Sedimentary host rocks - Concordant with bedding, extensive in two dimensions and restricted in the third. Example is the replacement of the Dolomite Breccias from the Silvermines Ireland. Examples are the Kupferschiefer of Central Europe and Sullivan, British Columbia. This group includes some of the true giants of ore deposits. Ores generally occur in sandstones with chalcopyrite, bornite and various uranium species the only ore minerals of consequence.
Ores appear to have been introduced after the sandstone was deposited, but prior to cementation.
Famous example is the Witwatersrand goldfield of South Africa. Rocks range in composition through the entire spectrum of compositions. Ore appear to occur as distinct horizons within the volcanic pile. Most studied example are the Kuroko deposits of Japan. Metamorphic host rocks - Only important as hosts of preexisting sedimentary or igneous deposits.