Mt Hope open-pit molybdenum mine is located to the north-west of Eureka, Nevada, Canada. It is considered to be one of the world’s biggest and highest-grade molybdenum deposits. The project includes the development of an open pit mining operation and associated infrastructure to process molybdenite sulphide (MoS2) ore.
Eureka Moly (EMLLC), a joint venture between General Moly and POS-Minerals, owns the project. General Moly holds an 80% stake in the project, while the remaining 20% is owned by POS-Minerals, a subsidiary of POSCO.
EMLLC received Record of Decision and environmental permits to construct and operate the mine in 2012. First milling of ore is expected in the third quarter of 2016.
The molybdenum mine is estimated to have a mine life of 34 years, whereas the processing plant will operate for an additional seven years to mill the low-grade stockpile. During its lifetime the mine is expected to produce 1.2 billion pounds of saleable molybdenum in the form of technical grade molybdenum oxide (TMO). It is anticipated to produce 24Mt a year of high-grade ore, and to have a mill throughput of 66,688t a day.
The Gibraltar copper-molybdenum open pit mine located in British Colombia
Mt Hope project history, details, geology and mineralisation
Exploration and mining of molybdenum at the Mt Hope mine began in 1870s. Idaho General Mines, now known as General Moly, optioned the mine in 2004 and conducted a feasibility study.
The mine is located partly on federal lands managed by the Bureau of Land Management (BLM) land, and partly on private land held by Mt Hope Mines (MHMI). EMLLC obtained the land on lease from MHMI for 30 years.
The deposit lies in a topographically elevated area including a high level of igneous rock exposure. It hosts extrusive and intrusive rocks composed of rhyolite. The rocks demonstrate textual similarities, as they were derived from a common magmatic source.
The deposit is classic molybdenum porphyry, much the same as the Climax deposit in Colorado. It is categorised into mineral zones, or shells, comprising quartz porphyry rocks veined by quartz stockwork containing molybdenite.
Molybdenum mineralisation at Mt Hope is primarily in the form of molybdenite (MoS2), organised within porphyritic igneous rocks and in Vinini hornfels. Most of the mineral is disseminated around two inverted dome shaped zones of mineralised stockworks.
Reserves at the Mt Hope molybdenum mine
The mine is estimated to hold proven and probable ore reserves of 984.6Mt grading 0.034% of sulfide molybdenum.
As of 31 December 2013, the mine is estimated to contain proven and probable reserves of 1.4 billion pounds of molybdenum.
Mining and processing of ore at Mt Hope
Mt Hope will use a conventional open pit method of mining, involving drilling, blasting, and loading. The ore and wastes will be delivered to the crusher and waste storage facilities respectively. The mine plan includes the delivery of 66,688tpd of flotation ore to the crusher, while the low-grade material will be stockpiled for processing after the end of mine life.
The mining fleet during the initial stages will include two P&H 2800 class electric shovels, a CAT 6060 hydraulic shovel, two front-end loaders, and CAT 793 haul trucks.
The run-of-mine (ROM) ore will be trucked from the mine to the primary crusher, where it will be stockpiled to be later ground to rougher flotation feed size in the primary grinding circuit of a SAG mill-ball mill (SAB). The SAG mill will operate in closed circuit with a trommel screen and a vibrating screen, while the ball mills will operate in closed circuit with hydrocyclones.
The ore will then pass through a rougher flotation circuit and six stages of cleaning in mechanical flotation cells, resulting in the production of molybdenite concentrate, which will be dewatered and dried before transportation to either packaging or roaster circuit.
Alternatively, the final cleaner flotation concentrate may be leached in a ferric chloride leach circuit to reduce any copper, lead and zinc impurities. The leached concentrate will be dewatered, dried and roasted in multiple-hearth roasters to produce technical grade molybdenum oxide (TMO). The molybdenum oxide product is packaged either as powder in drums or in super sacks.
Infrastructure facilities at the Mt Hope project
Power for the molybdenum project is proposed to be supplied via a new 40km-long, 230kV high-voltage power line originating at Nevada Energy’s transmission system at the Machacek Substation.
Key players involved with the Mt Hope molybdenum project development
M3 Engineering & Technology was engaged to conduct the feasibility study and prepare the technical report for the Mt Hope project.