Question: What precious metal does Outpost Island Mine and Hedley Mascot Mine have in common?
Sentence (from "Hedley Mascot Mine"): The Hedley Mascot Mine operated between 1936 and 1949 and was one of the most unusual mining operations in the world, being built entirely on the side of a mountain, 5,000 feet above the town of Hedley or seven thousand feet above sea level.
Relevant evidence: No