After a decade-long struggle, 13 Native American tribes and the Sierra Club have finally succeeded in closing down a strip mine in Arizona that supplied much of the pumice used around the world to make stonewashed denim. Federal officials and the mining company signed an agreement yesterday to shut down the mining operation within six months. Mine opponents said the operation damaged the environment in an area considered sacred by Native Americans, and for the frivolous purpose of making jeans look worn. “You should have to work to get that look,” said Andrew Bessler of the Sierra Club.