Tetrahedrite is a copper sulfosalt mineral with formula: (Cu,Fe) 12Sb 4S 13. It is the antimony endmember of the continuous solid solution -bearing tennantite. Pure endmembers of the series are seldom if ever seen in nature. Of the two, the antimony rich phase is more common. Other elements also substitute in the structure, most notably iron and zinc, along with less common silver, mercury and lead. Bismuth also substitutes for the antimony site and bismuthian tetrahedrite or annivite is a recognized variety. The related, silver dominant, mineral species freibergite , although rare, is notable in that it can contain up to 18% silver.