Crystal chemistry of johillerite

database, nuove specie, discrediti,
ridefinizioni, classificazioni, ecc.
Rispondi
Avatar utente
Marco E. Ciriotti
Messaggi: 24277
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Crystal chemistry of johillerite

Messaggio da Marco E. Ciriotti » mer 25 apr, 2018 11:04

Prossima pubblicazione.

Referenza:
▪ Koshlyakova, N.N., Zubkova, N.V., Pekov, I.V., Giester, G., Sidorov, E.G. (2018): Crystal chemistry of johillerite. Canadian Mineralogist, 56, (in press).

Abstract:
Johillerite, an anhydrous arsenate member of the alluaudite group with the idealized crystal chemical formula A(2)NaA(1)CuMMg3(TAsO4)3, is an abundant mineral in the exhalations of the Arsenatnaya fumarole on the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Kamchatka, Russia. Chemical variations of johillerite from Tolbachik were studied and the crystal structure was solved for three samples that represent different chemical varieties of the mineral. Johillerite forms a continuous solid-solution system with badalovite, Na2Mg2Fe3+(AsO4)3, and nickenichite, Na(□,Cu)(□,Ca)(Mg,Fe)3(AsO4)3, and a discontinuous solid solution with bradaczekite, NaCu4(AsO4)3. The major substitution schemes are: (1) MMg = MCu2+; (2) ACu2+ + M2+ = ANa+ + M3+; (3) ANa+ + M2+ = A□0 + M3+; and (4) ACu2+ + 2M2+ = A□0 + 2M3+. The T sites are occupied by As5+ with only minor admixtures of other constituents (P, V, S, Si).
Structurally studied johillerite crystals (monoclinic, C2/c) have the following crystal chemical formulae:
(1) A(2)′Na0.75A(1)′Cu0.85A(1)Na0.13M(1)(Mg0.91Fe0.09)M(2)(Mg1.60Fe0.34Cu0.06)(AsO4)3;
(2) A(2)′Na0.84A(1)′Cu0.68A(1)Na0.33M(1)(Mg0.68Zn0.32)M(2)(Mg0.90Cu0.62 Fe0.16Al0.08)(AsO4)3;
(3) A(2)′Na0.91A(1)′Cu0.98M(1)(Mg0.74Cu0.16Zn0.10)M(2)(Mg1.34Cu0.52Fe0.14)(AsO4)3.
Mg and Zn prefer the M(1)O6 octahedra rather than the M(2)O6, whereas Fe3+ and Al3+ mainly concentrate at the M(2) site.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

Avatar utente
Marco E. Ciriotti
Messaggi: 24277
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Re: Crystal chemistry of johillerite

Messaggio da Marco E. Ciriotti » lun 21 mag, 2018 22:34

Pubblicazione effettuata.

Referenza:
▪ Koshlyakova, N.N., Zubkova, N.V., Pekov, I.V., Giester, G., Sidorov, E.G. (2018): Crystal chemistry of johillerite. Canadian Mineralogist, 56, 189-201.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

Rispondi

Chi c’è in linea

Visitano il forum: Nessuno e 2 ospiti