A number of metals are produced from oxide minerals. Iron, manganese, chromium, and tin are exclusively obtained from oxide ores. Rich ores, for example, hematite, pyrolusite, chromite, and so on can be directly reduced whereas lean ores are first concentrated by communication, classification, jigging, and tabling. Sulfide ores, such as galena and sphalerite concentrates, are first roasted to oxides for subsequent reduction to metals. Carbonate minerals, such as dolomite, are calcined prior to reduction into magnesium. However, oxides of noble metals like Ag2O, PtO, and PdO are decomposed to Ag, Pt, and Pd at temperatures of 200 °C, 500 °C, and 900 °C, respectively.