The Henderson molybdenum mine is a large underground

molybdenum Molybdenum is a chemical element with the symbol Mo and atomic number 42 which is located in period 5 and group 6. The name is from Neo-Latin ''molybdaenum'', which is based on Ancient Greek ', meaning lead, since its ores were confused with lea ...

mine west of the town of

Empire An empire is a "political unit" made up of several territories and peoples, "usually created by conquest, and divided between a dominant center and subordinate peripheries". The center of the empire (sometimes referred to as the metropole) ex ...

Clear Creek County, Colorado Clear Creek County is a county located in the U.S. state of Colorado. As of the 2020 census, the population was 9,397. The county seat is Georgetown. Clear Creek County is part of the Denver metropolitan area. History Clear Creek County w ...

, USA. The Henderson mine, which has produced molybdenum since 1976, is owned by

Freeport-McMoRan Freeport-McMoRan Inc., often called Freeport, is an American mining company based in the Freeport-McMoRan Center, in Phoenix, Arizona. The company is the world's largest producer of molybdenum, is a major copper producer and operates the world's ...

. 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.

History

The Henderson mine is near the Urad mine, which produced molybdenum from 1914 to the 1960s, before exhausting its orebody. Owner Climax Molybdenum Co. recognized the potential for deeper orebodies in the area, and discovered the Henderson deposit in 1964. The mine was named after mining engineer Robert Henderson. Production began in 1976; on Jan. 4, 2010, workers mined the billionth pound of molybdenum. In 2006, remaining ore reserves were estimated to be 500 million pounds of recoverable molybdenum. It was considered by the

National Science Foundation The National Science Foundation (NSF) is an independent agency of the United States government that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National I ...

as one of the two final candidates for the

Deep Underground Science and Engineering Laboratory The Sanford Underground Research Facility (SURF), or Sanford Lab, is an underground laboratory in Lead, South Dakota. The deepest underground laboratory in the United States, it houses multiple experiments in areas such as dark matter and neutrino ...

, but lost to the Homestake Mine in

South Dakota South Dakota (; Sioux language, Sioux: , ) is a U.S. state in the West North Central states, North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Lakota people, Lakota and Dakota peo ...

Geology

The deposit is a porphyry-type deposit consisting of a stockwork of small veins of

molybdenite Molybdenite is a mineral of molybdenum disulfide, Mo S2. Similar in appearance and feel to graphite, molybdenite has a lubricating effect that is a consequence of its layered structure. The atomic structure consists of a sheet of molybdenum ato ...

rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral ...

porphyries Porphyry ( ) is a textural term for an igneous rock consisting of coarse-grained crystals such as feldspar or quartz dispersed in a fine-grained silicate-rich, generally aphanitic matrix or groundmass. The larger crystals are called phenocr ...

Tertiary Tertiary ( ) is a widely used but obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start ...

age that intrude into

Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the ...

Silver Plume

granite Granite () is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies undergro ...

. The ore averages 0.2% molybdenum. The molybdenite is associated with

pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic Luster (mineralogy), lust ...

and

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical form ...

. The deposit is similar to other porphyry molybdenum deposits such as the

Climax mine The Climax mine, located in Climax, Colorado, United States, is a major molybdenum mine in Lake County, Colorado, Lake and Summit County, Colorado, Summit counties, Colorado. Shipments from the mine began in 1915. At its highest output, the Clima ...

in Colorado and the Questa mine in

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ker ...

. The Henderson deposit is located in the

Colorado Mineral Belt The Colorado Mineral Belt (CMB) is an area of ore deposits from the La Plata Mountains in Southwestern Colorado to near the middle of the state at Boulder, Colorado and from which over 25 million troy ounces (778 t) of gold were extracted begin ...

, a northeast-southwest alignment of metal deposits that crosses the mountainous part of Colorado from

Boulder In geology, a boulder (or rarely bowlder) is a rock fragment with size greater than in diameter. Smaller pieces are called cobbles and pebbles. While a boulder may be small enough to move or roll manually, others are extremely massive. In c ...

Durango Durango (), officially named Estado Libre y Soberano de Durango ( en, Free and Sovereign State of Durango; Tepehuán: ''Korian''; Nahuatl: ''Tepēhuahcān''), is one of the 31 states which make up the 32 Federal Entities of Mexico, situated in ...

Mining

Mining is done by

block caving Underground hard-rock mining refers to various underground mining techniques used to excavate "hard" minerals, usually those containing metals, such as ore containing gold, silver, iron, copper, zinc, nickel, tin, and lead. It also involves th ...

. In 1980 the cavity produced by the panel caving broke through to the surface, producing a large

glory hole A glory hole (also spelled gloryhole and glory-hole) is a hole in a wall or partition, often between public toilet, public lavatory cubicles or adult video arcade, sex video arcade booths and lounges, for people to engage in sexual activity or ...

(subsidence) on the side of Red Mountain. The ore is carried by a conveyor belt system extending through a tunnel beneath the

Continental Divide A continental divide is a drainage divide on a continent such that the drainage basin on one side of the divide feeds into one ocean or sea, and the basin on the other side either feeds into a different ocean or sea, or else is endorheic, not ...

and then overland to the ore processing mill near Parshall, Colorado. The ore is treated by

froth flotation Froth flotation is a process for selectively separating hydrophobic materials from hydrophilic. This is used in mineral processing, paper recycling and waste-water treatment industries. Historically this was first used in the mining industry, wher ...

to obtain molybdenite concentrate, which is shipped to a plant in

Fort Madison, Iowa Fort Madison is a city and a county seat of Lee County, Iowa, United States along with Keokuk. Of Iowa's 99 counties, Lee County is the only one with two county seats. The population was 10,270 at the time of the 2020 census. Located along the ...

for further processing. Prior to August 1999, ore was hauled on a

narrow gauge A narrow-gauge railway (narrow-gauge railroad in the US) is a railway with a track gauge narrower than standard . Most narrow-gauge railways are between and . Since narrow-gauge railways are usually built with tighter curves, smaller structu ...

railroad Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are incorporated in tracks. In contrast to road transport, where the vehicles run on a pre ...

double-tracked Double tracking or doubling is an audio recording technique in which a performer sings or plays along with their own prerecorded performance, usually to produce a stronger or bigger sound than can be obtained with a single voice or instrument. ...

and

electrified Electrification is the process of powering by electricity and, in many contexts, the introduction of such power by changing over from an earlier power source. The broad meaning of the term, such as in the history of technology, economic history ...

at 1,400 V DC, except in the ore loading area, where 600 V DC was used. 4-wheel

locomotives A locomotive or engine is a rail transport vehicle that provides the motive power for a train. If a locomotive is capable of carrying a payload, it is usually rather referred to as a multiple unit, motor coach, railcar or power car; the u ...

weighing hauled trains of 4-wheel

ore car In US railroad terminology, a gondola is an open-topped rail vehicle used for transporting loose bulk materials. Because of their low side walls, gondolas are also suitable for the carriage of such high-density cargos as steel plates or coils, ...

s. A typical train of 20 to 25 cars required 3 locomotives, two pulling and one pushing up the long 3-percent

grade Grade most commonly refers to: * Grade (education), a measurement of a student's performance * Grade, the number of the year a student has reached in a given educational stage * Grade (slope), the steepness of a slope Grade or grading may also ref ...

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, 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 for maintenance access.Chris Nuthall
Henderson Mine Railroad
May 19, 2011.

Location

The Henderson mine is located at at an elevation of about 10,300 feet, about 1.6 miles east of the Continental Divide. It is approximately 9 miles west of Empire, Colorado. The haulage tunnel portal is located at . The mill is located at .

Outdoor recreation

The Henderson mine is on private land. However, the mine is surrounded by

US Forest Service The United States Forest Service (USFS) is an agency of the U.S. Department of Agriculture that administers the nation's 154 national forests and 20 national grasslands. The Forest Service manages of land. Major divisions of the agency inc ...

land of the

Arapaho National Forest Arapaho National Forest is a National Forest located in north-central Colorado, United States. The region is managed jointly with the Roosevelt National Forest and the Pawnee National Grassland from the United States Forest Service office in ...

. There is a public parking lot on the Jones Pass Road near the mine, and the National Forest land near the mine is popular year-round for hiking, cross-country skiing, and snowshoeing.

References

External links

Freeport-McMoRan website: ''Henderson mine''
(dead link 10 February 2017)
"Henderson Produces Billionth Pound of Molybdenum"
January 4, 2010 {{DEFAULTSORT:Henderson Molybdenum Mine Buildings and structures in Clear Creek County, Colorado Mines in Colorado Underground mines in the United States Molybdenum mines in the United States Freeport-McMoRan mines 1976 establishments in Colorado 3 ft 6 in gauge railways in the United States