This year will represent a significant milestone for Michigan’s Upper Peninsula with the commissioning of Lundin Mining’s Eagle mine. It will be Michigan’s first nickel mine, and the first mine in the USA in which nickel is the primary metal rather than a byproduct. Average production is expected to be 23,000 t/y of nickel, 20,000 t/y of copper, plus PGM and cobalt credits over the mine’s first three years of full production.
XPS has been working on the project for some years. Its history with the Eagle mine dates back to when a former owner contracted XPS to develop toll milling options for the ore. Lundin’s decision to refurbish the nearby Humboldt mill in Marquette County resulted in a new round of flowsheet confirmation and piloting, in which XPS was happy to participate. Development work at XPS included both batch testing and continuous piloting in the XPS Flotation Mini Pilot Plant.
The pilot plant, which was operated at approximately 12kg/hr, produced a bulk Cu-Ni concentrate at grades over 22% Cu+Ni in concentrate. The pilot plant produced scaleable operating results requiring only about 300 kg/d of ore. This low quantity of sample is a big advantage as the cost of acquiring ore sample is significantly lower with the XPS Mini Pilot Plant versus conventional pilot plants.
The pilot operation employed the new XPS Laboratory Information Management (LIMS) system which in combination with rapid laboratory XRF assays allowed the construction of materials balances one hour after sample collection, at a frequency of one sample set per three hours. With this level of information feedback the stabilisation of the pilot operation was so rapid that XPS succeeded in fully meeting the project objectives within a day and a half from startup, and was able over the four day pilot campaign to test and stabilise two flowsheet alternatives above and beyond client expectations.
The bulk piloting campaign was followed by a Cu-Ni separation campaign using accumulated concentrate, in which samples of final Ni and Cu concentrates were produced for testing and marketing evaluation.
XPS is continuing to work with Lundin Mining on pre-startup refinement of the metallurgical recovery model and is looking forward to providing on-site plant support as this landmark nickel project proceeds toward successful start-up and commissioning. XPS will be offering multidisciplinary on-site support in the areas of metallurgical diagnostics, determination of optimum operating conditions, process control and loop tuning, and materials technology.
The property is on the watershed divide of the Yellow Dog River and Salmon Trout Rivers, with the closest community to the mine site being Big Bay, 24 km from the property by road. Big Bay is an unincorporated community within Powell Township and has limited services. The closest full service community is Marquette, 53 km by road from the property. Marquette provides a regional airport, rail and shipping facilities, and a full range of commercial services.
The Humboldt mill property, a former iron ore processing facility, occupying approximately 142 ha, is located 61 km west of Marquette, Michigan. The facility is located in the township of Humboldt, Marquette County, Michigan. Ore from the Eagle mine will be trucked 105 km to the Humboldt mill for processing.
Road access to the mine property is by means of maintained loose surface and paved roads from the communities of Big Bay to the east, L’Anse to the west, and Marquette to the south. The Humbolt mill is located close to the main US Route 41.
The Eagle deposit is a high-grade magmatic sulphide deposit containing nickel and copper mineralisation and minor amounts of cobalt, precious and PGMs. The economic minerals associated with this deposit are predominately pentlandite and chalcopyrite.
Three distinct types of sulphide mineralisation occur in the deposit. They are described as disseminated, semi-massive and massive sulphide. Massive sulphide is generally over 90% pyrrhotite-pentlandite-chalcopyrite. Semi-massive, or matrix ore, is 30% or greater net textured sulphide. Disseminated mineralization is generally uneconomic. The semi-massive and massive sulphides occur in separate zones called the Massive Sulphide, Semi-massive East, and Semi-massive West zones.
Eagle is a relatively shallow underground mine with access gained via a surface ramp that will serve as the route for waste, ore and backfill haulage. The mine will employ transverse bench-and-fill stoping with mining in an up-dip primary secondary sequence. Backfilling will be undertaken using cemented and uncemented rockfill. Two ventilation shafts are in place, with the downcast shaft also equipped for emergency egress. Ore from the mine will be stored in a covered coarse ore stockpile facility prior to transport to the Humbolt mill site.
From a further covered coarse ore storage facility at Humbolt, the ore will be processed using a conventional crush, grind and differential flotation process to produce separate nickel and copper concentrates. Tailings from the plant will be deposited sub-aqueously in the adjacent former Humbolt iron ore open pit.
Nickel and copper concentrates will be stored in a covered concentrate building on site. A rail spur in to the site will be used to transport the concentrate direct to smelter facilities within North America or to the ports of Quebec, Montreal or Vancouver for shipment to overseas smelters.