Marilyn Monroe was right all along. Diamonds really do appear to be a girl's best friend

They have been fêted as teardrops of the gods, a source of spiritual healing and an eternal symbol of love. But their association with conflicts, exploitation and child labour appeared to have tarnished their reputation in recent years.

But all that appears to have changed. Yesterday, it emerged that demand for diamonds was soaring, prompting a healthy surge for the diamond industry. De Beers, the world's biggest diamond producer, announced yesterday its third increase in the price of rough diamonds in the past six months.

During the first six months of this year, rough diamond sales at De Beers rose by 7 per cent. That compares with a growth of 6 per cent during to the whole of the 1990s.

"Consumer confidence levels have increased and macro economic indicators are broadly positive, indicating that the environment will be in place to support continued growth," said a spokeswoman for the De Beers Group. "All of our research shows that consumers want the real thing: 96 per cent of all adult women in the US want a real diamond.

"It is quite a unique moment for the industry and the market is extremely buoyant," said Dennis Terry, managing director of Dianet, independent experts in diamond valuation.

"It is most certainly a growth in consumer demand in the past six months or so that has led to these price increases.

"All of that reflects consumer confidence levels rising globally and as the prices of rough diamonds rise, polished diamonds will have to follow."

The global diamond market, of which the US makes up half, is currently valued by experts at an estimated $30bn (£16bn). The one constant in the fluctuating world of celebrity has long been their perennial attraction to large diamonds.

From Keira Knightley, who was recently weighed down with £250,000 worth of diamonds at the King Arthur premiere to Jade Jagger, who has stamped her personalised bling style on the urban diamond wearer, celebrities have long been drawn to their sparkle.

Ethical consumers, however, are another matter. The 20 per cent drop in European sales over the past 10 years has been attributed at least in part to the diamond's association with political conflict.

Diamonds have been exposed as fuelling conflict around the world, particularly in areas such as Angola and Sierra Leone, where illicit transaction of rough diamonds have been found to have funded arms for warring factions.

However, high-profile steps have recently been taken by the industry to create a more ethical diamond trade. Two months ago, it was agreed that a new "fairtrade" logo would be introduced to reassure consumers fearful of feeding the trade in so-called "blood diamonds".

Today, the diamond market is enjoying a healthy resurgence, according to Charles Kernot, analyst at Seymour Pierce. "The price rises at De Beers are related to both an increase in consumer demand and a drop in worldwide production levels," he said.

While the impact of price increases is expected to be negligible for the British consumer, because of the weakness of the dollar, jewellers acknowledged the current surge in demand. "People within the industry may grumble and groan about the price rises but most jewellers are taking it on the chin," said Harry Levy, deputy chairman of the British Jewellers' Association, which represents 600 companies in the jewellery manufacturing industry.

"This is probably because there seems to be an increase in demand from consumers, certainly in the Far East."

For the jewellers covering the Hatton Garden area of London, there was the feeling that the eternal attraction of the sparkle of the diamond was likely to compensate for rises in cost from suppliers.

"It is quite unusual for so many price rises and it will push prices up but it's not really cause for concern," said Adam Gray, manager at Anthony Gray jewellers, which specialises in diamond rings.

"There has been more demand for but it's been more fashion-led pieces, such as men's jewellery, rather than traditional engagement rings."

CUTTING EDGE

* Diamonds are the hardest natural substance on earth

* The ancient Greeks believed they were the tears of the gods

* The first diamonds were mined in India more than 4,000 years ago

* Louis IX of France made a law reserving diamonds for kings

* Botswana, Russia, South Africa, Angola, Namibia, Australia and the Democratic Republic of Congo are the top seven diamond-producing countries, accounting for 80 per cent of the world's rough diamond supply

* Diamonds are believed to have been formed more than 100 miles beneath the surface of the earth and shot to the surface by volcanoes

* The largest rough diamond found was the 3,106 carat Cullinan, which was discovered in South Africa in 1905

* Pink diamonds are the world's rarest diamonds, fetching up to £550,000 per carat when sold