The previously mined Ryllshyttan Zn-Pb-Ag-(Cu) + magnetite deposit comprised approximately 1 Mt sphalerite-dominated massive sulphide ore and about 200 000 tons of massive to semi-massive skarn-limestone hosted magnetite ore. Ryllshyttan belongs to the Bergslagen ore district of south central Sweden, a Palaeoproterozoic igneous province renowned for its abundance and diversity of Fe-oxide and sulphide mineralisations. Ryllshyttan's ore-bodies are hosted by a carbonate horizon partially altered to skarns of tremolite, diopside-salite and andradite. The ore horizon itself is enclosed by volcanics and intrusions belonging to the earliest Svecokarelian igneous rocks (~ 1.9 Ga BP). The stratigraphy follows a first order volcanic cycle with an evolution from juvenile rhyolitic mass flow deposition to deposition of rhyolitic ash-siltstones intercalated with ferruginous-calcareous chemical and/or hydrothermal sediments. Observations suggest that iron oxides started to accumulate syngenetically at the time of host-rock formation. In contrast, sulphides are associated with discordant Mg +/- K +/- Si alteration that also overprints some intrusions. Consequently, sulphide mineralization and the earliest iron oxide mineralization are attributed to separate events.