Dunderland valley

    The Dunderland valley is known for its many iron oxide deposits. The horizons belong to a super group deposited in a submarine basin probably 1000 million years ago. The dominating rocks of the super group are various types of mica shists, dolomitic marbles, limestones, amphibolites and quartzites. The iron ore contains an average of 33% iron in the forms of the oxide minerals hematite (Fe2O3) and magnetite (Fe3O4). Hematite makes up 97.5% to 98% of the iron oxides. Magnetite corresponds to 2.5% to 2.0% in the Kvannevann mine. Other ore bodies may contain up to 15% Magnetite.

    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 occurrence 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.
    Polish section Ørtfjell.

    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.

    The host rock for the iron oxide minerals is made up by quartz, feldspar, Fe-Al-silicates and carbonates. 
    Rockforming minerals Ørtfjell.

    The ore concentrations are spread over an area of approximately 45 km2. The current mining is concentrated around Ørtfjell with three major deposits. The iron ore resources have been estimated to approximately 500 mill tons until 100 m above sea-level The ore seams are from a few meters to hundred meters thick and strongly folded. In the Ørtfjell area they almost are vertical with unknown extension to depth.