The Pyhäsalmi deposit is a copper-zinc volcanogenic massive sulphide deposit of Proterozoic age. The mineralization is hosted by altered felsic and mafic volcanic rocks. The enveloping alteration zone is at least four kilometres long and one kilometer wide at its widest point. Alteration of the felsic volcanic rocks includes sericite and cordierite dominated mineralogy. Cordierite, anthophyllite and garnet dominate in the altered mafic volcanic rocks. The metamorphic grade is upper amphibolite facies.

The upper part of the Pyhäsalmi deposit was mined between 1962 and 2001 and is now depleted. Deep drilling in 1996 led to the discovery of an extension to the deposit below the +1050 meter level. The newer deep deposit is located between the +1050 meter level (from surface) and the +1416 meter level. The inner part of the lens consists of massive pyrite with low copper and zinc values. This core is surrounded by massive chalcopyrite-pyrite and the outer rim consists of massive sphalerite pyrite. The main sulphide minerals are pyrite (65%), chalcopyrite (3%), sphalerite (4%) and pyrrhotite (3%).

Underground mining of copper and zinc at Phyasalmi ended in August 2022.

Starting in 2023, pyrite-rich material will be excavated and transported from a storage pond located about a kilometer away to the concentrator for enrichment. It is estimated that the operation will continue for about four years.

Approximately 2 million tonnes of pyrite rich material is estimated to be reclaimed from B pond in the coming years for third party sales. The pond is drained and the material is piled up to dry with an excavator. The material is transported by trucks to the concentrator for enrichment.

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