So Shirley Bassey lied, diamonds are not forever - at least not for BHP Billiton, the world's biggest mining company.
Commodities: the long-term future is bright for diamonds
BHP's move is more simply a recognition of the fact that it will be hard to scale up diamond mining.
The miner said last Tuesday that it was reviewing its diamond business, with an eye to selling off some or all of these assets. The problem? Diamond mines seem not to fit within its strategy of investing in "large, long life" assets that have potential for expansion.
The news came after the Oppenheimer dynasty last month exited the diamond industry, ending decades of involvement as the family finally agreed to hand over control of producer De Beers to mining giant Anglo American.
On top of this, rough diamond prices have been on a downwards path in recent months. Pricing is complex with no single market, but indices show that after recovering strongly from the crash during the depth of the financial crisis, prices have softened markedly from their June 2011 highs as fears for the global economy have risen.
So do these developments signal that the rocks have lost some of their sparkle? Not quite.
BHP's move is more simply a recognition of the fact that it will be hard to scale up diamond mining, while the Oppenheimers' exit can be more accurately read as a sign of confidence in the fundamentals of the industry from Anglo.
Prices are still nowhere near the troughs of recent years – diamonds have been among the best performing commodities of 2011 – and the longer-term outlook looks positive. Petra Diamonds on Friday gave a presentation predicting that worldwide diamond production will remain flat until 2017, against a backdrop of growing demand.
A "significant" gap between supply and demand will emerge, it believes. Many of the world's major diamond mines are in decline, yet no major sites have been discovered since the 1990s.
Against this backdrop Tiffany & Co, the jewellers, and watchmaker Swatch are both said to be investigating ways to secure their rough diamond supply.
Who is driving this market? India and China, unsurprisingly, as the world's economic power keeps shifting to the rapidly growing East.
Although the US is still the largest market for diamonds, it cannot be too long before it will be overtaken by China – and in a flurry of confetti. Only 15 years ago, there was virtually no culture of diamond engagement rings, while today more than half the brides in Beijing and Shanghai receive them, according to Anglo American.
Meanwhile in India, demand is so high that in a Mumbai mall one company has opened the first of its planned ATM machines selling diamond jewellery and gold coins. As emerging markets urbanise further, the world is expected to add another 800m middle-income consumers by 2030 – with half of these big spenders in China and India.
That is why Graff, the London jewellers, is preparing to list in Hong Kong, a move seen as being as much about raising its profile in an increasingly important market as it is about raising funds. Similarly Chow Tai Fook, Chinese diamond retailer, is preparing for what may be Hong Kong's biggest initial public offering this year.
Should this all sound as if diamonds are becoming increasingly democratised, Petra predicts that the major beneficiaries of its forecast shortage of rough diamonds will be producers of the big, better quality gems – where supply is tightest. The super-rich do tend to weather a downturn better than anyone, and demand for the shiniest rocks looks particularly healthy.
Diamonds are not without their shorter-term headwinds, however. Volatility will inevitably remain as the eurozone crisis drags on, while a slowdown in China would hit sales. And, like the wider mining sector, the diamond industry faces the increasing headache of resource nationalism, whereby governments make moves to enjoy a bigger share of the riches dug out of their lands. Just last week, it emerged that Zimbabwe is planning to raise the fees charged to mine diamonds.
Still, in the long term, the future looks bright for diamonds. Sparkling, you could say.
• Platinum prices are set to be boosted by the needs of the recovering auto sector and rising investment demand, according to consultancy GFMS.
It sees prices strengthening as high as $1,800 (£1,154) next year, even as supply hits a five-year peak. Spot platinum is down 12pc so far this year, bumping around $1,550 an ounce. There is an upside for some – the shrinking cost gap with gold means that people who would have defaulted to a white gold engagement ring are trading up to platinum.