Cortez Gold Mine
Encyclopedia
Cortez Gold Mine is a large gold
mining
and processing
facility in Lander
and Eureka County
, Nevada
, United States
, located approximately 75 miles (120.7 km) southwest of Elko
. It is owned and operated by Barrick Gold
and is made up of the Pipeline and South Pipeline deposits and the Cortez Hills deposit. The Pipeline and South Pipeline are open pit
mines, and the Cortez Hills deposit, currently under construction will utilize both underground and open pit mining techniques. Under continuous operation, Cortez has been open longer than any gold mine in the state of Nevada. It will become Barrick's largest gold producer in Nevada, in part because of the decline in production from their Goldstrike mine
and the development of the Cortez Hills deposit.
The Cortez Mountains
has been mined since 1862, with silver
being the primary commodity the 1940s. The Gold Acres operation in the Cortez Mountains included open pit and underground mines in the 1930s and 1940s. Cortez Gold opened in 1968 and production ended in 1976. The United States Bureau of Mines
built a pilot plant
in 1969 which would made heap leaching
for gold in commercially viable by 1971. The low grade ore
and dump material from the Gold Acres operation was then heap leached. The Cortez mill
was reopened as the price of gold increased in the early 1980s, feed for the mill was provided by the nearby Horse Canyon deposit between 1983 and 1987. Further exploration of the region was carried out by Cortez Joint Venture which involved Placer Dome
and Kenecott
( at the time Kenecott was a BP Minerals
subsidiary
). The result of the joint venture's exploration was the 1991 discovery of the Pipeline orebody. The Pipeline orebody was located near the Gold Acres operation, instead of being located in the foothills, it was entirely within the Crescent Valley. The Pipeline orebody was much larger than the original orebodies in the region. The entire Pipeline complex contained 23 million ounces of gold between the original orebodies, the Pipeline orebody and the later discoveries of South Pipeline, Crossroads and Gap. The Cortez Joint Venture built the Pipeline Mine and mill in early 1996 following a series of ownership disputes with junior mining companies. Commissioning of the Pipeline mine cost US$
250 million, and resulted an annual output between 1998 and 2005 of over one million ounces of gold per year. The Cortez Hills deposit was discovered in 2002, underground development to define the resource limits began in 2006. Barrick Gold acquired 60% in Cortez in 2006 when it purchased Placer Dome for US$10.4 billion, and acquired the remaining 40% from Rio Tinto
in March 2008 for US$1.7 billion.
and Cortez Mountains
, a basin in the traditional Basin and Range
setting of Nevada
. Precious metal
mineralization
came during Jurassic
-Miocene
periods. The Pipeline complex lies within 600 feet (183 m) of silt
y limestone
in what is called the Silurian
Roberts Mountain Formation. Above this is Devonian
Wenban Limestone, which acts as the host rock of the Cortez Hills deposit. Above the Devonian Limestone is Quaternary
alluvium
.
The Pipeline and South Pipeline deposits are currently being mined using traditional open pit mining techniques, while the Cortez Hills deposit will be mined out using both open pit and underground mining techniques.
of 3:1. Ore in the open pit mines is hauled on surface using 400 short tons (362.9 t) Liebherr
T282B
trucks
. Cortez currently owns 24 T282Bs, which accounts for 10% of the total sales of T282 & T282B trucks worldwide.
to surface and to provide ventilation
for the mining operation. The declines are accessed via portals
on the wall of an old open pit, the haulage (west) decline brings fresh air into the mine and the east decline exhausts air to surface.
The declines and lateral development utilize welded wire mesh and shotcrete
with swellex bolts for ground support
. Open stopes will be backfilled with waste rock from the open pit hauled down the decline by empty ore trucks return from surface and mixed with cement
underground. Barrick's Goldstrike Mine utilizes paste backfill, which is an alternative for Cortez in the future which may simplify the backfill process. Once the mine is in full operation it is estimated to have up to twelve production faces in operation producing 1200 short tons (1,088.6 t) per day of ore in 2009.
heap leaching or milling at the Pipeline mill. Low grade open pit ore is heap leached without further crushing at one of the two leach pads currently in operation. The larger leach pad is 3.6 million ft2 (362,000m2) with a 20,000 US gal
/min (1,250 l/s) flow rate. The smaller pad is connected to the Pipeline mill and has a flow rate of 6,000 US gal/min (375 l/s). Higher grade ore is processed at the Pipeline mill utilizing CIC/CIL (carbon in column/carbon in leach).
in Nevada.
hillsides that were clearcut
in the 1800s and remove an obsolete roaster that has not been utilized since the 1980s. Working with the United States Bureau of Land Management and the Nevada Department of Wildlife
Cortez has already revegetated
some of their old waste dumps by placing alluvium over the waste rock and planting local vegetation in the area
s where it is pumped to ranch land to be reintroduced into the groundwater supply. The mine keeps two streams of water, a contact water stream in which the water has come into contact with the mining operation, and a non-contact water stream where the water has not come into contact with the mining operation. The 'contact water stream is recycled and reused in the mining operation where the noncontact water is pumped off site.
The Timbisha Shoshone Tribe
are calling for a stop to the Cortez Hills expansion, saying it the damage that will be done to the land is irreversible and prevent the use of the lands for religious purposes. Barrick had taken part in a collaborative agreement with leaders of the four remaining Shoshone Tribes.
A preliminary injunction
requested by Western Shoshone activists was placed on Barrick to prevent the company from developing the Cortez Hills Mine expansion. Although the request was denied at the district level, a preliminary injunction was issued by the 9th Circuit, which could stop the project completely if the judge determines the project would cause the environment irreversible damage and restrict the religious freedom
of the Western Shoshone. The focal point is Mount Tenabo
(of which Barrick would be mining the flank of, should the Cortez Hills Mine proceed as planned) and whether it is significant to the Western Shoshone culture as claimed.
Barrick lawyers maintain that Mount Tenabo has been mined since 1862.
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
mining
Mining
Mining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or seam. The term also includes the removal of soil. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock...
and processing
Mineral processing
In the field of extractive metallurgy, mineral processing, also known as mineral dressing or ore dressing, is the process of separating commercially valuable minerals from their ores.-History:...
facility in Lander
Lander County, Nevada
Lander County is a county located in the U.S. state of Nevada. As of the 2000 census, the population was 5,794. Its county seat is Battle Mountain.-History:...
and Eureka County
Eureka County, Nevada
Eureka County is a county located in the U.S. state of Nevada. As of the 2000 census, the population was 1,651. Its county seat is Eureka.Eureka County is part of the Elko Micropolitan Statistical Area.-History:...
, Nevada
Nevada
Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...
, United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, located approximately 75 miles (120.7 km) southwest of Elko
Elko, Nevada
Elko is a city in Elko County, Nevada, United States. The population was 18,297 at the 2010 census. It is the county seat of Elko County. The city straddles the Humboldt River....
. It is owned and operated by Barrick Gold
Barrick Gold
Barrick Gold Corporation is the largest pure gold mining company in the world, with its headquarters in Toronto, Ontario, Canada; and four regional business units located in Australia, Africa, North America and South America...
and is made up of the Pipeline and South Pipeline deposits and the Cortez Hills deposit. The Pipeline and South Pipeline are open pit
Open-pit mining
Open-pit mining or opencast mining refers to a method of extracting rock or minerals from the earth by their removal from an open pit or borrow....
mines, and the Cortez Hills deposit, currently under construction will utilize both underground and open pit mining techniques. Under continuous operation, Cortez has been open longer than any gold mine in the state of Nevada. It will become Barrick's largest gold producer in Nevada, in part because of the decline in production from their Goldstrike mine
Goldstrike mine
Barrick Goldstrike is a gold mine in North Eastern Nevada, Lynn District, Eureka County. It is located on the Carlin Trend where several other mines are found. Barrick Gold started mining Goldstrike in 1986. It is a part of the largest gold mining company in North America, Barrick...
and the development of the Cortez Hills deposit.
Region history
Cortez Mountains
The Cortez Mountains are located in central Nevada in the United States. The range lies in a southwest-northeasterly direction between Crescent Valley and Pine Valley. Mount Tenabo is the principal peak of the range, at 9,162 feet above sea level....
has been mined since 1862, with silver
Silver
Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
being the primary commodity the 1940s. The Gold Acres operation in the Cortez Mountains included open pit and underground mines in the 1930s and 1940s. Cortez Gold opened in 1968 and production ended in 1976. The United States Bureau of Mines
United States Bureau of Mines
For most of the 20th century, the U.S. Bureau of Mines was the primary United States Government agency conducting scientific research and disseminating information on the extraction, processing, use, and conservation of mineral resources.- Summary :...
built a pilot plant
Pilot plant
A pilot plant is a small chemical processing system which is operated to generate information about the behavior of the system for use in design of larger facilities....
in 1969 which would made heap leaching
Heap leaching
Heap leaching is an industrial mining process to extract precious metals, copper, uranium, and other compounds from ore.The process has ancient origins; one of the classical methods for the manufacture of copperas was to heap up iron pyrite and collect the leachate from the heap, which was then...
for gold in commercially viable by 1971. The low grade ore
Ore
An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....
and dump material from the Gold Acres operation was then heap leached. The Cortez mill
Gold extraction
Gold extraction or recovery from its ores may require a combination of comminution, mineral processing, hydrometallurgical, and pyrometallurgical processes to be performed on the ore....
was reopened as the price of gold increased in the early 1980s, feed for the mill was provided by the nearby Horse Canyon deposit between 1983 and 1987. Further exploration of the region was carried out by Cortez Joint Venture which involved Placer Dome
Placer Dome
Placer Dome Inc. was a large mining company specializing in gold and other precious metals, with corporate headquarters in Vancouver, British Columbia, Canada....
and Kenecott
Kennecott Utah Copper
Kennecott Utah Copper Corporation , a division of Rio Tinto Group, is a mining, smelting, and refining company. Its corporate headquarters are located in South Jordan, Utah, USA. Kennecott operates one of the largest open-pit copper mines in the world in Bingham Canyon, Salt Lake County, Utah. ...
( at the time Kenecott was a BP Minerals
BP
BP p.l.c. is a global oil and gas company headquartered in London, United Kingdom. It is the third-largest energy company and fourth-largest company in the world measured by revenues and one of the six oil and gas "supermajors"...
subsidiary
Subsidiary
A subsidiary company, subsidiary, or daughter company is a company that is completely or partly owned and wholly controlled by another company that owns more than half of the subsidiary's stock. The subsidiary can be a company, corporation, or limited liability company. In some cases it is a...
). The result of the joint venture's exploration was the 1991 discovery of the Pipeline orebody. The Pipeline orebody was located near the Gold Acres operation, instead of being located in the foothills, it was entirely within the Crescent Valley. The Pipeline orebody was much larger than the original orebodies in the region. The entire Pipeline complex contained 23 million ounces of gold between the original orebodies, the Pipeline orebody and the later discoveries of South Pipeline, Crossroads and Gap. The Cortez Joint Venture built the Pipeline Mine and mill in early 1996 following a series of ownership disputes with junior mining companies. Commissioning of the Pipeline mine cost US$
United States dollar
The United States dollar , also referred to as the American dollar, is the official currency of the United States of America. It is divided into 100 smaller units called cents or pennies....
250 million, and resulted an annual output between 1998 and 2005 of over one million ounces of gold per year. The Cortez Hills deposit was discovered in 2002, underground development to define the resource limits began in 2006. Barrick Gold acquired 60% in Cortez in 2006 when it purchased Placer Dome for US$10.4 billion, and acquired the remaining 40% from Rio Tinto
Rio Tinto Group
The Rio Tinto Group is a diversified, British-Australian, multinational mining and resources group with headquarters in London and Melbourne. The company was founded in 1873, when a multinational consortium of investors purchased a mine complex on the Rio Tinto river, in Huelva, Spain from the...
in March 2008 for US$1.7 billion.
Geology
The Cortez Mine is located in the Crescent Valley which is between the ShoshoneShoshone Mountains
also located in Nye County.The Shoshone Mountains, in central Nevada, make up one of the longest mountain ranges in the state. The range runs in a north-south direction, mostly in Nye County, but also occupies part of Lander County...
and Cortez Mountains
Cortez Mountains
The Cortez Mountains are located in central Nevada in the United States. The range lies in a southwest-northeasterly direction between Crescent Valley and Pine Valley. Mount Tenabo is the principal peak of the range, at 9,162 feet above sea level....
, a basin in the traditional Basin and Range
Basin and Range
The Basin and Range Province is a vast physiographic region defined by a unique topographic expression. Basin and Range topography is characterized by abrupt changes in elevation, alternating between narrow faulted mountain chains and flat arid valleys or basins...
setting of Nevada
Nevada
Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...
. Precious metal
Precious metal
A precious metal is a rare, naturally occurring metallic chemical element of high economic value.Chemically, the precious metals are less reactive than most elements, have high lustre, are softer or more ductile, and have higher melting points than other metals...
mineralization
Mineralization
Mineralization may refer to:* Mineralization , the process through which an organic substance becomes impregnated by inorganic substances...
came during Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
-Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
periods. The Pipeline complex lies within 600 feet (183 m) of silt
Silt
Silt is granular material of a size somewhere between sand and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil or as suspended sediment in a surface water body...
y limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
in what is called the Silurian
Silurian
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...
Roberts Mountain Formation. Above this is Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
Wenban Limestone, which acts as the host rock of the Cortez Hills deposit. Above the Devonian Limestone is Quaternary
Quaternary
The Quaternary Period is the most recent of the three periods of the Cenozoic Era in the geologic time scale of the ICS. It follows the Neogene Period, spanning 2.588 ± 0.005 million years ago to the present...
alluvium
Alluvium
Alluvium is loose, unconsolidated soil or sediments, eroded, deposited, and reshaped by water in some form in a non-marine setting. Alluvium is typically made up of a variety of materials, including fine particles of silt and clay and larger particles of sand and gravel...
.
Mining operations
Surface
Current haulage rates at Cortez are 350000–400000 ST (317,514.7–362,873.9 t) per day of combined ore and waste, and will increase with the commissioning of the Cortez Hills open pit. Cortez currently has an average stripping ratioStripping ratio
In mining, stripping ratio or strip ratio refers to the ratio of the volume of overburden required to be removed to the volume of ore recovered...
of 3:1. Ore in the open pit mines is hauled on surface using 400 short tons (362.9 t) Liebherr
Liebherr
* The Liebherr Group, a German manufacturing complex established in 1949 by Hans Liebherr* Liebherr Grazer AK* Liebherr T 282B, an off- highway, ultra class, rigid frame, two- axle, diesel/electricappointed...
T282B
Liebherr T 282B
The Liebherr T 282B is an off-highway, ultra class, rigid frame, two-axle, diesel/electric, AC powertrain haul truck designed and manufactured by the Liebherr Mining Equipment Co. in Newport News, Virginia, USA...
trucks
Dump truck
A dump truck is a truck used for transporting loose material for construction. A typical dump truck is equipped with a hydraulically operated open-box bed hinged at the rear, the front of which can be lifted up to allow the contents to be deposited on the ground behind the truck at the site of...
. Cortez currently owns 24 T282Bs, which accounts for 10% of the total sales of T282 & T282B trucks worldwide.
Underground
The underground operation at Cortez Hills utilizes parallel 16 feet (4.9 m) wide by 18 feet (5.5 m) high, 10000 feet (3,048 m) declines. Crosscuts connect the declines every 500 feet (152.4 m), the ramps are driven at a grade of 6% for their entirety. The declines are used to haul ore from the stopesStoping (mining method)
Stoping is the removal of the wanted ore from an underground mine leaving behind an open space known as a stope. Stoping is used when the country rock is sufficiently strong not to cave into the stope, although in most cases artificial support is also provided...
to surface and to provide ventilation
Underground mine ventilation
Underground mine ventilation provides a flow of air to the underground workings of a mine of sufficient volume to dilute and remove noxious gases . The source of these gases are equipment that runs on diesel engines, blasting with explosives, and the orebody itself...
for the mining operation. The declines are accessed via portals
Adit
An adit is an entrance to an underground mine which is horizontal or nearly horizontal, by which the mine can be entered, drained of water, and ventilated.-Construction:...
on the wall of an old open pit, the haulage (west) decline brings fresh air into the mine and the east decline exhausts air to surface.
The declines and lateral development utilize welded wire mesh and shotcrete
Shotcrete
Shotcrete is concrete conveyed through a hose and pneumatically projected at high velocity onto a surface, as a construction technique....
with swellex bolts for ground support
Rock mechanics
Rock mechanics is the theoretical and applied science of the mechanical behaviour of rock and rock masses;also compared to the geology, it is that branch of mechanics concerned with the response of rock and rock masses to the force fields of their physical environment.Rock mechanics itself forms...
. Open stopes will be backfilled with waste rock from the open pit hauled down the decline by empty ore trucks return from surface and mixed with cement
Cement
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...
underground. Barrick's Goldstrike Mine utilizes paste backfill, which is an alternative for Cortez in the future which may simplify the backfill process. Once the mine is in full operation it is estimated to have up to twelve production faces in operation producing 1200 short tons (1,088.6 t) per day of ore in 2009.
Pipeline deposits
Processing of ore from the Pipeline deposits is done by either cyanideCyanide
A cyanide is a chemical compound that contains the cyano group, -C≡N, which consists of a carbon atom triple-bonded to a nitrogen atom. Cyanides most commonly refer to salts of the anion CN−. Most cyanides are highly toxic....
heap leaching or milling at the Pipeline mill. Low grade open pit ore is heap leached without further crushing at one of the two leach pads currently in operation. The larger leach pad is 3.6 million ft2 (362,000m2) with a 20,000 US gal
Gallon
The gallon is a measure of volume. Historically it has had many different definitions, but there are three definitions in current use: the imperial gallon which is used in the United Kingdom and semi-officially within Canada, the United States liquid gallon and the lesser used United States dry...
/min (1,250 l/s) flow rate. The smaller pad is connected to the Pipeline mill and has a flow rate of 6,000 US gal/min (375 l/s). Higher grade ore is processed at the Pipeline mill utilizing CIC/CIL (carbon in column/carbon in leach).
Cortez Hills deposit
Low grade ore from open pit at the Cortez Hills deposit will be heap leached at dedicated heap leach pads at Cortez Hills site, while ore from the underground mine will be mixed with higher grade open pit and will be sent 10 miles (16 km) to the Pipeline mill via the largest overland conveyorConveyor system
A conveyor system is a common piece of mechanical handling equipment that moves materials from one location to another. Conveyors are especially useful in applications involving the transportation of heavy or bulky materials...
in Nevada.
Environment
In order to bring the Cortez Hills Mine into operation, Barrick will have to move a road that runs through the Cortez Canyon which will cost US$15 million. Barrick will reforestReforestation
Reforestation is the natural or intentional restocking of existing forests and woodlands that have been depleted, usually through deforestation....
hillsides that were clearcut
Clearcutting
Clearcutting, or clearfelling, is a controversial forestry/logging practice in which most or all trees in an area are uniformly cut down. Clearcutting, along with shelterwood and seed tree harvests, is used by foresters to create certain types of forest ecosystems and to promote select species that...
in the 1800s and remove an obsolete roaster that has not been utilized since the 1980s. Working with the United States Bureau of Land Management and the Nevada Department of Wildlife
Nevada Department of Wildlife
The Nevada Department of Wildlife is the state agency responsible for the restoration and management of fish and wildlife resources, and the promotion of boating safety on Nevada’s waters. NDOW has responsibility for the wildlife resources and enforcement of the wildlife and boating safety laws on...
Cortez has already revegetated
Revegetation
Revegetation is the process of replanting and rebuilding the soil of disturbed land. This may be a natural process produced by plant colonization and succession, or an artificial , accelerated process designed to repair damage to a landscape due to wildfire, mining, flood, or other cause...
some of their old waste dumps by placing alluvium over the waste rock and planting local vegetation in the area
Water
Northern Nevada has a limited supply of surface water which is considered a precious commodity, however large amounts of water can be found underground. At the Pipeline pit water is pumped from aquiferAquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...
s where it is pumped to ranch land to be reintroduced into the groundwater supply. The mine keeps two streams of water, a contact water stream in which the water has come into contact with the mining operation, and a non-contact water stream where the water has not come into contact with the mining operation. The 'contact water stream is recycled and reused in the mining operation where the noncontact water is pumped off site.
Native Americans
Shoshone
The Shoshone or Shoshoni are a Native American tribe in the United States with three large divisions: the Northern, the Western and the Eastern....
are calling for a stop to the Cortez Hills expansion, saying it the damage that will be done to the land is irreversible and prevent the use of the lands for religious purposes. Barrick had taken part in a collaborative agreement with leaders of the four remaining Shoshone Tribes.
A preliminary injunction
Preliminary injunction
A preliminary injunction, in equity, is an injunction entered by a court prior to a final determination of the merits of a legal case, in order to restrain a party from going forward with a course of conduct or compelling a party to continue with a course of conduct until the case has been decided...
requested by Western Shoshone activists was placed on Barrick to prevent the company from developing the Cortez Hills Mine expansion. Although the request was denied at the district level, a preliminary injunction was issued by the 9th Circuit, which could stop the project completely if the judge determines the project would cause the environment irreversible damage and restrict the religious freedom
Freedom of religion in the United States
In the United States, freedom of religion is a constitutionally guaranteed right provided in the religion clauses of the First Amendment. Freedom of religion is also closely associated with separation of church and state, a concept advocated by Thomas Jefferson....
of the Western Shoshone. The focal point is Mount Tenabo
Mount Tenabo
Mount Tenabo is the principal peak in the Cortez Mountains. The Western Shoshone people assert that the mountain is of cultural and religious significance....
(of which Barrick would be mining the flank of, should the Cortez Hills Mine proceed as planned) and whether it is significant to the Western Shoshone culture as claimed.
Barrick lawyers maintain that Mount Tenabo has been mined since 1862.