Abstract: The invention relates to the production of tungsten having a low impurity content of molybdenum from impure minerals such as scheelite.An aqueous acidic feed solution containing both molybdenum and tungsten, and also containing enough hydrogen peroxide to depolymerize heteropolymers of tungsten and molybdenum and prevent precipitation in the extractant, is contacted with an extractant composition comprising an organic phosphoric acid, a trialkyl phosphate and a tri-alkyl phosphine oxide in an hydrocarbon diluent. By selecting an appropriate combination of pH and hydrogen peroxide content of the feed, contents of the components of the extraction composition and temperature of extraction, selective extraction of molybdenum can be obtained. In some particularly preferred embodiments, the feed pH is in the range of 0.85 to 1.5, the mole ratio of hydrogen peroxide to tungsten and molybdenum is 0.6 to 1.0, the temperature of extraction is in the range 12.degree. to 20.degree. C.