- Melanterite
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Melanterite General Category Sulfate mineral Chemical formula FeSO4·7H2O Strunz classification 07.CB.35 Dana classification 29.06.10.01 Crystal symmetry Monoclinic 2/m prismatic Unit cell a = 14.077 Å, b = 6.509 Å, c = 11.054 Å; β = 105.6°; Z = 4 Identification Color Green, pale green, greenish blue, bluish green, colorless Crystal habit Encrustations and capillary efflorescences; rarely as equant pseudo-octahedral, prismatic or tabular crystals Crystal system Monoclinic Cleavage {001} Perfect, {110} Distinct Fracture Conchoidal Mohs scale hardness 2 Luster Vitreous Streak White Diaphaneity Subtransparent to translucent Specific gravity 1.89 - 1.9 Optical properties Biaxial (+) Refractive index nα = 1.470 - 1.471 nβ = 1.477 - 1.480 nγ = 1.486 References [1][2][3] Melanterite is a mineral form of hydrous iron(II) sulfate: FeSO4·7H2O. It is the iron analogue of the copper sulfate chalcanthite. It alters to siderotil by loss of water. It is a secondary sulfate mineral which forms from the oxidation of primary sulfide minerals such as pyrite and marcasite in the near-surface environment. It often occurs as a post mine encrustation on old underground mine surfaces. It also occurs in coal and lignite seams exposed to humid air.[1] It also occurs as a rare sublimate phase around volcanic fumaroles.[3] Associated minerals include pisanite, chalcanthite, epsomite, pickeringite, halotrichite and other sulfate minerals.[3]
It was first described in 1850.[3]
References
- ^ a b http://www.mindat.org/min-2633.html Mindat
- ^ http://webmineral.com/data/Melanterite.shtml Webmineral data
- ^ a b c d http://rruff.geo.arizona.edu/doclib/hom/melanterite.pdf Handbook of Mineralogy
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