In the 1930s, a young geologist named Arthur Sorenson mapped the Star Mine in Idaho's Silver Valley, recording his findings on linen paper. The result was page after page of meticulous drawings, each showing different levels of the 8,000-foot mine. "What the geologist had to work with in the past was these flat maps," said Art Smith, a geologist at Hecla Mining Co., gently handling the yellowing pages.