It is praised for its culinary and health properties by any cook worth his salt, but long before olive oil made it into the Mediterranean diet Cypriots used it as fuel to melt copper, archaeologists say.

Italian researchers have discovered that environmentally friendly olive oil was used in furnaces at a site in southern Cyprus up to 4,000 years ago, instead of the fume-belching charcoal used in industry for hundreds of years since.

Described as "liquid gold" by the ancient Greek poet Homer, olive oil has long been associated with grooming, pampering and the religious rites of the ancients, but not - at least in the Mediterranean - with heavy industry.

"We know that olive oil made it into our food around 1,000 BC, but it is the first time we have laboratory evidence that it was used in smelting as a fuel," archaeologist Maria Rosaria Belgiorno told Reuters.

Cyprus was famed in antiquity for its copper and is believed to have given its name to the Latin term for the metal, Cuprum.

The find by Belgiorno's team suggested mankind might be returning to its roots, at least in terms of energy.

"It is the first time this has been discovered ... and in Europe it's only recently that industry has turned to biofuels. This oil burns like benzene," Belgiorno said.

Today's Cypriots might, however, think twice about pumping this precious commodity into their petrol tanks instead of drizzling it over their meals.

Average annual production of about 13,500 tones just about meets local demand and olive oil now sells for around $6 per liter, compared to around 55 cents for regular fuel.

DARK MARKS LEFT BY TIME

The smelting site known as Pyrgos Mavroraki is thought to be part of a larger industrial unit dating from 2,000 BC, when Cyprus was in its early to mid bronze age.

Lying some 90 km (60 miles) southwest of the capital Nicosia among sprawling villas, the complex includes copper smelting works, facilities for textile weaving and dyeing, a winery and an olive press.

"The olive press and storage facilities were in the middle of two areas where copper was worked. It shows that for sure they used olive oil. Can you imagine building an olive press in the middle of a metallurgy plant. Why?" said Belgiorno.

Tests carried out by the Italian Institute of Technologies Applied to Cultural Heritage, for whom Belgiorno works, have discovered olive oil residues in ovens on the site.

Belgiorno said researchers were puzzled by the fact that no charcoal -- the fuel most widely used at the time -- was found. Charcoal remains intact despite the passage of time, she said.

"There were no storage areas for charcoal. We have discovered that to melt copper you need five kilos of olive oil, compared to 80 kilos of charcoal."

Dark marks on the hard-packed earth in the complex might escape the untrained eye. But these are stains from the oil used in the furnaces, traces which also do not fade.

CYPRUS, THE FILTER

Belgiorno said metallurgy sites have been found close to olive oil production areas in Egypt and Jordan, so Cypriots could not lay claim to being the first to use biofuels.

It was, however, the first time science had conclusively proven that olive oil was used as a fuel, she said.

The highly prized commodity was a key ingredient of perfumes and ancient geographers noted the abundance of olive groves and copper mines in Cyprus.

"I suspect the technology came from abroad, most probably through contact with Palestine and Jordan," said Belgiorno.

Last year at the same site, Belgiorno's team found what they described as the world's most ancient perfumery, which used olive oil infused with local herbs.

The site's textile dyeing facilities also suggested Cypriots had a fashionable flair with their fabrics, using tiny veins painstakingly extracted from Mediterranean sea snails to dye their clothes indigo.

"Nobody can really speak about prehistory without mentioning Cyprus. It was a filter, it took technology from the Middle East and redistributed it to the western world," said Belgiorno.