page_title: Henderson molybdenum mine
section_title: Mining
hierarchical_section_title: Henderson molybdenum mine / Mining
caption_attribution_description: English: Glory hole at the Henderson molybdenum mine, Clear Creek County, USA
context_page_description: The Henderson molybdenum mine is a large underground molybdenum mine west of the town of Empire in Clear Creek County, Colorado, USA. The Henderson mine, which has produced molybdenum since 1976, is owned by Freeport-McMoRan.
  The Henderson mine is North America's largest producer of primary molybdenum. 2007 production was 40 million pounds of molybdenum, with a value of $1.1 billion.
context_section_description: Mining is done by block caving.  In 1980 the cavity produced by the panel caving broke through to the surface, producing a large glory hole (subsidence) on the side of Red Mountain. 
  The ore is carried by a 15-mile (24 km) conveyor belt system extending through a 10-mile (16 km) tunnel beneath the Continental Divide  and then five miles (8 km) overland to the ore processing mill near Parshall, Colorado.  The ore is treated by froth flotation to obtain molybdenite concentrate, which is shipped to a plant in Fort Madison, Iowa for further processing.
  Prior to August 1999, ore was hauled on a 3 ft 6 in (1,067 mm) narrow gauge railroad, double-tracked and electrified at 1,400 V DC, except in the ore loading area, where 600 V DC was used.  4-wheel locomotives weighing 55–62 short tons (49–55 long tons; 50–56 metric tons) hauled trains of 4-wheel 20-short-ton (17.9-long-ton; 18.1-metric-ton) ore cars.  A typical train of 20 to 25 cars required 3 locomotives, two pulling and one pushing up the long 3-percent grade in the tunnel.  After 1996, train operation was fully automated.  Rail haulage was abandoned when the ore above the rail level in the mine was exhausted.  The new working level of the mine, 400 feet (122 m) below the rail level, required a conveyor to lift the ore to the haulage tunnel, and it was eventually decided to extend this conveyor the full distance to the mill.  Within the tunnel, one of the two tracks remains available maintenance access.
caption: The Henderson mine glory hole, 1989.
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