Diamond price forecasts add a rosy tint to mine closures

With few comparable replacements in the pipeline, supply could peak in next 10 years

Miner Rio Tinto unveiled the largest pink diamond from its Argyle mine in Western Australia this summer. The 3.14 carat “Argyle Alpha”, found in 2015, is part of a package of 63 brightly coloured red and violet diamonds shown to potential buyers in Hong Kong this month.

The stones are becoming ever more scarce as the mine, which upended the heavily controlled diamond market when it opened in 1983, is set to come to the end of its life in 2020.

The closure marks a turning point for the diamond market as there are few comparable replacements in the pipeline. Analysts expect the supply of diamonds to peak within the next 10 years, as demand continues to grow.

“Rio Tinto’s Argyle mine is the world’s only source of these highly coveted pink, red and violet diamonds and we expect considerable interest in this year’s collection,” Jean-Sébastien Jacques, Rio Tinto’s chief executive, said in a statement.

“You’re seeing the real significant depletion of the very economic mines” – Paul Zimnisky, Diamond Analytics

He added that the constrained supply will “support significant value appreciation for pink diamonds”. The tender will travel to New York next month, with bids closing on October 10.

Prices for high-quality pink stones have outperformed those of other diamonds over the past decade because of their rarity, according to Paul Zimnisky of Diamond Analytics in New York. He estimates pink stones account for less than 0.01 per cent of the world’s diamonds by volume — the Argyle mine produces close to 90 per cent of these.

The wider diamond market is expected to feel a squeeze, too, however. RBC Capital Markets forecast last year that total supply would increase 4 per cent  to 145m carats this year “before retreating as older mines begin to reach the end of their lives”.