IMA 2011-077 = thermessaite-(NH4)

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Marco E. Ciriotti
Messaggi: 31675
Iscritto il: ven 25 giu, 2004 11:31
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IMA 2011-077 = thermessaite-(NH4)

Messaggio da Marco E. Ciriotti » mer 01 set, 2021 20:46

Prossima pubblicazione.

Referenza:
▪ Garavelli, A., Pinto, D., Mitolo, D., Kolitsch, U. (2021): Thermessaite-(NH4), (NH4)2AlF3(SO4), a new fumarole mineral from La Fossa crater at Vulcano, Aeolian Islands, Italy. Mineralogical Magazine, 85, (in press).

Abstract:
Thermessaite-(NH4), ideally (NH4)2AlF3(SO4), is a new mineral found as a medium- to high-temperature (about 250-300°C) fumarole encrustation at the rim of La Fossa crater, Vulcano, Aeolian Islands, Italy. The mineral deposited as aggregates of micrometer-sized sharp prismatic crystals on the surface of a pyroclastic breccia in association with thermessaite, sulfur, arcanite, mascagnite, and intermediate members of the arcanite-mascagnite series.
The new mineral is colorless to white, transparent, non-fluorescent, has a vitreous luster, and a white streak. The calculated density is 2.185 g/cm3. Thermessaite-(NH4) is orthorhombic, space group Pbcn, with a = 11.3005(3) Å, b = 8.6125(3) Å, c = 6.8501(2) Å, V = 666.69(4) Å3, Z = 4. The eight strongest reflections in the X-ray powder-diffraction data [d in Å (I) (hkl)] are: 5.65 (100) (200), 4.84 (89) (111), 6.85 (74) (110), 3.06 (56) (112), 3.06 (53) (221), 3.08 (47) (311), 2.68 (28) (022), 2.78 (26) (130). The average chemical composition, determined by quantitative SEM-EDS (N by difference), is (wt%): K2O 3.38, Al2O3 25.35, SO3 36.58, F 26.12, (NH4)2O 22.47, O = F -11.00, total 102.90. The empirical chemical formula, calculated on the basis of 7 anions pfu, is [(NH4)1.85K0.15]Σ2.00Al106F2.94-S0.98O3.06. The crystal structure, determined from single-crystal X-ray diffraction data [R(F) = 0.0367], is characterized by corner-sharing AlF4O2 octahedra which form [001] octahedral chains by sharing two trans fluoride atoms [Al–F2 = 1.8394(6) Å]. Non-bridging Al–F1 distances are shorter [1.756(1) Å]. The two trans oxygen atoms [Al–O = 1.920(2) Å] are from SO4 tetrahedra. NH4+ ions occur in layers parallel to (100) which alternate regularly with (100) layers containing ribbons of corner-sharing AlF4O2 octahedra and associated SO4 groups. The NH4+ ions are surrounded by five oxygen atoms and by four fluorine atoms. The mineral is named as the (NH4)-analogue of thermessaite, K2AlF3(SO4), and corresponds to an anthropogenic phase found in the burning Anna I coal dump of the Anna mine, Aachen, Germany. Both mineral and mineral name have been approved by the IMA-CNMNC commission (IMA 2011-077).
Marco E. Ciriotti

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

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Marco E. Ciriotti
Messaggi: 31675
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Re: IMA 2011-077 = thermessaite-(NH4)

Messaggio da Marco E. Ciriotti » ven 26 nov, 2021 15:32

Pubblicazione effettuata.

Referenza:
▪ Garavelli, A., Pinto, D., Mitolo, D., Kolitsch, U. (2021): Thermessaite-(NH4), (NH4)2AlF3(SO4), a new fumarole mineral from La Fossa crater at Vulcano, Aeolian Islands, Italy. Mineralogical Magazine, 85, 665-672.
Marco E. Ciriotti

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

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