JAPAN has the biggest "urban mine" in the world as a tremendous amount of gold, silver and other recyclable rare metals lies in its home appliances, according to a research institute.

Japan, which has few natural resources, owns about 6,800 tonnes of gold and 60,000 tonnes of silver, which work out to 16 per cent and 22 per cent respectively of the world's known deposits of these metals, said the National Institute for Materials Science (NIMS) in Tsukuba, 50km north-east of Tokyo, on Saturday.

The gold and silver amounts also surpass the total deposits in any other country, reported the Yomiuri Shimbun, which estimated that Japan's "goldmine" is worth 20 trillion yen (S$263 billion).

Furthermore, Japan's "stockpile" of indium, used to make liquid crystals, works out to around 61 per cent of global deposits, Kyodo news agency quoted the NIMS as saying.

"While many products with these materials are usually transferred overseas as post-consumer waste, we would like to study how to use these potential resources," an official from the institute said.

The NIMS used government trade statistics in Japan's first-ever exercise in quantifying the rare metals - 20 types in all - concealed in home appliances in the country.

It did its calculations by subtracting the amount exported - including spare parts - from the amount imported.

Rare metals in home appliances still being manufactured or in use, as well as those in discarded products, were also included.

As the world's metal resources are being depleted, Japan should turn to mining its hidden "mineral lode" through efficient, low-cost recycling methods, the NIMS said.

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