest and most precious gems.

Many thousands of miles from the world’s diamond manufacturing hubs, a master diamond polisher sits silent and still, his eyes narrowed in concentration, his senses on high alert. As he “feels” the story of the precious stone on the polishing wheel before him, his colleagues around him are quiet too, respectful of the important connections he is making with the diamond and the significant task he has in front of him.

The intensity of his focus is well justified, for this is no ordinary job and no ordinary workplace. He and his small team of colleagues at Argyle Diamonds’ state-of-the-art manufacturing facility in Perth, Western Australia are the only people entrusted to work on the rarest-of-rare of Argyle’s pink diamonds.

Here, they combine their technical and intuitive skills to shape the magnificent gems that will appear in the exclusive annual Argyle Pink Diamonds Tender: highly coveted gems that fetch often record-breaking prices and will be cherished by many as works of art.

Their work is extremely precise, constantly challenging and, at times, stressful: misjudgments on the polishing wheel can reduce a pink diamond’s significant earning potential.

Thankfully, the job is also very rewarding, often enthralling, and the team are well practised at breaking the tension with music and banter – and even the odd burst of karaoke.

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Argyle pink diamonds in the rough.

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Expert diamond polishers, Richard How Kim Kam and David Burger assessing the rough diamond in the Argyle Pink Diamond facility.

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The polisher brillianteers each intricate facet of the Argyle pink diamond to bring out the most intense hues.

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The complicated lattice structure of pink diamonds is highly unique, making them extremely difficult to polish.

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The diameter of a part-processed Argyle pink diamond is measured using a caliper.

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Expert diamond polisher Richard How Kim Kam at the Argyle Diamonds’ state-of-the-art manufacturing facility in Perth, Western Australia.

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Expert diamond polishers, David Burger and Richard How Kim Kam assessing a rough diamond in the Argyle Pink Diamond facility.

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A diamond on the polishing wheel.

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Once the transformation is complete, the gem will be officially colour-graded by the Gemological Institute of America.

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In addition to the rare pinks and reds, the Argyle mine also produces a small number of blue diamonds.

“The complicated structure of the Argyle pink diamonds means that they can take three to four times longer to polish than white diamonds. Recent advancements in technology are assisting us, especially in the early stages of the process, but there is still heavy dependence on the highly trained eye.”

The rough gems arrive at the Perth facility from the Argyle mine via a trip to Rio Tinto Diamonds’ sales and marketing hub in Antwerp, Belgium, where they are initially separated from the rest of the Argyle production and valued.

In Perth, the potential of each diamond must be carefully assessed. In the past this was done by the collective skills and experience of the diamond planner and polisher, using industry-standard magnification equipment and laser sawing technology.

In the last two years, new technology − the Galaxy 1000 system − has been introduced into the process. This scans the internal features of the gem with 100 per cent accuracy, generating a 3D model of the rough stone that the team can use to confidently plan its cutting and polishing approach.

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The 30th annual Argyle Pink Diamonds Tender (pictured) comprised 54 diamonds of the finest rare red and pink diamonds unearthed from the Argyle Diamond Mine.

Precision and intuition

With the scan of the rough diamond in hand, the next important step is to “chase the colour” a description that refers to polishing a small window on the surface of the diamond to locate the concentrations of colour that will need to be brought out in the polishing process.

One of the unique features of Argyle pink diamonds is the distinct colour zones that appear variously throughout the crystal lattice structure. On closer inspection, this colour is confined to fine, parallel planes.

Once they have agreed on the best shape for maximising both the colour and size of the stone – with enthusiastic discussion about what the final colour grading could be – the plans are passed into the safe and experienced hands of rough preparation technician, Stuart Monkhouse. He readies the specialist cutting equipment that will give recognisable shape to the rough stone, calibrated to the micron level of detail.

Although technology is fundamental, often there's no replacement for experience and a keen eye

Stuart Monkhouse, rough preparation technician

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The process uses both modern technology and magnifying and clasping tools that have been used for decades.

“The complicated lattice structure of pink diamonds is highly unique, making them extremely difficult to polish,” explains Stuart, who has accumulated 15 years of experience with Argyle in this precision role.

“They are like knotted wood. In comparison, cutting white diamonds is like cutting through butter. The decisions made at this stage can have a dramatic impact on the polished stone.

“Although technology is fundamental, often there’s no replacement for experience and a keen eye. The cutting and polishing process is ultimately a human one, where experience, concentration and dedication are key.”

Value in their hands

Argyle’s three master polishers – David Burger, Richard How Kim Kam and Richard Visenjoux – have these qualities in spades if the global excitement surrounding the annual pink tender is anything to go by. Recruited decades ago from South Africa and Mauritius, they have almost 100 years’ combined experience and have polished almost every Argyle pink diamond in the tender’s history.

To do their job well, the polishers require an understanding of the physics of light – how light paths move through the pink diamond and how the flat faces (facets) they create on its surface during the process of “brillianteering” can vary the colour result.

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A selection of Argyle Pink Diamonds Tender stones.

Unleashing the brightness, fire and scintillation of a stone during brillianteering draws on experience, judgment and a close alliance with the stone together with important technical data – with potentially millions of dollars on the line.

These modern-day alchemists ply their craft on the diamond polishing wheel using magnifying and clasping tools that have been used by the industry for decades. Their skill is both that of the artisan and the artist.

Once the transformation is complete, the gem will be officially colour-graded in Perth using an internationally recognised grading system developed by Rio Tinto in the 1990s, to describe the unique colour properties of its gems. This recognises the overall hue of the stone (as colours can range from faint pink through to vivid red and violet blue) and the intensity of the diamond’s colour within that hue.

It is then forwarded onto the Gemological Institute of America, the recognised global experts in diamond gradings, for certification.

According to Shauna, this is a significant moment for the team: “It’s not uncommon to see the team celebrate when a diamond has completed its journey, and marvel at another piece of history being born.”

Thirty years on, the magic of Argyle’s most precious pinks shows no signs of diminishing; indeed, as the yield from the mine diminishes, the gems are becoming more valuable – and more valued – than ever. Argyle is very fortunate to have such a skilled and dedicated group of individuals steering the destiny of these amazing gems, making sure they are the absolute best they can be.