Italo Campostrini

Structure of the new mineral sarrabusite, Pb5CuCl4(SeO3)4, solved by manual electron-diffraction tomography

The new mineral sarrabusite Pb(5)CuCl(4)(SeO(3))(4) has been discovered in the Sardinian mine of Baccu Locci, near Villaputzu. It occurs as small lemon-yellow spherical aggregates of tabular crystals (< 10 µm) of less than 100 µm in diameter. The crystal structure has been solved from and refined against electron diffraction of a microcrystal. Data sets have been measured by both a manual and an automated version of the new electron-diffraction tomography technique combined with the precession of the electron beam. The sarrabusite structure is monoclinic and consists of (010) layers of straight chains formed by alternating edge-sharing CuO(4)Cl(2) and PbO(8) polyhedra parallel to the c axis, which share corners laterally with two zigzag corner-sharing chains of PbO(6)Cl(2) and PbO(4)Cl(4) bicapped trigonal prisms. These blocks are linked together by SeO(3)(2-) flat-pyramidal groups.

Demicheleite-(Cl), BiSCl, a new mineral from La Fossa crater, Vulcano, Aeolian Islands, Italy

Abstract Demicheleite, ideally BiSBr, is the first natural bismuth sulfohalogenide so far discovered. It is identical with the corresponding and analogous synthetic compound and is one of the very few minerals where bromine is an essential component. It was found in an active high-temperature fumarole at the rim of La Fossa crater, Vulcano Island, Aeolian archipelago, Sicily, Italy. The mineral occurs as prismatic translucent crystals up to 0.5 mm in size in an altered pyroclastic breccia, together with pseudocotunnite, bismoclite, bismuthinite, cotunnite, and challacolloite. The mineral is orthorhombic, space group Pnam, with a = 8.0424(9), b = 9.8511(11), and c = 4.0328(5) Å, V = 319.50(6) Å3, Z = 4 (from single crystal); the habit is prismatic with {110} and {210} as prevailing forms, terminated by minor faces of another prism {011}, a pinacoid {010}, and a bipyramid {111}.The color is dark red to black; the streak is red; the luster submetallic. Non-fluorescent. Tenacity: brittle. Cleavage and fracture: not observed. The calculated density is 6.312 g/cm3. The chemical analysis obtained by EDS microprobe gave (wt%) Bi 67.6(4), Br 17.4(7), Cl 4.1(4), I 0.6(1), S 10.1(1), total 99.8, corresponding to the empirical formula (based on 3 apfu): Bi0.99S0.97(Br0.67Cl0.35I0.02)Σ=1.04 The crystal structure has been refined to a final R index of 0.037 and contains Bi in sevenfold coordination at the center of a monocapped trigonal prism. By sharing the triangular bases, such polyhedra form rows extending along [001]. These rows are connected to symmetry-related rows by sharing S-S edges of the pyramidal caps; these double rows are connected to each other by sharing Br/Cl atoms. The bond lengths are close to those of the synthetic counterparts BiSBr and BiSCl, with Bi-S bonds 2.593(3) and 2.720(2) Å long and Bi-Br/Cl bonds 3.009(1) and 3.488(2) Å long. The strongest 6 lines in the X-ray powder diffraction pattern [dobs(Å) (I) hkl] are: 4.220 (68) (120), 3.740 (62) (210), 2.909 (100) (121), 2.036 (47) (321), 1.865 (63) (022), and 1.774 (88) (411). The mineral is named after Vincenzo de Michele (b. 1936), former curator of the Section of Mineralogy of the Museo di Storia Naturale, Milano, Italy. Both the mineral and the mineral name have been approved by the IMA Commission on New Minerals, Nomenclature and Classification (IMA 2007-022). The type specimen is deposited (no. 2007-1) in the Reference Collection of Dipartimento di Chimica Strutturale e Stereochimica Inorganica of Università degli Studi di Milano.

Aiolosite, Na2(Na2Bi)(SO4)3Cl, a new sulfate isotypic to apatite from La Fossa Crater, Vulcano, Aeolian Islands, Italy

Abstract Aiolosite, ideally Na4Bi(SO4)3Cl, or better Na2(Na2Bi)(SO4)3Cl, is a new sulfate mineral isotypic to apatite. It was found in an active medium-temperature intracrater fumarole at La Fossa crater, Vulcano Island, Aeolian archipelago, Sicily, Italy. It occurs as acicular to slender prismatic crystals up to 0.5 mm long in an altered pyroclastic breccia, together with alunite, anhydrite, demicheleite-(Br), demicheleite-(Cl), bismuthinite, and panichiite. The symmetry is hexagonal (class 6/m), space group P63/m, with a = 9.626(3), c = 6.880(3) Å, V = 552.1(3) Å3, Z = 2. The habit is prismatic, terminated by the pinacoid or, more rarely, by a bipyramid. Aiolosite is colorless to white, with white streak; the luster vitreous. It is non-fluorescent. The calculated density is 3.589 g/cm3. The mineral is nonpleochroic, uniaxial (+), nω = 1.59(1), nε = 1.60(1), mean nobs = 1.593 (589 nm), ncalc = 1.620. The chemical analysis gave Na2O 20.65, K2O 0.96, Bi2O3 32.49, SO3 41.27, Cl 4.02, Br 0.75, (H2O 0.57 from structure refinement), -O = (Cl + Br) 0.98 wt%, total 99.73, corresponding to the empirical formula calculated on the basis of 13 anions: Na2(Na1.95K0.12Bi3+0.83)Σ2.90S3.06O12.08[Cl0.67Br0.06(H2O)0.19]Σ0.92. The crystal structure has been refined to a final R index of 0.048. One of the two independent Ca sites of apatite is exclusively occupied by Na, and the other one by statistically distributed Na and Bi. The SO42- anion replaces the PO43- anion of apatite; the chloride anion is located in the partially occupied (s.o.f. = 0.81) position at x = 0, y = 0, z = 0. Whenever the chloride position is vacant, the position at x = 0, y = 0, z = 1/4 is occupied by water (s.o.f. = 0.19). The strongest 6 lines in the X-ray powder diffraction pattern [dobs (Å) (I) hkl] are: 2.853 (100) (121), 2.775 (85) (112), 3.432 (45) (002), 1.965 (35) (222), 2.306 (25) (310), 4.787 (20) (110). Both the mineral and the mineral name have been approved by the IMA CNMNC (No. 2008-015).

Demicheleite-(I), BiSI, a new mineral from La Fossa Crater, Vulcano, Aeolian Islands, Italy

Abstract Demicheleite-(I), ideally BiSI, is the iodine-dominant analogue of demicheleite-(Br) and demicheleite-(Cl). It was found in an active medium-temperature intracrateric fumarole at La Fossa crater, Vulcano Island, Aeolian archipelago, Sicily, Italy. The mineral is the first bismuth sulphoiodide so far discovered in a wholly natural environment, and corresponds to the already known synthetic compound. It occurs as acicular to stout, translucent crystals up to 0.25 mm long in an altered pyroclastic breccia, together with demicheleite-(Br), bismoclite, bismuthinite, godovikovite, panichiite, aiolosite, brontesite, adranosite and other new phases under study. The colour is dark red to black, the lustre submetallic. The unit cell is orthorhombic, space group Pnam, with a = 8.4501(7) Å, b = 10.1470(9) Å, c = 4.1389(4) Å, V = 354.88(4) Å3, and Z = 4. The crystal habit is prismatic, with the main forms {110} and {111} inferred from analogy with demicheleite-(Br). Twinning was not observed. The strongest 6 lines in the X-ray powder diffraction pattern [dobs.(Å) (I/I0) (hkl)] are: 6.490 (100) (110); 4.346 (94) (120); 3.896 (90) (210); 2.709 (60) (310); 2.161 (38) (330); 3.243 (22) (220). The chemical analysis obtained by WDS electron microprobe gave: Bi 58.32, S 9.43, I 23.69, Br 5.66, Cl 1.01, totalling 98.11 wt.%, corresponding to an empirical formula (based on 3 a.p.f.u.) of: Bi0.97S1.03(I0.65Br0.25Cl0.10)∑1.00. The unit-cell data are close to those of the synthetic compound, whose crystal structure is already known. The calculated density is 6.411 g cm-3.

Lead-antimony sulfosalts from Tuscany (Italy). IX. Marrucciite, Hg3Pb16Sb18S46, a new sulfosalt from Buca della Vena mine, Apuan Alps: Definition and crystal structure

Marrucciite, Hg 3 Pb 16 Sb 18 S 46 , is a new sulfosalt discovered in the Fe-Ba deposit of Buca della Vena, Apuan Alps (Italy). It occurs as black acicular metallic crystals in calcite veins; reflectance values in air are (R %, λ nm): 33.1 ( 470 ), 30.0 ( 546 ), 28.8 ( 589 ), 26.5 ( 650 ). Marrucciite is monoclinic, space group C 2/ m , with a 48.32(1) A, b 4.117(1) A, c 24.056(5) A, β 118.84(3)°, V 4192(3) A 3 , Z = 2, D calc. = 6.00 g/cm 3 ; a 2 b superstructure is present. Main lines of the X-ray diffraction powder pattern [d (in A), I (main hkl)]: 4.02, 33 (12.0.3, 802); 3.480, 64 (803, 604); 3.418, 88 (607, 10.0.2, 314) ; 3.106, 31 (9.1.4); 2.994, 100 (11.1.2); 2.922, 41 (11.1.1); 2.056, 52 (020); 1.764, 41 (627). Electron microprobe analysis gave (wt.%; mean of 4 spot analyses): Cu 0.18(12), Hg 7.90(9), Pb 42.41(7), Sb 29.71(7), S 19.47(18), Cl 0.06(2), sum 99.73(14). The chemical formula (basis: 46 (S + Cl) at.) is Cu 0.21 Hg 2.98 Pb 15.46 Sb 18.44 S 45.87 Cl 0.13 , giving the stoichiometric one Hg 3 Pb 16 Sb 18 S 46 that fulfils the charge balance. X-ray single crystal study (R = 9.56 %) revealed a complex structure, with Hg in two specific distorted octahedral coordinations (2 short distances each, close to 2.36 A). There are 40 other independent positions: 7 Pb, 2 (Pb,Sb), 8 Sb and 23 S. The general architecture of the structure is strongly related to that of hexagonal Ba 12 Bi 24 S 48 , with three types of Me 10 S 14 rods (× 2) around a HgSb 2 Pb 4 S 4 central column. It explains the pseudo-hexagonal symmetry ( a /2 ~ c ; β ~ 120°). A strong topologic relationship exists also between marrucciite and scainiite. Like rouxelite, the other coexisting Hg bearing sulfosalt, marrucciite was formed by hydrothermal process during the Apenninic tectono-metamorphic event.

New minerals and nomenclature modifications approved in 2013 (IMA-CNMNC Newsletter 18)

P. A. WILLIAMS (Chairman, CNMNC), F. HATERT (Vice-Chairman, CNMNC), M. PASERO (Vice-Chairman, CNMNC) AND S. J. MILLS (Secretary, CNMNC) 1 School of Science and Health, University of Western Sydney, Locked Bag 1797, Penrith, NSW 2751, Australia p.williams@uws.edu.au 2 Laboratoire de Minéralogie, Université de Liège, B-4000 Liège, Belgium fhatert@ulg.ac.be 3 Dipartimento di Scienze della Terra, Università degli Studi di Pisa, Via Santa Maria 53, I-56126 Pisa, Italy marco.pasero@unipi.it 4 Geosciences, Museum Victoria, PO Box 666, Melbourne, Victoria 3001, Australia smills@museum.vic.gov.au

Aluminopyracmonite, (NH4)3Al(SO4)3, a new ammonium aluminium sulfate from La Fossa crater, Vulcano, Aeolian Islands, Italy

Abstract The new mineral aluminopyracmonite, ideally (NH4)3Al(SO4)3, was found in a medium-temperature (~250ºC) intracrater active fumarole at La Fossa crater, Vulcano, Aeolian Islands, Sicily, Italy. It occurs on a pyroclastic breccia as colourless to white prismatic crystals up to 0.2 mm long, in association with adranosite, mascagnite, alunite and salammoniac. The mineral is identical to the synthetic compound (NH4)3Al(SO4)3. It is trigonal, space group: R3̅ (no. 148) with a = 15.0324(8), c = 8.8776(5) Å, V = 1737.3(2) Å3 and Z = 6. The six strongest reflections in the X-ray powder diffraction pattern are: [dobs in Å(I)(hkl)] 3.336(100)(131), 7.469(62)(1 1 0), 3.288(60)(122), 4.289(45)(2.31), 2.824(29)(3. 51) , 4.187(27)(012) . The empirical formula based on 12 anions is [(NH4)2.89K0.10] ∑2.99(Al1.18Fe0.01) ∑1.19S2.91O12, and the simplified formula (NH4,K)3Al(SO4)3. The measured density is 2.12(1) g/cm3, calculated density 2.143 g/cm3. The mineral is uniaxial(-) with ω = 1.545(3) and Ɛ = 1.532(3) (λ = 589 nm). Using single-crystal diffraction data, the structure was refined to a final R(F) = 0.0258 for 998 independent observed reflections [I > 2σ(I)]. In spite of having unit-cell parameters comparable with those of pyracmonite, the two minerals are not isostructural; the difference is related to a disordered conformation of the sulfate anions about the two independent Al3+ ions in aluminopyracmonite.

D’ansite-(Mn), IMA 2011-064. CNMNC Newsletter No. 11, December 2011

P. A. WILLIAMS (Chairman, CNMNC), F. HATERT (Vice-Chairman, CNMNC), M. PASERO (Vice-Chairman, CNMNC) AND S. J. MILLS (Secretary, CNMNC) 1 School of Natural Sciences, University of Western Sydney, Locked Bag 1797, Penrith, NSW 2751, Australia p.williams@uws.edu.au 2 Laboratoire de Minéralogie, Université de Liège, B-4000 Liège, Belgium fhatert@ulg.ac.be 3 Dipartimento di Scienze della Terra, Università degli Studi di Pisa, Via Santa Maria 53, I-56126 Pisa, Italy pasero@dst.unipi.it 4 Geosciences, Museum Victoria, GPO Box 666, Melbourne 3001, Victoria, Australia smills@museum.vic.gov.au

Scandium minerals in the miaroles of granite at Baveno, Italy

The discovery of bazzite [Be 3 Sc 2 Si 6 O 18 ] in the granites at Baveno, Italy, dates back to 1915, just a few years after the discovery in Norway of thortveitite, the first known scandium mineral (1911). In 1982 two new scandium minerals, cascandite [CaScSi 3 O 8 (OH)] and jervisite [NaScSi 2 O 6 ] were discovered as additional rarities at Baveno. Owing to the increased activity of collectors, a number of additional finds of bazzite have resulted; similarly, other scandium minerals were recognized to be present, among which thortveitite (Orlandi, 1990) and scandiobabingtonite [Ca 2 FeScSi 5 O 14 (OH)] (Orlandi et al ., 1998), the former sometimes affording interesting blue, Mn-bearing specimens (Gramaccioli et al ., 2000b). On considering all these discoveries, five of the nine scandium minerals known so far occur at Baveno, which is the type locality for four of them. However, scandium phosphates such as kolbeckite [ScPO 4 ·2H 2 O] and pretulite [ScPO 4 ] which are relatively diffuse in nature are absent. A possible reason for such a situation is linked to the particular process of formation of these minerals at Baveno, which most probably involves disruption of REE/Sc fluoride complexes following the deposition of relatively abundant fluorite and zinnwaldite from the solutions; there is marked similarity with the Norwegian locality of Heftetjaern, Tordal, where fluorite is common and many of the Sc-bearing species are the same as at Baveno.

Argesite, (NH4)7Bi3Cl16, a new mineral from La Fossa Crater, Vulcano, Aeolian Islands, Italy: A first example of the [Bi2Cl10]4− anion

Abstract The new mineral argesite, ammonium bismuth chloride (NH4)7Bi3Cl16, was found in a mediumtemperature (~250 °C) active fumarole at La Fossa crater, Vulcano, Aeolian Islands, Sicily, Italy. The mineral occurs on a pyroclastic breccia as pale-yellow crystals up to 0.15 mm in length, in association with bismuthinite, adranosite, brontesite, demicheleite-(Br), demicheleite-(Cl), and panichiite. Argesite is trigonal, space group: R3̅c (no. 167) with Z = 18; the unit-cell parameters are (single-crystal data): a = 13.093(1), c = 102.682(1) Å, and V = 15245(2) Å3. The six strongest reflections in the X-ray powder diffraction pattern are: [dobs(Å) (I) (hkl)] 3.164 (100) (0 3 18), 3.808 (44) (2̅ 2 20), 2.742 (78) (2̅ 4 21), 6.14 (16) (1̅ 2 6), 1.906 (16) (0 0 5̅4̅), 1.686 (13) (5̅ 6 34). The mineral is uniaxial (-), with ω = 1.731(2), ε = 1.725(2) (589 nm). The IR spectrum shows absorptions at 3188(vs), 3060(s), and 1397(vs) cm-1, in agreement with the presence of the ammonium ion. Chemical analyses obtained by EDS electron microprobe gave (average wt%) Bi 42.26, Cl 32.57, Br 13.06, I 0.95, K 2.46, Tl 0.88, NH4 7.82 (by difference) total 100.00, corresponding to the empirical formula: [(NH4)6.29K0.91Tl0.06]Σ7.26Bi2.93(Cl13.33Br2.37I0.11)Σ15.81. The measured density is 2.88(1) g/cm3. The structure was refined, using single-crystal diffraction data, to a final R = 0.0345 for 1289 independent observed reflections [I > 2σ(I)]. It contains Bi2Cl4-10 and BiCl3-6 anions where the Bi atoms are octahedrally coordinated, and NH+4 cations are partially replaced by K+ and Tl+ ions.