Japan could soon join the list of the world's top mineral producers. All it needs to do is recover the gold, silver, and platinum tossed into its landfills. The source of this bounty? The 600,000 tons of electronic appliances thrown away each year. According to a study by the National Institute for Materials Science in Tsukuba, Japanese landfills -- think of them as urban mines -- hold three times as much gold and silver and six times as much platinum as the world consumes each year.