Alluaudite

(Na,Ca)Mn2+(Fe3+,Mn2+,Fe2+,Mg)2(PO4)3IMA symbolAld[1]Strunz classification8.AC.10Dana classification38.2.3.6Crystal systemMonoclinicCrystal classPrismatic (2/m)
(same H-M symbol)Space groupC2/cUnit cella = 11.03 Å, b = 12.53 Å
c = 6.4 Å; β = 97.57°; Z = 4IdentificationColorDirty yellow to brownish yellow, grayish green; superficially dull greenish black, brownish black, black, when alteredCrystal habitPlaty to radiating fibrous, nodular, granular, massiveTwinningPolysyntheticCleavageDistinct/ good on {100} and {010}, good on {110}Mohs scale hardness5 – 5.5StreakBrownish yellowDiaphaneityTranslucentSpecific gravity3.4 – 3.5Optical propertiesBiaxial (+)Refractive indexnα = 1.782 nβ = 1.802 nγ = 1.835Birefringenceδ = 0.053PleochroismX = pale olive-green, straw-yellow to greenish yellow; Z = pale olive-greenish to brownish yellow2V angleMeasured: 50° to 90°, calculated: 78°References[2][3][4]

Alluaudite is a relatively common alkaline manganese iron phosphate mineral with the chemical formula (Na,Ca)Mn2+(Fe3+,Mn2+,Fe2+,Mg)2(PO4)3. It occurs as metasomatic replacement in granitic pegmatites and within phosphatic nodules in shales.[3]

It was first described in 1848 for an occurrence in Skellefteå, Västerbotten, Sweden. It was named by Alexis Damour after François Alluaud (II) (1778–1866).[2][3] The mineral structure was first described in 1955.[5]

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 Alluaudite on Mindat.org
  3. ^ a b c "Alluaudite in the Handbook of Mineralogy" (PDF). Archived from the original (PDF) on 2016-03-03. Retrieved 2009-12-21.
  4. ^ Alluaudite data on Webmineral
  5. ^ Nowagiel, Maciej; Samsel, Mateusz J.; Pietrzak, Tomasz K. (2021-09-01). "Towards the High Phase Purity of Nanostructured Alluaudite-Type Glass-Ceramics Cathode Materials for Sodium Ion Batteries". Materials. 14 (17): 4997. Bibcode:2021Mate...14.4997N. doi:10.3390/ma14174997. PMC 8434363. PMID 34501086.
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