1) Monoclinic mineral 
Bílinite (Fe2+Fe23+(SO4)·22H2O) is an iron sulfate mineral. It is a product of the oxidation of pyrite in water. It is an acidic mineral that has a pH of less than 3 and is harmful to the environment when it comes from acid rock drainage (Keith et al., 2001). Bílinite was first discovered near Bílina, Czech Republic which is why the mineral wa...