a gate to the Climax Mine, north of Leadville.
Wikipedia says: "The Climax mine, located in Climax, Colorado, is a major molybdenum mine in Lake and Summit counties. Shipments from the mine began in 1915. At its highest output, the Climax mine was the largest molybdenum mine in the world, and for many years it supplied three-fourths of the world's supply of molybdenum.
"After a long shutdown, the Climax mine has reopened and resumed shipment of molybdenum on May 10, 2012.
"The ability of molybdenum to withstand extreme temperatures without significantly expanding or softening makes it useful in applications that involve intense heat, including the manufacture of armor, aircraft parts, electrical contacts, industrial motors and filaments."