The Dunderland valley is known for its many iron oxide deposits. The horizons belong to a supergroup deposited in a submarine basin probably 1000 million years ago. The iron ore contains an average of 35% iron in the forms of the oxide minerals hematite (Fe2O3) and magnetite (Fe3O4).
Due to tectonic overprint of the host rock and the ore, the rock formation is grossly folded and shows a distinct cleavage underlined by the occurence of flaky hematite crystals (specularite). The magnetite crystals of the ore are on the contrary mainly isometric and partly show idiomorphic crystal faces. The main gangue minerals are: silicates, quartz and carbonates.
The hematite is proven to contain minor but detectable amounts of titanium (Ti) and very low contents of heavy metals. The magnetite is slightly enriched in manganese oxide (MnO) while the total amount of heavy metals does not exceed 360 ppm. The chemical and mineralogical properties of the ore minerals are proven to be stable throughout the mining areas.



Iron oxide mining started in the Dunderland valley more than 100 years ago. Until 1999 iron ore was only mined by open pit methods. Today Rana Gruber operates its Kvannevann mine situated in the Ørtfjell mining area some distance north of the village of Storforshei. A total of 1.6 million tonnes of ore is mined annually by underground open stope mining methods.
The board of directors has decided in June 2007 to open a new production level in the Kvannevann mine which will extend the lifetime of the mine. At this new production level operations will run until 2023 with a production cap of 2,1 million tonnes of run of mine.
New feasibility studies will be conducted well ahead of this time with respect to further extension of the mining operations.