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Alluaudite

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Relatively common alkaline manganese iron phosphate mineral
Alluaudite
Alluaudite
General
CategoryPhosphate minerals
Formula
(repeating unit)		(Na,Ca)Mn(Fe,Mn,Fe,Mg)2(PO4)3
IMA symbolAld
Strunz classification8.AC.10
Dana classification38.2.3.6
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/c
Unit cella = 11.03 Å, b = 12.53 Å
c = 6.4 Å; β = 97.57°; Z = 4
Identification
ColorDirty yellow to brownish yellow, grayish green; superficially dull greenish black, brownish black, black, when altered
Crystal habitPlaty to radiating fibrous, nodular, granular, massive
TwinningPolysynthetic
CleavageDistinct/ good on {100} and {010}, good on {110}
Mohs scale hardness5 – 5.5
StreakBrownish yellow
DiaphaneityTranslucent
Specific gravity3.4 – 3.5
Optical propertiesBiaxial (+)
Refractive indexnα = 1.782 nβ = 1.802 nγ = 1.835
Birefringenceδ = 0.053
PleochroismX = pale olive-green, straw-yellow to greenish yellow; Z = pale olive-greenish to brownish yellow
2V angleMeasured: 50° to 90°, calculated: 78°
References

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

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). The mineral structure was first described in 1955.

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. ^ Alluaudite on Mindat.org
  3. ^ "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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