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Alluaudite 
Summary
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]
| Alluaudite | |
|---|---|
 Alluaudite | |
| General | |
| Category | Phosphate minerals |
| Formula (repeating unit) | (Na,Ca)Mn2+(Fe3+,Mn2+,Fe2+,Mg)2(PO4)3 |
| IMA symbol | Ald[1] |
| Strunz classification | 8.AC.10 |
| Dana classification | 38.2.3.6 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | C2/c |
| Unit cell | a = 11.03 Å, b = 12.53 Å c = 6.4 Å; β = 97.57°; Z = 4 |
| Identification | |
| Color | Dirty yellow to brownish yellow, grayish green; superficially dull greenish black, brownish black, black, when altered |
| Crystal habit | Platy to radiating fibrous, nodular, granular, massive |
| Twinning | Polysynthetic |
| Cleavage | Distinct/ good on {100} and {010}, good on {110} |
| Mohs scale hardness | 5 – 5.5 |
| Streak | Brownish yellow |
| Diaphaneity | Translucent |
| Specific gravity | 3.4 – 3.5 |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 1.782 nβ = 1.802 nγ = 1.835 |
| Birefringence | δ = 0.053 |
| Pleochroism | X = pale olive-green, straw-yellow to greenish yellow; Z = pale olive-greenish to brownish yellow |
| 2V angle | Measured: 50° to 90°, calculated: 78° |
| References | [2][3][4] |
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 edit
- ^ 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.
- ^ a b Alluaudite on Mindat.org
- ^ a b c "Alluaudite in the Handbook of Mineralogy" (PDF). Archived from the original (PDF) on 2016-03-03. Retrieved 2009-12-21.
- ^ Alluaudite data on Webmineral
- ^ 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.