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)Σ1.00. 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.

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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.

Demartinite, ideally K 2 SiF 6 , is a new hexagonal polymorph of potassium ß uorosilicate, found in a fumarole at the rim of La Fossa crater, Vulcano Island, Aeolian Archipelago, Sicily, Italy. The mineral occurs as colorless hexagonal pyramidal crystals up to 0.3 mm across on a fragment of altered pyroclastic breccia, together with hieratite, avogadrite and knasibÞ te, a recently approved tetraß uoroborate-hexaß uorosilicate of Na and K. The mineral is hexagonal (6mm), space group P6 3 mc, with a 5.6461(8) and c 9.2322(18) Å, V 254.88(7) Å 3. The crystals are sharp hexagonal pyramids {112}, terminated by the {001} pedion. The crystal structure has been reÞ ned to a Þ nal R index of 0.018; its SiF 6 2groups have the same geometry as in the other natural ß uorosilicates known. There are two independent twelve-coordinated K sites, displaying distorted cuboctahedral and hexagonal cuboctahedral coordination, respectively. The K-F distances are in the range 2.800(2)-3.087(2) Å, with an average of 2.885 Å. The Si-F distances in the octahedral SiF 6 2anion range from 1.681(2) to 1.689(2) Å, with an average of 1.685 Å. The chemical analysis obtained by EDS microprobe gave (wt%) K 35.1, Si 12.4, F 51.0, Na 0.2, total 98.7, corresponding to the empirical formula (K 2.00 Na 0.02) ⌺2.02 Si 0.99 F 5.99 , based on nine atoms per formula unit. The calculated density is 2.87 g cm-3 , the measured density obtained by ß otation in heavy liquids is 2.85 g cm-3. The indices of refraction are: 1.350 ± 0.005; 1.340 ± 0.005 (589 nm). Demartinite is uniaxial (-) and nonpleochroic (colorless). The strongest six lines in the X-ray powder-diffraction pattern [d obs in Å(I) hkl] are: 2.301(100)(004), 4.62(75)(002), 2.155(54)(022), 4.32(43)(011), 4.90(25)(010) and 2.358(22)(021). The mineral is named in honor of Prof. Francesco Demartin (b. 1953), who has made signiÞ cant contributions to the chemistry of metallic clusters and to the crystal structure of Alpine rare-earth minerals and uranium minerals. Both the mineral and the mineral name have been approved by the Commission on New Minerals and Mineral Names of the IMA (No. 2006-034).

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