Eagle is located in the Upper Peninsula of Michigan, USA, in Michigamme Township of Marquette County. The closest community to the mine site is Big Bay, 24 km from the property by road and the closest full-service community is Marquette, approximately 53 km by road. Marquette provides a regional airport, rail and shipping facilities, and a full range of commercial services. Ore from the Eagle mine is trucked to the Humboldt mill, site of a former iron ore processing facility, for processing into concentrates. The Humboldt mill lies approximately 60 km west of Marquette.
Eagle mine is an approximately 2,000 tonnes per day (tpd) underground nickel-copper mine. The mine is relatively shallow with ramp access from surface. Ramp access to the Eagle East orebody is underway. The ramp is being developed with mine services and infrastructure being extend from the bottom of the Eagle mine. Eagle East will require no new surface infrastructure and is expected to utilize the same transverse bench-and-fill stoping mining method and basic stope dimensions as Eagle. Backfilling is undertaken using cemented and uncemented rockfill. Ore from the mine is stored in a covered coarse ore stockpile facility prior to transport by road approximately 105 km to the Humboldt mill.
The Humboldt mill is a former iron ore processing plant site that has been converted and refurbished to process Eagle ore. Ore is processed using a conventional three-stage crushing and single stage ball mill process flotation to produce separate nickel and copper concentrates. Tailings from the plant are deposited sub-aqueously in the adjacent former Humboldt iron ore pit that has been repurposed. No modifications to the process plant are necessary for the treatment of Eagle East ore which will be blended with Eagle ore.
Nickel and copper concentrates are stored in a covered concentrate building on site prior to being transport via rail car direct to smelter facilities within North America or ports for shipment overseas.
Geologic and Exploration Overview
Eagle and Eagle East are part of the same ultramafic intrusive system that hosts high grade primary magmatic nickel-copper sulphide mineralization. Mineralization styles are similar at Eagle and Eagle East, consisting of intrusions of mineralized peridotite with concentrations of sulphide mineralization mostly within the intrusion resulting in the accumulation of semi-massive and a central zone of massive sulphide.
Exploration activities at Eagle have included dyke lithogeochemistry, sulphur isotype studies, and geophysics (airborne, surface borehole resistivity and gravity, and 3D seismic survey). The main and most successful exploration tool has been diamond drilling in combination with a very robust and predictive deposit model.
Using the conduit model, the most direct and expedient exploration target was to follow the mineralized peridotite conduit at Eagle East to depth with direction drilling. With Eagle as a model, the Eagle East conduit was traced downward to a location where the conduit flattened to horizontal and high metal tenor sulphide droplets had settled to the base of the conduit. In 2018, exploration efforts continued to trace the extension of the Eagle East conduit system with four drill rigs.