{{Short description|Relatively common alkaline manganese iron phosphate mineral}} {{Infobox mineral | name = Alluaudite | image = Alluaudite 2 Sodium iron manganese phosphate Pleasant Valley Mine near Fourmile Custer County South Dakota 2264Spp.jpg | alt = | caption = Alluaudite | category = Phosphate minerals | formula = {{chem2|(Na,Ca)Mn^{2+}(Fe^{3+},Mn^{2+},Fe^{2+},Mg)2(PO4)3}} |IMAsymbol=Ald<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref> | molweight = | strunz = 8.AC.10 | dana = 38.2.3.6 | system = Monoclinic | class = Prismatic (2/m) <br/><small>(same H-M symbol)</small> | symmetry = ''C2/c'' | unit cell = a = 11.03 Å, b = 12.53 Å <br/>c = 6.4 Å; β = 97.57°; Z = 4 | color = Dirty yellow to brownish yellow, grayish green; superficially dull greenish black, brownish black, black, when altered | habit = Platy to radiating fibrous, nodular, granular, massive | twinning = Polysynthetic | cleavage = Distinct/ good on {100} and {010}, good on {110} | fracture = | tenacity = | mohs = 5 – 5.5 | luster = | streak = Brownish yellow | diaphaneity = Translucent | gravity = 3.4 – 3.5 | density = | polish = | opticalprop = Biaxial (+) | refractive = n<sub>α</sub> = 1.782 n<sub>β</sub> = 1.802 n<sub>γ</sub> = 1.835 | birefringence = δ = 0.053 | pleochroism = X = pale olive-green, straw-yellow to greenish yellow; Z = pale olive-greenish to brownish yellow | 2V = Measured: 50° to 90°, calculated: 78° | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | references = <ref name=Mindat/><ref name=HBM/><ref>[http://www.webmineral.com/data/Alluaudite.shtml#.VTekNNK6fRY Alluaudite data on Webmineral]</ref> }}
'''Alluaudite''' is a relatively common alkaline manganese iron phosphate mineral with the chemical formula {{chem2|(Na,Ca)Mn^{2+}(Fe^{3+},Mn^{2+},Fe^{2+},Mg)2(PO4)3}}. It occurs as metasomatic replacement in granitic pegmatites and within phosphatic nodules in shales.<ref name=HBM/>
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).<ref name=Mindat>[http://www.mindat.org/min-142.html Alluaudite on Mindat.org]</ref><ref name=HBM>{{Cite web |url=http://www.handbookofmineralogy.org/pdfs/alluaudite.pdf |title=Alluaudite in the Handbook of Mineralogy |access-date=2009-12-21 |archive-date=2016-03-03 |archive-url=https://web.archive.org/web/20160303205227/http://www.handbookofmineralogy.org/pdfs/alluaudite.pdf |url-status=dead }}</ref> The mineral structure was first described in 1955.<ref>{{Cite journal |last1=Nowagiel |first1=Maciej |last2=Samsel |first2=Mateusz J. |last3=Pietrzak |first3=Tomasz K. |date=2021-09-01 |title=Towards the High Phase Purity of Nanostructured Alluaudite-Type Glass-Ceramics Cathode Materials for Sodium Ion Batteries |journal=Materials |volume=14 |issue=17 |pages=4997 |doi=10.3390/ma14174997 |pmc=8434363 |pmid=34501086|bibcode=2021Mate...14.4997N |doi-access=free }}</ref>
==References== {{Reflist}}
Category:Phosphate minerals Category:Manganese(II) minerals Category:Iron(II,III) minerals Category:Sodium minerals Category:Monoclinic minerals Category:Minerals in space group 15 Category:Minerals described in 1848
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