Grimsdalen & Nygruva
The Grimsdalen deposit is by far the largest in the Folldal district, measuring approximately 9 km, with a maximum width of 1,000 m and an average thickness of 3 m. The deposit is hosted by banded tuffaceous schists with intercalations of graphitic schist and mineralisation dominated by pyrite, with pyrrhotite, chalcopyrite and sphalerite occurring in varying but generally subordinate amounts.
The Nygruva mine was in production over three periods from 1783 to 1952. In total 300,000t is recorded to have been produced at 0.85 % Cu and 3.5 % Zn (NGU Ore Database). The mineralised zone mined at Nygruva is ruler-shaped and has a length of 680 m, width of 60-70 m and an average thickness of 3 m. The massive part of the mineralisation comprises banded pyrite-sphalerite with lesser chalcopyrite and pyrrhotite in a quartz-calcite matrix. The stratigraphic footwall of the massive mineralisation contains irregular lenses of zinc- or copper-mineralisation. Two normal-faults cut across the deposit of which the westernmost one marks the end of the known deposit. Investigations to find the continuation have not been successful to date.