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[3] and as a rare sublimate phase around volcanic fumaroles.[5] Associated minerals include pisanite, chalcanthite, epsomite, pickeringite, halotrichite and other sulfate minerals.[5]
Melanterite | |
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![]() Melanterite as found in nature | |
General | |
Category | Sulfate mineral |
Formula (repeating unit) | FeSO4·7H2O |
IMA symbol | Mln[1] |
Strunz classification | 7.CB.35 |
Dana classification | 29.06.10.01 |
Crystal system | Monoclinic |
Crystal class | Prismatic (2/m) (same H-M symbol) |
Space group | P21/c |
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 |
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 | [2][3][4][5] |
It was first described in 1850.[5]
Gallery
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Crystal structure of melanterite
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Cuprian melanterite
References
edit- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ Mineralienatlas
- ^ a b Mindat
- ^ Webmineral data
- ^ a b c d Handbook of Mineralogy