As Argyle gradually transitions into its second life as an underground mine, Rio has been increasing the connections between its star diamond producer and its titanic customer base on the Asian subcontinent.

Celebrating the 25th anniversary of its Mumbai office last month, the mining giant's diamond division upped its commercial profile in the country just as a strengthening rupee seemed to be underpinning a growing market.

"Twenty-five years ago, very few people would have predicted that India would become the powerhouse of the diamond industry," Rio Diamonds managing director Jean-Marc Lieberherr said.

"We are so proud of being part of the journey and we are excited to look to a future that encompasses many opportunities for the Indian diamond industry, from the mine to the market."

This bringing together of mine and market has been more than a sales pitch or a vague boardroom concept for Rio.

Earlier this year, Argyle rolled out the red carpet for 20 of India's leading jewellery companies, hosting the group's first ever visit to see the mine's rebirth as an underground operation firsthand.

"India is the powerhouse of the global diamond industry and an important consumer market for Argyle diamonds," Argyle managing director Shane Johnson said.

"Rio Tinto is delighted to welcome these companies who are developing the Indian market for Argyle diamonds in new and exciting ways."

The transition the delegation witnessed was marked by the latest block caving technology, an annual production rate expected to come in at 20 million carats and an extended mine life to at least 2020.

Officially launched in April last year, the $2.2 billion expansion remains on track, with the installation of a second crusher and ramped up underground production.

Total output in the first half of 2014 was down 4% from a year ago at 4920ct but it was achieved from 58% less processed ore, reflecting the move away from open pit operations.

Ore is delivered by haul truck to a plant able to process 11 million tonnes per annum.

Rio touts the mine's processing as the most efficient in the world, with a procedure that dumps 2500t in the crusher every hour before scrubbing, screening, separation and concentrate recovery via custom-designed x-ray sorters.

The sensors in the sorting process detect diamond fluorescence within the bulk material and send signals to a microprocessor that fires an air blaster valve, blowing the precious minerals into a collection box.

The Indian visit to the operation was followed by the launch last month of a line of diamond collections at the Mumbai office under Rio's Indian marketing initiative Nazraana.

The success of Nazraana is a good measuring stick for the emergence of India's dominance in the global diamond space and the unique reputation of the Argyle brand.

In recent years, the campaign has signed on superstar Bollywood actresses as brand ambassadors while promoting products that tie Indian traditions and designs with the world's leading producer of the coveted pink diamond.

And although the Indian marketing push focuses on gift-giving of lower-cost jewels, the implied connections to Argyle's glamorous rarities are palpable as the mine rolls out its 2014 tender, boasting a record four rare fancy red diamonds.

This month's tender celebrates the 30th anniversary of the sale and has attracted the likes of Japanese first lady Akie Abe at the invitation of the WA government.

"Decades ago, no one would have believed that Australia held the secret of diamonds, let alone virtually the world's entire source of rare pink and red diamonds," Lieberherr said.

"The pinnacle of the production from Rio Tinto's Argyle mine - the annual pink tender diamonds - are now celebrated internationally as amongst the rarest and most valuable diamonds in the world.

"We have seen and continue to see sustained demand and price growth for Argyle pink diamonds."

While sales of pink diamonds to Japan obviously won't be enough to keep the shovels digging at Argyle over the next five years, the twinkle they lend to the Nazraana campaign in India may just do the trick.