Northmet

The property is composed of 7,500 acres acres located about 75 km north-east of Hibbing and near the town of Babbit in St Louis County in northern Minnesota, U.S.A.

The Northmet deposit hosts a proven and probable reserve of 249.2 Mt grading 0.28% copper, 0.08% nickel, 0.008% cobalt and 0.337 g/t precious metals.

The deposit lies adjacent to and immediately south of the Mesabi Iron Range, a 100 mile long geological feature in northern Minnesota that has been a historically important centre of iron ore production since the 1880s. It is a large-tonnage, disseminated accumulation of sulphide in mafic rocks with rare massive sulphides. Copper to nickel ratios generally range from 3:1 to 4:1.

PolyMet plans to mine the mineral deposit known as NorthMet by conventional open pit methods at a rate of 32,000 short tons per day of ore, and to extract base and precious metals.

The mining contractor will be responsible for equipment fleet maintenance and all associated costs are included in the contract rates used to develop mine operating costs.

Ore will be transported by mine haul trucks to a 3,600 tons rail transfer hopper located near the pit rim. The selected ore processing route involves four stages of crushing followed by rod and ball milling with conventional 3-stage flotation to produce a bulk sulphide flotation concentrate. Crushing, milling and flotation will occur in a reactivated former taconite iron ore processing plant, known as the Erie Plant and now owned by PolyMet.

The Erie Plant is 10 kilometers away from the NorthMet deposit and include crushing, milling, flotation capacity, comprehensive spare parts, plant site buildings, real estate, tailings impoundments and mine work shops, as well as access to extensive mining infrastructure including roads, rail, water and power. The new hydrometallurgical plant is planned to be installed adjacent to the existing mill on surplus land. There is an existing rail line between the NorthMet Deposit and the processing plant.

The existing plant includes two parallel coarse crushing trains, each consisting of one 60 inch primary gyratory crusher and four 36 inch secondary crushers. A 2,000 hp/ 1,500 kW IsaMill will be installed in the Concentrator building on Ball Mill 1S foundations to grind final flotation concentrate to P80 of 15 micrometer prior to pumping to the hydrometallurgical plant.

A new sulphide flotation circuit will be installed comprising two 250 m3 rougher flotation cells, ten 250 m3 scavenger flotation cells and ten 17 m3 cleaner flotation cells.

The bulk sulphide flotation concentrate will be subjected to autoclave pressure oxidation leaching followed by hydrometallurgical extractive processes to produce high purity copper cathode, mixed nickel and cobalt hydroxides and a mixed platinum group metals and gold precipitate (AuPGM). An existing tailings basin will be reactivated for flotation tailings and hydrometallurgical residue disposal.

An existing tailings basin will be reactivated for flotation tailings and hydrometallurgical residue disposal. Waste stockpile design will utilize a base or foundation liner and a cover system to encapsulate the contained waste rock and restrict entry of precipitation and snow melt.