IMA 2014-093 = polloneite

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Marco E. Ciriotti
Messaggi: 23496
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
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IMA 2014-093 = polloneite

Messaggio da Marco E. Ciriotti » ven 24 feb, 2017 11:22

Prossima pubblicazione.

Referenza:
▪ Topa, D., Keutsch, F.N., Makovicky, E., Kolitsch, U., Paar, W. (2017): Polloneite, a new complex Pb(-Ag)-As-Sb sulfosalt from the Pollone mine, Apuan Alps, Tuscany, Italy. Mineralogical Magazine, 81, (in press).

Abstract:
Polloneite, ideally AgPb46As26Sb23S120, is a new N = 4 member of the sartorite homologous series. It occurs in a matrix of baryte from the Pizzone level of the Pollone baryte–pyrite– (Pb–Zn–Ag) deposit at Valdicastello Carducci, near Pietrasanta, in the Apuan Alps, Tuscany, Italy, as anhedral grains up to 0.5 mm across.The mineral is opaque, greyish black with a metallic lustre. In reflected light polloneite is white, bireflectance is moderate. Internal reflections are absent. Under crossed polars, anisotropism is moderate with rotation tints in brown-violet and deep grey. The reflectance data (%, air) are: 30.2, 42.4 at 470 nm, 28.8, 41.0 at 546 nm, 27.9, 39.8 at 589 nm and 26.0, 37.4 at 650 nm. Mohs hardness is 3-3½, microhardness VHN50 exhibits a mean value of 200 kg mm-2. The average results of 15 electron-microprobe analyses of three grains are (s.u.s in parentheses): Ag 0.71(5), Pb 52.05(21), As 10.61(22), Sb 15.40(12), S 21.16(8), total 99.92(15) wt.%, corresponding to Ag1.20Pb45.76As25.79Sb23.04S120.21 (on the basis of Me + S = 216 apfu). The simplified formula AgPb46As26Sb23S120 is in accordance with the results of a crystal-structure determination. The calculated density is 5.77 g/cm3. Polloneite is monoclinic, space group P21, unit-cell parameters are a = 8.413(2) Å, b = 25.901(5) Å, c = 23.818(5) Å, and beta = 90.01(3)°, [V = 5189.8(18) Å3 and Z = 1. The strongest eight lines in the calculated powder-diffraction pattern [d in Å(I)hkl] are: 3.795(100)(026), 3.414(60)(233), 3.238(69)(080), 3.020(97)(253), 2.922(82)(066), 2.738(73)(236), 2.375(79)(290) and 2.103(64)(400). Polloneite is a new N = 4 member of the sartorite homologous series with substantial Sb and small, but important, Ag contents. It is a three-fold superstructure with a tripled unit-cell parameter 7.9 Å of the sartorite homologues. In the As-Sb rich slabs, several types of crankshaft chains and isolated (As,Sb)-S polyhedra occur. A sequence of three different, tightly-bonded double layer fragments (broad ribbons) contains two asymmetric fragments with long crankshaft chains whereas the third fragment type, with Ag, contains small mirror-symmetrical metalloid groups and no crankshaft chains. This configuration can potentially cause order-disorder phenomena in the structure. The threefold superstructure and the mixed As-Sb character distinguish polloneite from veenite and from dufrénoysite, respectively.
Marco E. Ciriotti

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

Avatar utente
Marco E. Ciriotti
Messaggi: 23496
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Re: IMA 2014-093 = polloneite

Messaggio da Marco E. Ciriotti » mar 31 ott, 2017 11:48

Pubblicazione avvenuta.

Referenza:
▪ Topa, D., Keutsch, F.N., Makovicky, E., Kolitsch, U., Paar, W. (2017): Polloneite, a new complex Pb(-Ag)-As-Sb sulfosalt from the Pollone mine, Apuan Alps, Tuscany, Italy. Mineralogical Magazine, 81, 1303-1322.

Abstract:
Polloneite, ideally AgPb46As26Sb23S120, is a new N = 4 member of the sartorite homologous series. It occurs in a matrix of baryte from the Pizzone level of the Pollone baryte–pyrite– (Pb–Zn–Ag) deposit at Valdicastello Carducci, near Pietrasanta, in the Apuan Alps, Tuscany, Italy, as anhedral grains up to 0.5 mm across.The mineral is opaque, greyish black with a metallic lustre. In reflected light polloneite is white, bireflectance is moderate. Internal reflections are absent. Under crossed polars, anisotropism is moderate with rotation tints in brown-violet and deep grey. The reflectance data (%, air) are: 30.2, 42.4 at 470 nm, 28.8, 41.0 at 546 nm, 27.9, 39.8 at 589 nm and 26.0, 37.4 at 650 nm. Mohs hardness is 3-3½, microhardness VHN50 exhibits a mean value of 200 kg mm-2. The average results of 15 electron-microprobe analyses of three grains are (s.u.s in parentheses): Ag 0.71(5), Pb 52.05(21), As 10.61(22), Sb 15.40(12), S 21.16(8), total 99.92(15) wt.%, corresponding to Ag1.20Pb45.76As25.79Sb23.04S120.21 (on the basis of Me + S = 216 apfu). The simplified formula AgPb46As26Sb23S120 is in accordance with the results of a crystal-structure determination. The calculated density is 5.77 g/cm3. Polloneite is monoclinic, space group P21, unit-cell parameters are a = 8.413(2) Å, b = 25.901(5) Å, c = 23.818(5) Å, and beta = 90.01(3)°, [V = 5189.8(18) Å3 and Z = 1. The strongest eight lines in the calculated powder-diffraction pattern [d in Å(I)hkl] are: 3.795(100)(026), 3.414(60)(233), 3.238(69)(080), 3.020(97)(253), 2.922(82)(066), 2.738(73)(236), 2.375(79)(290) and 2.103(64)(400). Polloneite is a new N = 4 member of the sartorite homologous series with substantial Sb and small, but important, Ag contents. It is a three-fold superstructure with a tripled unit-cell parameter 7.9 Å of the sartorite homologues. In the As-Sb rich slabs, several types of crankshaft chains and isolated (As,Sb)-S polyhedra occur. A sequence of three different, tightly-bonded double layer fragments (broad ribbons) contains two asymmetric fragments with long crankshaft chains whereas the third fragment type, with Ag, contains small mirror-symmetrical metalloid groups and no crankshaft chains. This configuration can potentially cause order-disorder phenomena in the structure. The threefold superstructure and the mixed As-Sb character distinguish polloneite from veenite and from dufrénoysite, respectively.
Marco E. Ciriotti

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