The new mineral campostriniite, (Bi3+,Na)3(NH4,K)2Na2(SO4)6·H2O, was found in an active fumarole (fumarole FA, temperature ~350ºC) at La Fossa Crater, Vulcano, Aeolian Islands, Sicily, Italy. It occurs on a pyroclastic breccia as white prismatic crystals up to 0.2 mm long, in association with adranosite, demicheleite-(Br), demicheleite-(I), argesite and sassolite. The mineral is monoclinic, space group: C2/c (no. 15) with a = 17.748(3), b = 6.982(1) c = 18.221(3) A ˚ , b = 113.97(1)º, V = 2063(1) A ˚ 3 and Z = 4. The six strongest reflections in the powder X-ray diffraction pattern are: [dobs in A ˚ (I)(hkl)] 6.396(100)(110), 7.507(75)(2¯ 02), 2.766(60)(3¯16), 3.380(57)(312), 5.677(55)(111), 3.166(50)(4 0 2). The empirical formula (based on 25 anions p.f.u.) is Bi2.41N1.52Na2.41K0.48 S6.07H8.08O25. The calculated density is 3.87 g cm3. Using single-crystal diffraction data, the structure was refined to a final R(F) = 0.051 for 3025 independent observed reflections [I > 2s(I)]. Campostriniite is isostructural with go¨rgeyite and belongs to the 7.CD group of the Strunz classification system. The structure contains two independent nine-fold coordinated sites, one of them located on a two-fold axis (M1) and the other one in general position (M2) essentially occupied by Bi3+ atoms and minor amounts of Na+ ions, an eight-fold coordinated site fully occupied by Na+ ions and another eight-fold coordinated site occupied by NH4 + and K+ ions; three independent sulfate anions in a general position and a water molecule coordinated to M1 and located on a two-fold axis are also present.

Campostriniite, (Bi3+,Na)3(NH4,K)2Na2(SO4)6·H2O, a new sulfate isostructural with gorgeyite, from La Fossa Crater, Vulcano, Aeolian Islands, Italy / F. Demartin, C. Castellano, C.M. Gramaccioli. - In: MINERALOGICAL MAGAZINE. - ISSN 0026-461X. - 79:4(2015 Aug), pp. 1007-1018. [10.1180/minmag.2015.079.4.10]

Campostriniite, (Bi3+,Na)3(NH4,K)2Na2(SO4)6·H2O, a new sulfate isostructural with gorgeyite, from La Fossa Crater, Vulcano, Aeolian Islands, Italy

F. Demartin;C. Castellano;C.M. Gramaccioli
2015-08

Abstract

The new mineral campostriniite, (Bi3+,Na)3(NH4,K)2Na2(SO4)6·H2O, was found in an active fumarole (fumarole FA, temperature ~350ºC) at La Fossa Crater, Vulcano, Aeolian Islands, Sicily, Italy. It occurs on a pyroclastic breccia as white prismatic crystals up to 0.2 mm long, in association with adranosite, demicheleite-(Br), demicheleite-(I), argesite and sassolite. The mineral is monoclinic, space group: C2/c (no. 15) with a = 17.748(3), b = 6.982(1) c = 18.221(3) A ˚ , b = 113.97(1)º, V = 2063(1) A ˚ 3 and Z = 4. The six strongest reflections in the powder X-ray diffraction pattern are: [dobs in A ˚ (I)(hkl)] 6.396(100)(110), 7.507(75)(2¯ 02), 2.766(60)(3¯16), 3.380(57)(312), 5.677(55)(111), 3.166(50)(4 0 2). The empirical formula (based on 25 anions p.f.u.) is Bi2.41N1.52Na2.41K0.48 S6.07H8.08O25. The calculated density is 3.87 g cm3. Using single-crystal diffraction data, the structure was refined to a final R(F) = 0.051 for 3025 independent observed reflections [I > 2s(I)]. Campostriniite is isostructural with go¨rgeyite and belongs to the 7.CD group of the Strunz classification system. The structure contains two independent nine-fold coordinated sites, one of them located on a two-fold axis (M1) and the other one in general position (M2) essentially occupied by Bi3+ atoms and minor amounts of Na+ ions, an eight-fold coordinated site fully occupied by Na+ ions and another eight-fold coordinated site occupied by NH4 + and K+ ions; three independent sulfate anions in a general position and a water molecule coordinated to M1 and located on a two-fold axis are also present.
campostriniite; new mineral species; crystal structure; bismuth sulfate; Vulcano Island; Italy
Settore CHIM/03 - Chimica Generale e Inorganica
Settore GEO/06 - Mineralogia
2015
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/335953
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