Vanadanite is Pb5(VO4)3Cl, Lead chloro vanadate. belonging to the apatite group of phosphates. It is a secondary mineral found in the oxidising zone of lead deposits. In the crystal lattice, vanadium can be substituted by phosphorus or arsenic, for instance Mimetite is Pbs(AsO4)3Cl , and there is a series betwen the two minerals. This specimen is from the Apache mine, in Arizona, USA.