IMA 2018-017 = jahnsite-(NaMnMg)

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Marco E. Ciriotti
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IMA 2018-017 = jahnsite-(NaMnMg)

Messaggio da Marco E. Ciriotti » ven 21 dic, 2018 11:49

Prossima pubblicazione.

Referenza:
▪ Kampf, A.R., Elliott, P., Nash, B.P., Chiappino, L., Varvello, S. (2018): Jahnsite-(NaMnMg), a New Jahnsite-Group Mineral from the Sapucaia Mine, Brazil and the White Rock No. 2 Quarry, Australia. Canadian Mineralogist, 56, (in press).

Abstract:
Jahnsite-(NaMnMg), (Na,Ca)(Mn2+,Fe3+)(Mg,Fe3+,Mn3+)2Fe3+2(PO4)4(OH)2(H2O)8, is a new mineral from the Sapucaia pegmatite, Conselheiro Pena pegmatite district, Minas Gerais, Brazil, and the White Rock No. 2 quarry, Bimbowrie Conservation Park, South Australia, Australia. At both localities, it is a low temperature, secondary mineral formed as the result of alteration of primary phosphates. The mineral occurs as light orange to orange-yellow prisms, elongate on [100], exhibiting the forms {100}, {001}, and {011} and twinned by reflection on {001}. The streak is white, the luster is vitreous, and crystals are transparent to translucent. The Mohs hardness is about 4. The tenacity is brittle, the fracture is irregular, stepped (splintery), and there is one very good cleavage on {001}. The measured density is 2.68(1) g/cm3 (Sapucaia). The mineral is slowly soluble in dilute HCl. Jahnsite-(NaMnMg) from Sapucaia is biaxial (–), with α 1.642(1), β 1.675(1), γ 1.677(1) (white light). The measured 2V is 29(1)°. Dispersion is very strong, r < v. The optical orientation is Z = b; X ^ c = 51° in obtuse β. Pleochroism is X = colorless, Y and Z = orange-yellow; Y ≈ Z > X. Electron-microprobe analyses gave the empirical formulae (Na0.56Ca0.25Mn2+0.09)Σ0.90(Mn2+0.85Fe3+0.15)Σ1.00(Mg1.53Fe3+0.47)Σ2.00(Fe3+1.79Al0.21)Σ2(PO4)4(OH)1.83(H2O)8.17 for the Sapucaia material and (Na0.63Ca0.23Mn2+0.14)Σ1.00(Mn2+0.68Mn3+0.26Fe3+0.05Mg0.01)Σ1.00(Mg1.26Mn2+0.43Mn3+0.16Fe3+0.15)Σ2.00(Fe3+1.97Al0.02)Σ1.99(PO4)4(OH)1.98(H2O)8.02 for the White Rock material. The mineral is monoclinic, space group P2/a, with cell parameters (Sapucaia) a 15.1045(15), b 7.1629(2), c 9.8949(7) Å, β 110.640(7)°, V 1001.83(13) Å3, and Z = 2. The structure refinements of crystals from both localities were generally consistent and showed the mineral to be a member of the jahnsite group (Sapucaia: R1 = 3.19% for 1941 Io > 2σI reflections; White Rock: R1 = 6.94% for 13485 Io > 2σI reflections).
Marco E. Ciriotti

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Marco E. Ciriotti
Messaggi: 25117
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
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Re: IMA 2018-017 = jahnsite-(NaMnMg)

Messaggio da Marco E. Ciriotti » gio 31 gen, 2019 11:19

Pubblicazione effettuata.

Referenza:
▪ Kampf, A.R., Elliott, P., Nash, B.P., Chiappino, L., Varvello, S. (2018): Jahnsite-(NaMnMg), a New Jahnsite-Group Mineral from the Sapucaia Mine, Brazil and the White Rock No. 2 Quarry, Australia. Canadian Mineralogist, 56, 871-882.
Marco E. Ciriotti

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TOSATO FABIO
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Re: IMA 2018-017 = jahnsite-(NaMnMg)

Messaggio da TOSATO FABIO » ven 01 feb, 2019 6:54

Complimenti agli autori e a chi ha scoperto il nuovo minerale.
Tosato Fabio
"Il vero viaggio di scoperta non consiste nel cercare nuove terre, ma nell'avere nuovi occhi." M. Proust
Noi siamo anche quello che non siamo riusciti ad essere.
Sic transit gloria mundi.

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