Proof that diamonds are getting harder to find can be seen in the South African bush, where one of the world's largest mining companies is spending USD 2 billion tunnelling beneath a vast open-pit mine.
De Beers spent 25 years digging a 450-metre deep by one-kilometre wide hole to access diamond-rich rock from the surface at the Venetia mine, close to the border with Zimbabwe and Botswana.
Now a whole new underground mine is being constructed underneath the hole to reach diamonds more than 1,000 metres below ground -- a big bet by De Beers that their investment will reap decades of profit.
"We are in very challenging times," Ludwig Von Maltitz, the mine's general manager, told AFP on the edge of the cavernous open-pit as trucks rumbled up to the processing plant.
"Worldwide, the easier diamond sources have probably been found but, with this resource here, we hope we have something that can extend well into the future."
As the hunt for diamonds becomes tougher, mining companies must go to greater lengths -- and absorb higher costs -- to secure the ultimate precious stone and symbol of love.
"Across the globe, the big diamond deposits have been exploited, and I don't see any big new mines coming online," Peter Major, mining specialist at Johannesburg-based Cadiz Solutions, told AFP.
"We are often told that the growing world population, combined with the increasing difficulty of finding diamonds, will mean prices always rise, but we will see. Many producers are losing money.
"The project at Venetia is stupendous -- especially as very few other firms are investing in mining in South Africa."
Demand for diamonds over the last decade has been driven by a new generation of buyers in China and India that have adopted the tradition of giving diamond engagement rings.
Latest figures suggest that such new markets are fragile.
De Beers last month reported that global demand for diamond jewellery grew two per cent in 2015 with growth strongest in the United States and China.
But a dip in India and across the Gulf region pointed to weakening growth in many emerging markets.
"China and India drove diamond prices up, along with speculation that the growth rate would continue indefinitely," industry analyst Paul Zimnisky said, speaking from New York.
"People got overly optimistic and greedy," he said.
Zimnisky believes "it is misleading to say we are running out of diamonds" as "when prices rise, mines that were uneconomic become profitable".
However the industry can't react that quickly to a rise in demand and prices.
