Surface coatings can blacken gold or give it a brownish colour, both of which are popular trends now.

Pure gold (99.9 per cent) is 24 carats and is called chuk kam in Cantonese. Although vibrant demand exists in Asia for chuk kam jewellery because it holds its value, alloyed gold is more traditionally seen in western-style jewellery. Typical gold alloys include 18-carat (75 per cent gold), 14-carat (58.5 per cent) and 12-carat (50 per cent) jewellery.

'Gold jewellery is a way of displaying wealth. It makes you feel good and look good,' said Albert Cheng, Far East managing director for the World Gold Council, the marketing arm of the gold-mining industry.

While jewellery accounts for the majority of gold demand, it is a versatile metal with applications in industry, medicine, dentistry and even food.

Edible gold has been featured in culinary creations for centuries. About 12 tonnes of gold are eaten every year in India, much of it on pastries offered as gifts for special occasions.

Shavings of gold leaf are served on chocolates, cocktails, coffees, soups, salads and entrees in fine restaurants from Europe to Japan.

DeLafee, a Swiss company that makes chocolate, lollipops, wine and cigars that contain edible gold, produces what might be considered the ultimate in rich food.

Chocolates sprinkled with flakes of 24-carat gold are the company's best-seller.

Company founder Sebastien Jeanneret said: 'On each chocolate there is about the same quantity of gold as on a gold-plated watch, about 20mg. Gold is used for its aesthetic and symbolic qualities. It's a stable metal, so it is not altered by body fluids,' he said. The metal is inert and does not accumulate inside the body and, alas, passes through essentially undigested. Mr Jeanneret said gold had no taste but its consistency was felt when eaten. He added that the use of gold as a colouring additive was allowed in the European Union and Switzerland. The United States Food and Drug Administration said the agency had 'not made a determination regarding edible gold'.

In other fields, gold-based treatments have been used for decades to reduce the stiffness and pain of rheumatoid arthritis. Gold nanoparticles have been used to deliver cancer-fighting drugs. Gold's biocompatibility and high degree of resistance to bacterial colonisation have made it the preferred material for implants where infection is a potential risk, such as the inner ear. In dentistry, gold fillings, gold inlays, crowns and bridges, and tooth restorations fashioned from gold have a long and highly regarded history.

Gold has been used as a lubricant in engineering applications and as a coating in building glazing because it can reflect heat radiation, thus keeping buildings cooler in summer and warmer in winter.

The emerging field of gold nanotechnology offers the prospect of exciting new developments, including gold nanowires in future electronic devices, nanoparticulate gold catalysts for pollution control and chemical synthesis, and decorative coatings using gold nanoparticles.

An estimated 145,000 tonnes of gold have been mined through the ages, with producers maintaining reserves of about 22,000 tonnes, or about 14 years' worth of production at 2005's production level.

Will gold run out some day, like oil? According to the World Gold Council that's not expected to happen any time soon. The amount of gold has remained fairly constant over time, with new sources being discovered as old deposits are depleted.

Mr Cheng said: 'Unlike oil, which is consumed, gold can always be melted down and recycled.'

But he predicted that the price of gold would continue to rise because of growing demand for gold jewellery from developing markets, such as China and India, the lack of significant new discoveries of gold deposits in recent years and the large stores of gold reserves held by central banks.