Ferric tellurite, Fe(TeO₃)₃

Ferric tellurite occurs in nature as the mineral durdenite in Honduras, associated with metallic tellurium. Hardness 2 to 2.5. Its chemical composition closely approaches that represented by the formula Fe₂O₃.3TeO₂.4H₂O, or Fe(TeO₃)₃.4H₂O. Emmonsite is another naturally occurring ferric tellurite found in Colorado as yellowish green scales, associated with lead carbonate and quartz.