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Ferrimolybdite

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Ferrimolybdite
Ferrimolybdite crystals from the Kingman District, Mohave County, Arizona
General
CategoryMolybdate mineral
Formula
(repeating unit)
Fe3+2(MoO4)3·8(H2O) or Fe3+2(MoO4)3·n(H2O)
IMA symbolFmyb[1]
Strunz classification7.GB.30
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupPmmn
Unit cella = 6.665, b = 15.423
c = 29.901 [Å]; Z = 8
Identification
ColorCanary-yellow, straw-yellow, greenish yellow
Crystal habitAcicular tufted to radial aggregates; powdery, earthy
CleavageDistinct on {001}
FractureUneven
Mohs scale hardness1-2
LusterAdamantine, silky, earthy
StreakLight yellow
DiaphaneityTransparent to translucent
Specific gravity2.99
Optical propertiesBiaxial (+)
Refractive indexnα = 1.720 - 1.810 nβ = 1.730 - 1.830 nγ = 1.850 - 2.040
Birefringenceδ = 0.130 - 0.230
PleochroismX = Y = clear to nearly colorless; Z = dirty gray to canary-yellow
2V angle26° to 32° (calculated)
References[2][3][4]

Ferrimolybdite is a hydrous iron molybdate mineral with formula: Fe3+2(MoO4)3·8(H2O)[3] or Fe3+2(MoO4)3·n(H2O).[2] It forms coatings and radial aggregates of soft yellow needles which crystallize in the orthorhombic system.

Discovery and occurrence

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It was first described in 1914 for an occurrence in the Alekseevskii Mine in the Karysh River Basin, Khakassia Republic, Siberia, Russia.[2] It was named for its composition (ferric iron and molybdenum).

It occurs as an oxidation product of molybdenum bearing ore deposits. Associated minerals include: molybdenite, pyrite and chalcopyrite.[3]

References

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  1. ^ 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.
  2. ^ a b c Ferrimolybdite on Mindat.org
  3. ^ a b c Ferrimolybdite on the Handbook of Mineralogy
  4. ^ Ferrimolybdite data on Webmineral.com