Melanterite is a hydrated iron sulphate formed after the decomposition mostly of pyrite due to the interaction of surface waters. After moisture season, especial during the spring time, due drying process the melanterite could be found as an efflorescence on the surface of dried wall rocks with higher content of iron minerals.  Fresh crystalized melanterite looks than very similar as a blue-green algae and could be mistaken for it. Often appears in mines as a post mining secondary formation on mine walls. Melanterite dissolve easy in water and disintegrate fast in hot climate.   

Synonyms: Copperas, Green Vitriol, Iron Vitriol, Melantherite, Sulphate of Iron
Classification: Suphate
Chemical formula: Fe[SO4]·7H2O
Crystal system: Monoclinic
Density (g/cm3): 1.895 - 1,898 measured, 1,897 calculated
Tenacity: Brittle
Cleavage: Perfect on {001}, distinct on {110}
Fracture: Conchoidal
Hardness (Mohs): 2
Colour: Colorless to white or green, also greenish-blue to blue with increased Cu content
Lustre: Vitreous
Streak: White
Transparency: Translucent, Opaque
For the production of colors for wool and leather as well as for ink