The Kylylahti deposit is an elongate sulphide accumulation containing economic grades of copper, cobalt, nickel, gold and zinc. It is some 1.2 kilometres long and plunges at 30 degrees from surface where it is 5-10 metres thick to 650-700 metres deep where it is up to 60 metres thick and is not closed off by drilling. It is one of the deposits of the Outokumpu copper camp which founded the company of the same name and mining in the area commenced in 1914 until 1989.
Mineralisation generally comprises a footwall (east) layer of semi-massive sulphides comprising 40-80% sulphide (pyrite-pyrrhotite-chalcopyrite-sphalerite-quartz) enveloped by a thicker layer of disseminated sulphide of 5-40% sulphide, with lesser pyrite.