The Kylylahti project is located approximately 22 km northeast of the historic mining town of Outokumpu in the Karelia district of Finland. The Keretti coppercobalt-zinc-gold deposit, which underlies the modern town of Outokumpu, was discovered in 1910 following the location of the source of a massive sulphide glacial boulder found some 50 km to the southeast.

The Kylylahti deposit lies within a region and in a geological environment which has a long history of mining. As such the nature of the mineralisation and the metallogeny are well known, although the local controls on ore localisation are becoming apparent through deposit-scale drilling. The mineralisation can be identified visually, leading to low risks associated with the identification and delineation of the orebodies. In Snowden’s opinion there is considerable upside in the quantity of ore to be discovered, particularly in the down-dip area of the Wombat zone and in the somewhat complex area of overlap of the Wallaby and Wombat zones.

The mining method used is longitudinal openstoping with cemented rock fill(CRF) and/or waste rock fill. Parts of the orebody, however, will be mined using upward stoping without backfill. The stopes vary in dimension as follows: Heights between 8 metres and 30 metres, lengths between 20 metres and 50 metres and width in average between 4 metres and 12 metres.

A 5.5 x 5.5 metre decline is used for ore transportation and access to development drives. Level spacing is 25-30 metres vertical, and development drives are connected to the decline by access drives. In the upper parts of the mine (levels 50 to 150) access drives are located at the southern end of the orebody, in the middle parts (levels 180 to 300) access drives enter the orebody in the middle, and development drives extend to the north and south. In the lower parts (levels 325 and 350) the decline moves around the orebody from the footwall to hangingwall side, and accesses the orebody from the northern end. On level 380 the access is again at the southern end of the orebody.

Stoping generally proceeds from the northern and southern ends of the orebody, with mining upwards from the bottom. Due to the orebody plunging approximately ~25° to the south-west, the northernmost stopes on each level can be mined as a bottom level stope.

In areas where stopes can be accessed from above, the front end of the stopes will be filled with CRF. The next stope opening will then be blasted so that no pillar will be left against the CRF wall, thus maximising ore recovery.

Stope designs generally include dilution to ensure that the shapes are practical and can be mined and extracted. This dilution is included in the stope tonnes and grades as planned dilution. In addition, overbreak is assumed as unplanned dilution. The unplanned dilution factor applied is dependent upon the stope width and shape. It is assumed that approximately 0.5 metres of overbreak will occur on both sidewalls of the stope. Therefore dilution varies between 5% in wide stopes (>20 metres) and 25% in narrow stopes (4 metres). When stope shape and stope location is seen as being exceptionally difficult an additional dilution factor of 2 to 10% is used.

Unplanned dilution is anticipated to come from footwall and hangingwall in a 50/50 ratio. The diluting material carries metal grades. The dilution grades that are used are calculated average resource model values for both Wallaby and Wombat orebodies assuming a 0.5 m thick layer on both sides of the stope.

The recovery from planned stopes is assumed to be 90% for open stoping and 85% for upward stoping.

The metallurgical process is well established; 3 stage crushing, rod mill and pebble mill followed by flotation to produce copper-gold concentrate and a zinc concentrate for sale, together with a low-grade cobalt-nickel concentrate for storage end a sulphur concentrate for disposal. The flowsheet is virtually identical to that employed at the plant in the past for 15 years of treating similar ore.

Metallurgical recoveries are well established and vary slightly with head grade on average the recoveries are:
- Copper 92.1%
- Gold 74.9%
- Zinc 49.0%.