What is molybdates in mineralogy ?

Molybdates : definition

Molybdates are a subclass of the large mineralogical class of sulfates, chromates, molybdates and tungstates. The structure of molybdates is built on the same model as sulphates with groups (MoO4)2-, linked together by large cations of the Ca2+ or Pb2+ type. Molybdates are quite rare minerals, the most common being powellite (CaMoO4) and wulfenite (PbMoO4).

W and Mo have similar ionic radii and are easily replaced. There are therefore partial solid solutions between scheelite (CaWO4) and powellite (CaMoO4), on the one hand, and between stolzite (PbWO4) and wulfenite (PbMoO4), on the other hand. Lead and calcium also substituting themselves, one observes partial solid solutions "transverse" scheelite - stolzite and powellite - wulfenite.