Just after that, the mining of copper ore took over. Chalcopyrite at Dyråsen mines and in Atramadalen was taken out at the same time as copper was being mined at Røros. The mining operations on the Ølve peninsula continued all the way until 1911.
The basis for the mining was the rock type greenschist. Many of the mines from the over 300 year-old pyrite industry in Norway are associated with greenschist occurrences. The greenschist belt from Ølve to Varaldsøy Island is comprised of remnants of the old sea that existed between Greenland and Norway about 500 million years ago. The basis for the greenschists arose when lava and ash spewed out of the volcanic islands in this prehistoric "Atlantic Ocean" - an ocean that has since closed. During its closure, as Greenland and Norway got nearer to each other, the lava was pressed down to great depths together with layers of mud and clay. When the land areas collided afterward, the Caledonian Mountain chain was formed. The lava was heated and transformed into greenschist, and the mud and clay into mica schist, simultaneously as they were transported in over the bedrock of Hordaland. The layers were folded both under this transport and during later movements along Hardanger Fjord. The pyrite ore is mostly copper-rich sulphur ore with a little iron ore (magnetite and hematite), and is believed to have been formed on the sea floor of the prehistoric ocean. The ore was formed from hot gasses and liquid that was rich in iron and sulphur that flowed up through cracks and volcanic feeder pipes.
