Kylylahti - Processing

A metallurgical and mineralogical classification of the deposit was undertaken to ensure the representativeness of samples used in testwork. Extensive prior mineralogical and metallurgical testwork by Outokumpu Oy also informed the testwork programme. Flotation testwork was undertaken at Ammtec in Perth and Outotec completed roasting and leaching testwork on bulk concentrates as part of the Definitive Feasibility Study ("DFS").

Physical testwork was undertaken at Ammtec and a milling circuit comprising a single stage fully autogenous grinding mill with a pebble crusher was recommended by Orway Mineral Consultants which is consistent with past practice at Outokumpu.

A standard flotation circuit is proposed with a copper removal stage followed by cleaning of the tail to generate a bulk concentrate. The copper-gold concentrate is optimised for grade and recovery to maximise payments from smelters and the bulk cobalt-nickel-zinc-copper concentrate is optimised to maximise both sulphur and metal recovery rather than payable metal grades. Sulphur is a key driver for bulk concentrate processors.

Flotation recoveries vary through the mine life dependant on the relative proportions of pyrite rich semi-massive sulphides and of pyrrhotite rich disseminated sulphides. Mine production has been classified in this way and the metallurgical performance modelled over the entire mine life.

Recoveries to the bulk concentrate are:

    Cobalt: 95-96%
    Nickel: 84-86%
    Zinc: 86-92%
    Copper: 14-23%

Recoveries to copper-gold concentrate are:

    Copper: 75-86%
    Gold: 62-64%

Copper-gold concentrate grades are:

    Copper: 27-28%
    Gold: 10-14 g/t

The concentrate is filtered, dried to 8% moisture and stored in a concentrate shed prior to transport to market.

Concentrator, Infrastructure and Paste Plant

SNC completed the design and costing of the concentrator and its associated infrastructure including power reticulation, mine air heating facility, access roads, ROM pads, waste dumps, water management, administration buildings, etc. The value engineering and review validated the flowsheet, adjusted for higher throughputs and improved confidence in capital cost estimates. Golder Associates and Pastec designed and costed the tailings storage facility and the paste plant and Turnbery Pty Ltd reviewed and optimised the paste plant.

A geotechnical and hydrological investigation of ground characteristics was conducted for buildings and tailings foundations.

The concentrator is 400 metres from a tarmac highway and is located 2 kilometres from the town of Polvijärvi. The mine site is adjacent to a regional electrical transmission line and power will be delivered via a 110kV/20kV substation.