An announcement by the Bush administration yesterday that it would repeal a Clinton-era mining regulation pleased industry leaders but angered environmentalists. The regulation, which applies to hard-rock minerals such as gold, silver, and copper, allows the Interior secretary to veto new mines on federal lands if they threaten the well-being of communities or the environment. In the last five years, mining development has declined 85 percent, a fact industry leaders blame on the Clinton administration’s policies. Environmentalists, however, say the hard-rock mining regulation is necessary to prevent groundwater pollution; they plan to sue to stop the repeal.