JAPAN has found a large deposit of rare earth minerals in its Pacific seabed, enough to supply its hi-tech industries for more than 200 years, a scientist says.

Around 6.8 million tonnes of the valuable minerals, used in electric cars, iPods and lasers, are sitting under the seabed near a far eastern Japanese island, Tokyo University professor Yasuhiro Kato told AFP on Friday.

He said mud samples taken from an area near Minamitorishima island, some 2000 kilometres southeast of Tokyo, indicated deposits amounted to around 220 times the average annual amount used by industry in Japan.

The seabed contained a substantial amount of dysprosium - a rare earth mineral used in the engines for hybrid cars, he said.

"Specifically on dysprosium, I estimate at least 400 years worth of Japan's current consumption is in the deposits," said the professor, who examined mud samples taken from the seabed around 5600 metres.

"We can start drilling in the mud, using oil extraction technology, within three years at the earliest and start producing rare earth minerals within five years," he said.

The find would be the first time large scale rare-earth deposits had been discovered inside Japan's exclusive economic zone, local media said.

Rare earths are used to make a wide range of high tech products, including powerful magnets, batteries, LED lights, electric cars, iPods, lasers, wind turbines and missiles.

China currently produces more than 90 per cent of the world's supply of rare earths, but has clamped down on exports of them in a move Beijing says is aimed at protecting its environment and conserving supplies.

Originally published as Japan finds major rare earth deposits