Ferrimolybdite

(repeating unit)Fe3+2(MoO4)3·8(H2O) or Fe3+2(MoO4)3·n(H2O)IMA symbolFmyb[1]Strunz classification7.GB.30Crystal systemOrthorhombicCrystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)Space groupPmmnUnit cella = 6.665, b = 15.423
c = 29.901 [Å]; Z = 8IdentificationColorCanary-yellow, straw-yellow, greenish yellowCrystal habitAcicular tufted to radial aggregates; powdery, earthyCleavageDistinct on {001}FractureUnevenMohs scale hardness1-2LusterAdamantine, silky, earthyStreakLight yellowDiaphaneityTransparent to translucentSpecific gravity2.99Optical propertiesBiaxial (+)Refractive indexnα = 1.720 - 1.810 nβ = 1.730 - 1.830 nγ = 1.850 - 2.040Birefringenceδ = 0.130 - 0.230PleochroismX = Y = clear to nearly colorless; Z = dirty gray to canary-yellow2V 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

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

  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
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