It's never been easy to make a living in Libby, Mont. Citizens in this town of 12,000, tucked into the dense, damp conifer forests of northwestern Montana, have long scraped by on seasonal logging jobs and other sporadic work. So in the 1920s, when local entrepreneur Edward Alley discovered that a nearby vermiculite deposit yielded an efficient, lightweight insulation and fireproofing material, Libbyites were thrilled.