A mineral having composition FeSO₄·7H₂O. Melanterite occurs mainly in green, fibrous or concretionary masses or in short, monoclinic, prismatic crystals (see illus.). Fracture is conchoidal and luster is vitreous. Hardness is 2 on Mohs scale, and specific gravity 1.90. The mineral is similar to chalcanthite, has an astringent taste, and is readily soluble in water.