Markwelchite, ideally TlPbSbS3, is a new mineral from the hydrothermal deposit of Jas Roux, Hautes-Alpes, France. It occurs as a black anhedral crystal associated closely with protochabournéite. Microhardness measurements (VHN15) gave a mean value of 197 kg/mm2 corresponding to a Mohs hardness of ~3–4. In plane-polarised incident light, markwelchite is grey in colour. Under crossed polars, it is distinctly anisotropic with greyish white to bluish rotation tints, with bright red internal reflections. Reflectance percentages (Rmin and Rmax) are: 28.5, 31.5 (471.1 nm); 28.3, 30.7 (548.3 nm); 27.9, 30.3 (586.6 nm); and 27.6, 29.8 (652.3 nm). The mean of 5 electron microprobe spot analyses gave Tl 34.67(45), Pb 31.86(25), Sb 15.06(15), As 2.37(5), S 15.35(20), total 99.31 wt.%, corresponding, on the basis of a total of 6 atoms per formula unit and structural results, to Tl1.063Pb0.964(Sb0.775As0.198)Σ0.973S3.000. Single-crystal X-ray diffraction studies revealed that markwelchite is isotypic with richardsollyite, TlPbAsS3. It is monoclinic, space group P21/c, with the following unit-cell parameters: a = 8.9144(3), b = 8.4513(3), c = 8.6511(3) Å, β = 108.723(4)°, V = 617.27(4) Å3 and Z = 4. The five strongest observed powder-diffraction lines [d in Å (Irel)(hkl)] are: 3.88 (100)($\bar{2}$11); 3.78 (90)(210); 3.29 (90)(102); 2.73 (85)($\bar{1}$13); and 2.93 (75)(022). The crystal structure can be described as formed by (100) [Me2(SbS3)]– layers sandwiching the Me1+ cations. The Me1 site has a seven-fold coordination, whereas the Me2 site has an 6+2 coordination corresponding to a distorted, bicapped trigonal prismatic coordination, and the Sb site displays a trigonal pyramidal coordination with three S atoms and Sb at the apex.

The name markwelchite honours Dr Mark D. Welch of the Natural History Museum, London, UK.

The new mineral has been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA2024–001). A discussion on the relationships between markwelchite and synthetic TlPbSbS3 is also provided.

Thunderbayite (IMA2020–042), ideally TlAg3Au3Sb7S6, is a new mineral from the Hemlo gold deposit, Marathon, Ontario, Canada. It occurs as very rare anhedral rims up to 70 μm across in contact with aurostibite and associated spatially with stibarsen, biagioniite and native gold in a calcite matrix. Thunderbayite is opaque with a metallic lustre and shows a black streak. In reflected light, thunderbayite is weakly bireflectant and faintly pleochroic from grey–blue to slightly greenish grey–blue. Under crossed polars, it is weakly anisotropic with bluish to light-blue rotation tints. Internal reflections are absent. Reflectance percentages for the four Commission on Ore Mineralogy wavelengths (Rmin, Rmax) are: 37.9, 38.4 (471.1 nm); 35.3, 36.0 (548.3 nm); 33.9, 34.4 (586.6 nm); and 32.0, 32.5 (652.3 nm), respectively. A mean of five electron-microprobe analyses gave Ag 14.91(16), Au 27.40(22), Tl 9.37(9), Sb 39.80(34) and S 8.61(7), for a total of 100.09 wt.%, corresponding, on the basis of a total of 20 atoms, to Tl1.00Ag3.01Au3.03Sb7.12S5.84. Thunderbayite is triclinic, space group P1, with a = 8.0882(5), b = 7.8492(5), c = 20.078(1) Å, α = 92.518(5), β = 93.739(5), γ = 90.028(6)°, V = 1270.73(9) Å3 and Z = 2. The five strongest powder-diffraction lines [d in Å (I/I0) (hkl)] are: 4.04 (100) (200); 3.92 (80) (020); 2.815 (50) (220/$\bar{2}$20); 2.566 (45) ($\bar{1}$17); and 2.727 (40) (0$\bar{1}$7). The crystal structure [R1 = 0.0220 for 5521 reflections with I > 2σ(I)] can be considered as a strongly deformed pyrite-type structure with several metal–metal bonds. Thunderbayite shows close similarities with criddleite, TlAg2Au3Sb10S10, from an optical, chemical and structural point of view. The new mineral is named for the Thunder Bay district, Ontario, in which the Hemlo gold deposit is located.

Biagioniite, ideally Tl2SbS2, is a new mineral from the Hemlo gold deposit, Marathon, Ontario, Canada. It occurs as very rare anhedral crystals up to 65 μm across associated with aurostibite, stibarsen and native gold in a calcite matrix. Biagioniite is opaque with a metallic lustre and shows a black streak. In reflected light biagioniite is moderately bireflectant and not pleochroic. Under crossed polars it is weakly anisotropic with blueish to light-blue rotation tints. Internal reflections are absent.

Reflectance percentages for the four standard wavelengths (Rmin and Rmax) are 35.9 and 37.5 (471.1 nm); 34.7 and 36.2 (548.3 nm); 33.8 and 35.3 (586.6 nm); and 31.5 and 33.7 (652.3 nm), respectively. A mean of four electron microprobe analyses gave: Tl 65.12(31), Ag 3.52(9), Sb 20.22(12), S 10.80(8), total 99.66 wt.%, corresponding, on the basis of a total of 5 atoms, to (Tl1.87Ag0.19)Σ2.06Sb0.97S1.97. Biagioniite is monoclinic, space group Pc, with a = 11.0895(9), b = 14.3124(11), c = 7.9352(6) Å, β = 96.230(8)°, V = 1252.02(17) Å3 and Z = 8. The four strongest powder-diffraction lines [d in Å (I/I0) (hkl)] are: 3.56 (100) (310); 3.37 (75) ($\bar{2}$31); 3.79 (60) (012); 3.03 (60) (032). In the crystal structure [R1 = 0.024 for 2655 reflections with I > 2σ(I)], thallium adopts various coordinations extending from quasi-linear to quasi-tetrahedral. Antimony forms Sb–Sb pairs, which lead to the formula [Tl+1]4[Sb2]4+[S2–]4. Biagioniite is isostructural with dervillite, Ag2AsS2. The new mineral has been approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (IMA2019–120) and named for Cristian Biagioni, Associate Professor of Mineralogy at the Department of Earth Sciences of the University of Pisa, Italy.

Markhininite, ideally TlBi(SO4)2, was found in a fumarole of the 1st cinder cone of the North Breach of the Great Fissure Tolbachik volcano eruption (1975–1976), Kamchatka Peninsula, Russia. Markhininite occurs as white pseudohexagonal plates associated with shcherbinaite, pauflerite, bobjonesite, karpovite, evdokimovite and microcrystalline Mg, Al, Fe and Na sulfates. Markhininite is triclinic, P, a = 7.378(3), b = 10.657(3), c = 10.657(3) Å , α = 61.31(3), β = 70.964(7), γ = 70.964(7)º, V = 680.2(4) Å3, Z = 4 (from single-crystal diffraction data). The eight strongest lines of the X-ray powder diffraction pattern are (I/d/hkl): 68/4.264/111, 100/3.441/113, 35/3.350/222, 24/3.125/122, 23/3.054/202, 45/2.717/022, 20/2.217/331, 34/2.114/204. Chemical composition determined by electron microprobe analysis is (wt.%): Tl2O 35.41, Bi2O3 38.91, SO3 25.19, total 99.51. The empirical formula based on 8 O a.p.f.u. is Tl1.04Bi1.05S1.97O8. The simplified formula is TlBi(SO4)2, which requires Tl2O 35.08, Bi2O3 38.48, SO3 26.44, total 100.00 wt.%. The crystal structure was solved by direct methods and refined to R1 = 0.055 on the basis of 1425 independent observed reflections. The structure contains four Tl+ and two Bi3+ sites in holodirected symmetrical coordination. BiO8 tetragonal antiprisms and SO4 tetrahedra in markhininite share common O atoms to produce [Bi(SO4)2]– layers of the yavapaiite type. The layers are parallel to (111) and linked together through interlayer Tl+ cations. The mineral is named in honour of Professor Yevgeniy Konstantinovich Markhinin (b. 1926), Institute of Volcanology, Russian Academy of Sciences, Kamchatka peninsula, Russia, in recognition of his contributions to volcanology. Markhininite is the first oxysalt compound that contains both Tl and Bi in an ordered crystal structure.

Thallium leucite, TlAlSi2O6, has been synthesized at 450°C for 7 days, under ambient conditions, by the transformation of dehydrated analcime NaAlSi2O6 in the presence of excess TlCl. This substitution of Tl for Na leads to confirmation of a thallium-leucite pseudomorph after analcime. Their optical properties, X-ray powder diffraction patterns, electron microprobe analysis, infrared spectra, and X-ray photoelectron spectroscopy have characterized the synthetic Tl-leucites. The IR spectra show that the mid-IR modes T-O stretching and T-O-T bending vibrations for TlAlSi2O6 are more resemblant of those for analcime than for leucite, KAlSi2O6. This resemblance implies that Tl cation enters the W-site rather than the S-site in the analcime structure: Na (S) + H2O (W) ⇋ □ + K (leucite) ⇋ □ + Tl (Tl- leucite), where □ represents an S-site vacancy. The mechanism of this substitution is supported by the crystal chemical constraints: inasmuch as the S-site is smaller than the W-site, Tl+ cations being larger than Na+ plainly prefer the latter site to the former. One inference from the binding energy for Tl+ by XPS is that Tl+ occupies the extra-framework site in synthetic leucite pseudomorph, rather than the smaller tetrahedral site. The difference in Al/Si disordering between analcime and leucite and the nonstoichiometry due to the solid solution of the □Si3O6 component into the leucite structure may provide a fundamental insight into understanding why TlAlSi2O6 deviates from the trend defined by K-, Rb- and CsAlSi2O6 leucite series on the a-c parameter diagram, inasmuch as these three cations in the leucite structure occupy the W-sites. Finally, synthesis of TlAlSi2O6 leucite has an implication for the existence of other polymorphs due to different degrees of Al/Si disordering, except for high- and low-temperature leucites already known: natural leucites crystallized directly through igneous processes are different from those formed by substitution of K for Na in analcimes.

Karpovite, ideally Tl2VO(SO4)2(H2O), was found in a fumarole of the 1st cinder cone of the North Breach of the Great Fissure Tolbachik volcano eruption (1975–1976), Kamchatka Peninsula, Russia. Karpovite occurs as bundles of white, needle-like crystals associated with shcherbinaite, pauflerite, bobjonesite, markhininite, evdokimovite and microcrystalline Mg, Al, Fe and Na sulfates. Karpovite is monoclinic, P21, a = 4.6524(4), b = 11.0757(9), c = 9.3876(7) Å , β = 98.353(2)º, V = 478.60(7) Å3, Z = 2 (from single-crystal diffraction data). The eight strongest lines of the X-ray powder diffraction pattern are (I/d/hkl): 64/4.289/012, 81/4.253/110, 38/3.683/111, 47/3.557/022, 100/3.438/21, 52/2.982/013, 59/2.945/112, 54/2.354/132. The chemical composition determined by the electron microprobe analysis is (wt.%) Tl2O 61.43, VO2 11.53, SO3 23.55, H2O 2.61, total 99.12. The empirical formula (calculated on the basis of 10 O a.p.f.u.) is Tl2.00V0.96S2.03O9(H2O). The simplified formula of karpovite is Tl2VO(SO4)2(H2O), which requires Tl2O 61.93, VO2 12.09, SO3 23.34, H2O 2.62 total 100.00 wt.%. The crystal structure was solved by direct methods and refined to R1 = 0.026 for 4196 independent observed reflections. The structure contains two symmetrically independent Tl+ sites, one V4+ site and two S6+ sites. VO5H2O octahedra and SO4 tetrahedra link together by sharing corners to form kröhnkite-type stripes parallel to the a axis with their planes oriented parallel to (021) and (02). Tl+ cations are located between the chains, linked into a three-dimensional structure. The new mineral is named in honour of Professor Gennadii Alexandrovich Karpov (b. 1938), volcanologist at the Institute of Volcanology, Russian Academy of Sciences, Petropavlovsk-Kamchatskii, Kamchatka Peninsula, Russia.

Evdokimovite, ideally Tl4(VO)3(SO4)5(H2O)5, was found in a fumarole of the 1st cinder cone of the North Breach of the Great Fissure Tolbachik volcano eruption of 1975–1976, Kamchatka Peninsula, Russia. Evdokimovite occurs as thin, colourless needles up to 0.09 mm long associated with shcherbinaite, pauflerite, bobjonesite, markhininite, karpovite and microcrystalline Mg, Al, Fe and Na sulfates. Evdokimovite is monoclinic, P21/n, a = 6.2958(14), b = 10.110(2), c = 39.426(11) Å , β = 90.347(6)º, V = 2509.4(10) Å3 and Z = 4 (from single-crystal diffraction data). The eight strongest lines of the powder X-ray diffraction pattern are (I/d/hkl): 57/9.793/011, 100/8.014/013, 26/6.580/006, 19/ 4.011/026, 29/3.621/118, 44/3.522/125, 19/3.010/036, 21/2.974/212. Chemical composition determined by the electron microprobe analysis is (wt.%): Tl2O 55.40, VO2 14.92, SO3 25.83, H2O 5.75, total 101.90. The empirical formula for evdokimovite calculated on the basis of (Tl + V + S) = 12 a.p.f.u. is Tl4.10V2.83S5.07H10.00O27.94. The simplified formula is Tl4(VO)3(SO4)5(H2O)5. The crystal structure was solved by direct methods and refined to R1 = 0.11 on the basis of 3660 independent observed reflections. V4+O6 octahedra and SO4 tetrahedra share common corners to form two types of vanadyl-sulfate chains, [(VO)(H2O)2(SO4)2]2– and [(VO)2(H2O)3(SO4)3]2–. Thallium atoms are located in between the chains. The structure can be described as a stacking of layers of two types, A and B. The A layer contains [(VO)2(H2O)3(SO4)3]2– chains and the Tl2 and Tl3 atoms, whereas the B layer contains [(VO)(H2O)2(SO4)2]2– chains and the Tl1 atoms. Stacking of the layers can be described as ...A’*BAA’B*A*..., where A and A’ denote A layers with opposite orientations of the [(VO)2(H2O)3(SO4)3]2– chains, and the A* and B* layers are rotated by 180º relative to the A and B layers, respectively. [(VO)2(H2O)3(SO4)3]2– chains are modulated and are arranged to form elliptical tunnels hosting disordered Tl(4), Tl(4A) and Tl(4B) sites. The new mineral is named in honour of Professor Mikhail Dmitrievich Evdokimov (1940–2010), formerly of the Department of Mineralogy, St Petersburg State University, for his contributions to mineralogy and petrology, and especially for teaching mineralogy to several generations of students at the University. Evdokimovite is the most complex V4+ sulfate known to date with structural information amounting to 1130 bits per unit cell, which places evdokimovite among minerals with the complexity of the vesuvianite group.

The crystal structure of the rare mineral dalnegroite, Tl5−xPb2x(As,Sb)21−xS34 with x ≈ 1, was determined for a crystal from Lengenbach, Binn Valley, Switzerland. The structure is triclinic, space group P1, with a = 16.218(3), b = 42.546(7), c = 8.558(1) Å , α = 95.70(4), β = 90.18(3), γ = 96.38(4)°, V = 5838.9(9) Å3, Z = 4. Refinement of an isotropic model led to an R1 index of 0.0536 for 22226 observed reflections and 980 parameters, and R1 = 0.0590 for all 25266 independent reflections. Although dalnegroite cannot be considered a layered compound, its structure can be usefully described as a regular alternation of two kinds of layers stacked along the b axis, with four layers in the unit cell: (1) a layer 7.8 Å thick, at y ≈ 0.15 and 0.65, can be considered as derived from the SnS archetype; (2) a layer 13.6 Å thick, at y ≈ 0.35 and 0.85, derived from the PbS archetype. Different chemical compositions, such as Tl:Pb and Sb:As ratios, for different samples belonging to the chabournéite-dalnegroite family could play a central role in controlling different degrees of order, leading to different superstructures.

A third world occurrence of rouxelite, ideally Cu2HgPb22Sb28S64(O,S)2, has been identified from the baryte-pyrite-Fe oxides ore of Monte Arsiccio mine, near Sant’Anna di Stazzema (Apuan Alps, Tuscany, Italy). Rouxelite occurs as mm-sized acicular crystals, black in colour, with bluish-violet iridescence, in vugs of carbonate + baryte + quartz veins embedded in dolostones from the Sant’Olga tunnel. It is associated with Tl-bearing chovanite, sphalerite and valentinite. Its X-ray powder diffraction pattern gives unit-cell parameters a = 43.10(2), b = 4.060(2), c = 37.88(2) Å, β = 117.33(2)°, V = 5889(5) Å3. Electron-microprobe data reveal a complex chemistry, with additional minor elements (wt.%): Tl (0.6–1.7), Ag (0.4–0.6), As (0.2–0.6) and Bi (≤0.05). This indicates a widespread substitution of Hg by Ag, according to Hg + Pb = Ag + Sb and incorporation of Tl, with some Ag, according to 2Pb = Sb + (Tl, Ag). The occurrence of mixed (Hg, Ag) and (Hg, Cu) sites in natural sulfides and sulfosalts is briefly reviewed. The Tl-content of the samples studied is a characteristic fingerprint agreeing with the Tl-rich nature of the mineral assemblage from Monte Arsiccio. Rouxelite therefore constitutes a new example of a Tl-bearing sulfosalt.

Dalnegroite, ideally Tl4Pb2(As12Sb8)Σ20S34, is a new mineral from Lengenbach, Binntal, Switzerland. It occurs as anhedral to subhedral grains up to 200 μm across, closely associated with realgar, pyrite, Sb-rich seligmanite in a gangue of dolomite. Dalnegroite is opaque with a submetallic lustre and shows a brownish-red streak. It is brittle; the Vickers hardness (VHN25) is 87 kg mm-2 (range: 69—101) (Mohs hardness ∼3—3½). In reflected light, dalnegroite is highly bireflectant and weakly pleochroic, from white to a slightly greenish-grey. In cross-polarized light, it is highly anisotropic with bluish to green rotation tints and red internal reflections.

According to chemical and X-ray diffraction data, dalnegroite appears to be isotypic with chabournéite, Tl5-xPb2x(Sb,As)21-xS34. It is triclinic, probable space group P1, with a = 16.217(7) Å, b = 42.544(9) Å, c = 8.557(4) Å, α = 95.72(4)°, β = 90.25(4)°, γ = 96.78(4)°, V = 5832(4) Å3, Z = 4.

The nine strongest powder-diffraction lines [d(Å) (I/I0) (hkl)] are: 3.927 (100) ( 10 0); 3.775 (45) (22); 3.685 (45) (60); 3.620 (50) (440); 3.124 (50) (2); 2.929 (60) (42); 2.850 (70) (42); 2.579 (45) (0 2); 2.097 (60) (024). The mean of 11 electron microprobe analyses gave elemental concentrations as follows: Pb 10.09(1) wt.%, Tl 20.36(1), Sb 23.95(1), As 21.33(8), S 26.16(8), totalling 101.95 wt.%, corresponding to Tl4.15Pb2.03(As11.86Sb8.20)S34. The new mineral is named for Alberto Dal Negro, Professor in Mineralogy and Crystallography at the University of Padova since 1976.

The new mineral species arsiccioite, AgHg2TlAs2S6, was discovered in the baryte-pyrite-iron oxide ore deposit exploited at the Monte Arsiccio mine, near Sant’Anna di Stazzema (Apuan Alps, Tuscany, Italy). It occurs as anhedral grains scattered in microcrystalline baryte, associated with cinnabar, laffittite, protochabournéite, pyrite, realgar, Hg-bearing sphalerite and stibnite. Arsiccioite is red, with a metallic to sub-metallic lustre. Minimum and maximum reflectance data for COM wavelengths in air are [λ (nm): R (%)]: 471.1: 29.0/29.4; 548.3: 27.6/28.3; 586.6: 26.1/26.5; 652.3: 24.2/24.6. Electron microprobe analyses give (wt.%): Cu 0.78(6), Ag 8.68(21), Zn 0.47(27), Fe 0.04(1), Hg 35.36(87), Cd 0.20(5), Tl 18.79(33), As 10.77(19), Sb 4.75(10), S 18.08(21), Se 0.07(5), total 97.99(44). On the basis of ΣMe = 6 a.p.f.u., the chemical formula is Ag0.87(2)Cu0.13(1)Zn0.08(4)Fe0.01(1)Hg1.91(5)Cd0.02(1)Tl1.00(2) (As1.56(2)Sb0.42(1))S1.98S6.12(6)Se0.01(1). Arsiccioite is tetragonal, I2m, with a 10.1386(6), c 11.3441(5) Å, V 1166.1(2) Å3, Z = 4. The main diffraction lines of the powder diagram are [d(in Å), visually estimated intensity, hkl]: 4.195, m, 211; 3.542, m, 103; 3.025, vs, 222; 2.636, m, 114; 2.518, s, 400 and 303. The crystal structure of arsiccioite has been refined by single-crystal X-ray data to a final R1 = 0.030, on the basis of 893 observed reflections. It shows a three dimensional framework of (Hg,Ag)- centred tetrahedra (1 M1 + 2 M2), with channels parallel to [001] hosting TlS6 and (As,Sb)S3 disymmetric polyhedra. Arsiccioite is derived from its isotype routhierite M1CuM2Hg2TlAs2S6 through the double heterovalent substitution M1Cu+ + M2Hg2+ → M1Hg2+ + M2Ag+. This substitution obeys a steric constraint, with Ag+, the largest cation relative to Hg2+ and Cu+, entering the largest M2 site. The ideal crystal chemical formula of arsiccioite is M1HgM2(Hg0.5Ag0.5)2TlAs2S6. The crystal chemistry of the routhierite isotypic series is discussed. Finally, the distribution of Hg ore minerals in the Apuan Alps is reviewed.

Boscardinite, ideally TlPb4(Sb7As2)∑9S18, has been described recently as a new homeotypic derivative of baumhauerite, found at Monte Arsiccio mine, Apuan Alps, Tuscany, Italy. New findings of boscardinite in different mineral associations of this deposit have allowed the collection of new crystal-chemical data. Electron-microprobe analysis of the crystal used for the single-crystal X-ray diffraction study gave (in wt.%): Ag 1.81(5), Tl 12.60(21), Pb 17.99(12), Hg 0.14(5), As 9.36(12), Sb 33.60(27), S 23.41(30),Cl 0.06(1), total 98.97(100). On the basis of ∑Me = 14 apfu, it corresponds to Ag0.42Tl1.52Pb2.14Hg0.02 (Sb6.82As3.08)∑9.90S18.04Cl0.04. With respect to the type specimen, these new findings are characterized by a strong Pb depletion, coupled with higher Tl contents, and a significant As enrichment. The single-crystal X-ray diffraction study of this (Tl,As)-enriched boscardinite confirms the structural features described for the type sample. The unit-cell parameters are a = 8.1017(4), b = 8.6597(4), c = 22.5574(10) Å, α = 90.666(2), β = 97.242(2), γ = 90.850(2)°, V = 1569.63(12) Å3, space group P̄1. The crystal structure was refined down to R1 = 0.0285 on the basis of 6582 reflections with Fo > 4σ(Fo). Arsenic is dominant in three MeS3 sites, compared to one in type boscardinite. The main As-enrichment is observed in the sartorite-type sub-layer. Owing to this chemical peculiarity, (Tl, As)-rich boscardinite shows alternation, along b, of Sb-rich sites and As-rich sites; this feature represents the main factor controlling the 8 Å superstructure. The chemical variability of boscardinite is discussed; the Ag increase observed here gets closer to stoichiometric AgTl3Pb4(Sb14As6)∑20S36 (Z = 1), against possible extension up to AgTl2Pb6(Sb15As4)∑19S36 for type boscardinite.

The new mineral species ralphcannonite, AgZn2TlAs2S6, was discovered in the Lengenbach quarry, Binn Valley, Wallis, Switzerland. It occurs as metallic black equant, isometric to prismatic crystals, up to 50 μm, associated with dufrénoysite, hatchite, realgar and baryte. Minimum and maximum reflectance data for COM wavelengths in air are [λ (nm): R (%)]: 471.1: 25.8/27.1; 548.3: 25.2/26.6; 586.6: 24.6/25.8; 652.3: 23.9/24.8. Electron microprobe analyses give (wt.%): Cu 2.01(6), Ag 8.50(16), Zn 10.94(20), Fe 3.25(8), Hg 7.92(12), Tl 24.58(26), As 18.36(19), Sb 0.17(4), S 24.03(21), total 99.76(71). On the basis of 12 atoms per formula unit, the chemical formula of ralphcannonite is Ag0.63(2)Cu0.25(2)Zn1.35(5)Fe0.47(1)Hg0.32(2)Tl0.97(3)[As1.97(6)Sb0.01(1)]Σ1.98(5)S6.03(8). The new mineral is tetragonal, space group I42m, with a = 9.861 (2), c = 11.125(3) Å, V = 1081.8(4) Å3, Z = 4. The main diffraction lines of the calculated powder diagram are [d (in Å), intensity, hkl]: 4.100, 85, 211; 3.471, 40, 103; 2.954, 100, 222; 2.465, 24, 400; 2.460, 39, 303. The crystal structure of ralphcannonite has been refined by X-ray single-crystal data to a final R1 = 0.030, on the basis of 140 observed reflections [Fo > 4σ(Fo)]. It shows a three dimensional framework of (Ag,Zn)-centred tetrahedra (1 M1 + 2 M2), with channels parallel to [001] hosting TlS6 and (As,Sb)S3 disymmetric polyhedra. Ralphcannonite is derived from its isotype routhierite M1CuM2Hg2TlAs2S6 through the double heterovalent substitution M1Cu+ + M2Hg2+ → M1Zn2+ + M2Ag+. This substitution obeys a steric constraint, with Ag+, the largest cation relative to Zn2+ and Cu+, entering the largest M2 site, as observed in arsiccioite. The ideal crystal-chemical formula of ralphcannonite is M1ZnM2(Zn0.5Ag0.5)2TlAs2S6.

Two new occurrences of the lead oxy-sulfosalt chovanite have been identified at the Monte Arsiccio and Pollone mines, Apuan Alps, Tuscany, Italy. Chovanite from Monte Arsiccio occurs as black acicular crystals, up to 5 mm long, associated with rouxelite, robinsonite, sphalerite, valentinite,baryte, dolomite, quartz and Ba-rich K-feldspar ('hyalophane') in metadolostone vugs. Its unit-cell parameters are a = 48.38(5), b = 4.11(4), c = 34.18(4) Å, β = 106.26(2)°, V = 6521(64) Å3, space group C2/m. Very weakreflections indicate the doubling of the b parameter. Electron-microprobe data gave (wt.%): Ag 0.28, Tl 1.51, Pb 45.57, Sb 31.00, As 1.09, S 19.73, Se 0.05, Cl 0.02, sum 99.25. On the basis of ∑Me = 58 apfu, its formula is Ag0.30Tl0.86Pb25.56Sb29.59As1.69S71.52Se0.07Cl0.05.Adding one oxygen atom, it is close to the formula TlPb26(Sb,As)31S72O. Chovanite from Pollone occurs as thick black acicular crystals, up to 1 cm long, associated with baryte and quartz. The high-diffraction quality of the available material allowed the solutionand refinement of the 8 Å crystal structure in the space group P21/c, with unit-cell parameters a = 34.052(3), b = 8.2027(7), c = 48.078(4) Å, β = 106.258(4)°, V = 12891.9(19) Å3. The refinement convergedto R1 = 9.14% on the basis of 19,853 observed reflections with Fo > 4σ(Fo). Electron-microprobe data gave (wt.%): Ag 0.12, Tl 0.54, Pb 48.34, Bi 0.20, Sb 26.71, As 3.37, S 20.23, Cl 0.07, sum 99.57. It corresponds to the formulaAg0.13Tl0.30Pb26.94Bi0.10Sb25.33As5.20S72.85Cl0.20, close to the idealized formula Pb28(Sb,As)30S72O, with a single oxygen atom bound to two (Sb/As) atoms alternating witha vacancy along b as in scainiite and in other Pb oxy-sulfosalts. The crystal chemistry of this 8 Å crystal structure is detailed, taking into account its modular description, the (Sb,As)mSn polymerization, its topological derivation from pellouxite,and the oxygen non-stoichiometry.

The new mineral species ferrostalderite, CuFe2TlAs2S6, was discovered in the Lengenbach quarry, Binn Valley, Wallis, Switzerland. It occurs as minute, metallic, black, equant to prismatic crystals, up to 50 mu;m, associated with dolomite, realgar, baumhauerite (?) and pyrite. Minimum and maximum reflectance data for COM wavelengths in air are [λ (nm): R (%)]: 471.1: 24.2/25.4; 548.3: 23.7/24.7; 586.6: 22.9/23.8; 652.3: 21.0/22.0. Electron microprobe analyses give (wt.%): Cu 6.24(25), Ag 4.18(9), Fe 9.95(83), Zn 4.46(91), Hg 1.22(26), Tl 26.86(62), As 19.05(18), Sb 0.63(6),S 25.39(47), total 97.98(72). On the basis of 12 atoms per formula unit, the chemical formula of ferrostalderite is Cu0.75(2)Ag0.30(1)Fe1.36(10) Zn0.52(11) Hg0.05(1) Tl1.00(1)[As1.94(4)Sb0.04(1)]∑1.98(4)S6.04(4). The new mineral is tetragonal, space group I4̄2 m, with a = 9.8786(5), c = 10.8489(8) Å, V = 1058.71(11) Å3, Z = 4. The main diffraction lines of the calculated powder diagram are [d (in Å), intensity, hkl]: 4.092, 70, 211; 3.493, 23, 220; 3.396, 35, 103; 3.124, 17, 310; 2.937, 100, 222; 2.656, 19, 321; 2.470, 19, 400; 2.435, 33, 303. The crystal structure of ferrostalderite has been refined by Xray single-crystal data to a final R1 = 0.050, on the basis of 1169 reflections with F0 > 4σ(F0). It shows a three dimensional framework of (Cu,Fe)-centred tetrahedra (1M1 + 2 M2), with channels parallel to [001] hosting disymmetric TlS6 and (As,Sb)S3 polyhedra. Ferrostalderite is derived from its isotype stalderite M1CuM2Zn2TlAs2S6 through the homovalent substitution M2Zn2+ → M2Fe2+. The ideal crystal-chemical formula of ferrostalderite is M1CuM2Fe2TlAs2S6.