Adamantine Luster Research Articles

New Minerals from the Redmond Mine, North Carolina, USA: V. Finescreekite and Hayelasdiite, Two New Thiosulfate Minerals Containing Cubane-Like Pb4O4 Structural Units

Abstract The new minerals finescreekite, [Pb4(OH)4](S2O3)2 (IMA2022–030), and hayelasdiite, [Pb4O1.5(OH)2.5]2[Cu+5(S2O3)4(S2O2OH)2(H2O)]·4H2O (IMA2022–021), were found in the Redmond mine, Haywood County, North Carolina, USA, where they occur in a highly unusual secondary assemblage that comprises a variety of rare Pb-Zn-Cu sulfates, thiosulfates, and carbonates. Finescreekite was found in close association with anglesite, cubothioplumbite, redmondite, and steverustite. Hayelasdiite was found in close association with anglesite and steverustite. Finescreekite properties: colorless tablets to about 1.5 mm across; white streak; resinous to adamantine luster; brittle; Mohs hardness ∼ 2½; curved, stepped fracture; excellent cleavage on {001}, fair on {100}, {010}, and {110}; 5.675 g/cm3 calculated density; biaxial (−) with α = 2.00(1), β = 2.04(calc), γ = 2.065(calc), 2V = 75.9(5)°. Hayelasdiite properties: colorless prisms and blades to about 0.5 mm in length; white streak; vitreous to subadamantine luster; brittle; Mohs hardness ∼ 2½; curved fracture; perfect cleavage on {010}; 4.909 g/cm3 calculated density; biaxial (−) with α = 1.89(1), β = 1.95(calc), γ = 1.97(calc), 2V = 58(5)°. Electron probe microanalyses provided the empirical formulae [Pb4(OH)4](S2O3)1.76(SO4)0.24 and [Pb4.00O1.5(OH)2.5]2[Cu+5.00(S2O3)3.24(SO4)0.76(S2O2OH)2(H2O)]·4H2O for finescreekite and hayelasdiite, respectively. Finescreekite is Orthorhombic, P212121, a = 8.2330(9), b = 10.7128(13), c = 14.8256(13) Å, V = 1307.6(2) Å3, and Z = 4. Hayelasdiite is triclinic, P1̄, a = 7.52089(15), b =14.9345(3), c = 17.9895(13) Å, α = 106.727(8), β = 90.966(6), γ = 90.031(6)°, V = 1934.79(16) Å3, and Z = 2. The structures of finescreekite (R1 = 0.061 for 1440 I > 2σI) and hayelasdiite (R1 = 0.055 for 5636 I > 2σI) both contain cubane-like Pb4O4 clusters, [Pb4(OH)4]4+ in finescreekite and [Pb4O1.5(OH)2.5]2.5+ in hayelasdiite. The structure of hayelasdiite also contains a decorated double chain with the formula [Cu+5(S2O3)4(S2O2OH)2(H2O)]5−.

New Minerals from the Redmond Mine, North Carolina, USA: VI. Boojumite and Kennygayite, Two New Minerals with Structures Based on Chains of Oxocentered OPb4 Tetrahedra

Abstract The new minerals boojumite, Pb8O4(OH)2(S2O3)3 (IMA2022-028), and kennygayite, [Pb4O2(OH)2](SO4) (IMA2022-032), were found in the Redmond mine, Haywood County, North Carolina, USA, where they occur in a highly unusual secondary assemblage that comprises a variety of rare Pb-Zn-Cu sulfates, thiosulfates, and carbonates. Boojumite was found in close association with bechererite, caledonite, cubothioplumbite, hexathioplumbite, hydroredmondite, redmondite, steverustite, and sulfatoredmondite. Kennygayite was found in close association with bechererite, chenite, cherokeeite, redmondite, sidpietersite, and steverustite. Boojumite properties: yellow prisms or blades to about 0.3 mm long; very pale yellow streak; adamantine luster; brittle; Mohs hardness ∼ 2½; irregular fracture; no cleavage; 6.619 g/cm3 calculated density; biaxial (−) with α = 2.0350(calc.), β = 2.0710(calc.), γ = 2.0725(calc.), 2V = 23(3)°. Kennygayite properties: colorless to pale yellow wedges and lozenge-shaped wafers, up to about 1 mm across; white streak; adamantine luster; brittle; Mohs hardness ∼ 2½; irregular, stepped fracture; perfect cleavage on {001}; 7.078 g/cm3 calculated density; biaxial (−) with α = 1.98(calc.), β = 2.01 (est.), γ = 2.09 (calc.), 2V = 58(5)°. Electron probe microanalyses provided the empirical formulae Pb8O4(OH)2(S2O3)2.57(SO4)0.43 and [Pb4O2(OH)2](SO4)0.87(S2O3)0.13 for boojumite and kennygayite, respectively. Boojumite is orthorhombic, Pnma, a = 14.0103(8), b = 20.5529(10), c = 7.2668(5) Å, V = 2092.5(2) Å3, and Z = 4. Kennygayite is triclinic, P, a = 6.3785(5), b = 7.4519(6), c = 10.3112(8) Å, α = 75.234(5), β = 79.388(6), γ = 88.175(6)°, V = 465.76(6) Å3, Z = 2. The structures of boojumite (R1 = 0.057 for 1538 I > 2σI) and kennygayite (R1 = 0.046 for 2419 I > 2σI) are both based on chains of edge-sharing oxocentered OPb4 tetrahedra. The chain in boojumite is sinuous, whereas that in kennygayite is zig-zag.

Désorite, Pb2(Fe3+6Zn)O2(PO4)4(OH)8, a New Phosphate Mineral Isotypic with Jamesite

The new mineral désorite, Pb2(Fe3+6Zn)O2(PO4)4(OH)8, is a secondary oxidation-zone mineral discovered on the dumps of the Schöne Aussicht mine, Dernbach, Westerwaldkreis, Rhineland-Palatinate, Germany. The crystals are irregular blades up to about 0.25 mm long, occurring in subparallel and radial aggregates. Désorite is brownish red. It has an orange streak, adamantine luster, brittle tenacity, splintery and curved fracture and two cleavages: {021¯} perfect and {001} good. It has a hardness (Mohs) of about 3 and is nonfluorescent in both long- and short-wave ultraviolet illumination. The calculated density is 4.633 g/cm3. Optically, crystals are biaxial (+) with α = 2.00(1), β = 2.02(calc) and γ = 2.10(calc) (white light). The 2V is 54(2)° and the optical orientation is Y ~⊥{021¯}, X ∧ a ≈ 13°. The mineral is pleochroic: X yellow brown, Y red brown, Z red brown; X < Y ≈ Z. The empirical formula from electron microprobe analysis is Pb1.93(Zn0.50Fe3+6.29☐0.21)Σ7.00(P3.90As0.10)Σ4.00O26H8.28. Désorite is triclinic, space group P1¯; the unit-cell parameters are a = 5.4389(7), b = 9.3242(13), c = 10.0927(12) Å, α = 109.024(8), β = 90.521(6), γ = 97.588(7)°, V = 478.90(11) Å3 and Z = 1. Désorite has a framework structure (R1 = 0.0487 for 937 I > 2σI reflections) assembled from Fe3+O6 octahedra and PO4 tetrahedra, with Pb occupying cavities in the framework. The Fe3+O6 octahedra in the framework occur in edge-sharing chains, edge-sharing trimers and individual octahedra, all sharing corners with each other and with PO4 tetrahedra. Désorite is isostructural with jamesite and lulzacite.

A New Mineral Hanauerite, AgHgSI, and Common Crystal Chemical Features of Natural Mercury Sulphohalides

A new mineral, hanauerite, ideally AgHgSI, was found in the oxidation zone of Ag- and Hg-bearing ores at two old, abandoned mines in Rhineland-Palatinate, Germany. In a holotype specimen originating from the Schöne Aussicht Mine, Dernbach, Westerwald, it is associated with plumbogummite–hinsdalite series of minerals and goethite. In cotype from the Friedrichssegen Mine, Bad Ems, it is associated with perroudite, goethite, and quartz. At both localities, hanauerite occurs as a prismatic crystal up to 0.15 mm long and up to 0.02 mm thick. The mineral is yellow, transparent, with an adamantine lustre. It is brittle, and cleavage was not observed. The calculated density values are 6.671 and 6.575 g cm−3 for holotype and cotype, respectively. The empirical formulae calculated (from electron microprobe data) based on the sum of all atoms = 4 apfu are Ag0.95Hg1.00S1.01(I0.83Br0.19Cl0.03)Σ1.05 for holotype and Ag0.97Hg0.97S1.05(I0.76Br0.25)Σ1.01 for cotype. Hanauerite is orthorhombic, space group Pmma; the unit cell parameters (from single-crystal X-ray diffraction data; holotype/cotype) are: a = 9.932(2)/9.9256(8), b = 4.6219(19)/4.6209(2), c = 9.891(4)/9.9006(4) Å, V = 454.0(3)/454.19(5) Å3, and Z = 4. The crystal structure was studied on single crystals extracted from both holotype and cotype specimens; R1 = 0.0416 (holotype) and =0.0544 (cotype). In hanauerite, Hg2+ cations centre strongly distorted octahedra with two short Hg–S bonds (Hg and S atoms build “crankshaft-type” chains) and four strongly elongated Hg–I bonds. The Hg-centred octahedra are connected via common edges and faces to form corrugated layers; Ag+ cations are located between these layers. Hanauerite is named in honour of the German mineral collector Dr. Alfred Hanauer (1912–1988). The common crystal chemical features of mercury sulphohalide minerals are discussed.

Napoliite, Pb2OFCl, a new mineral from Vesuvius volcano, and its relationship with dimorphous rumseyite

AbstractNapoliite, ideally Pb2OFCl, is a new fluoroxychloride mineral found in a specimen from a fumarole formed subsequent to the 1944 eruption of Vesuvius volcano, Naples Province, Italy. It occurs as well-shaped lamellar crystals up to 0.25 × 0.25 × 0.01 mm typically forming clusters up to 0.4 × 0.4 mm on the surface of volcanic scoria in association with anglesite, artroeite, atacamite, calcioaravaipaite, cerussite, challacolloite, cotunnite, hephaistosite, manuelarossiite, matlockite and susannite. Napoliite is colourless with white streak and adamantine lustre. It is brittle and has a laminated fracture. Cleavage is perfect on {001}. Dcalc = 7.797 g cm–3. The calculated mean refractive index is 2.10. Chemical composition (wt.%, electron microprobe) is: PbO 91.71, F 3.89, Cl 7.34, –O=(F+Cl) –3.30, total 99.64. The empirical formula calculated on the basis of 3 anions is Pb1.999O0.997F0.996Cl1.007. Raman spectroscopy confirms the absence of OH– groups and H2O molecules in the mineral. Napoliite is tetragonal, space group P42/mcm, a = 5.7418(11), c = 12.524(4) Å, V = 412.9(2) Å3 and Z = 4. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 3.860 (85) (111); 3.139 (20) (004); 2.914 (100) (113); 2.866 (63) (200); 2.118 (19) (204); 2.027 (19) (220); 1.665 (20) (313); and 1.642 (23) (117). The crystal structure was refined to R1 = 0.024 for 222 reflections with F > 4σ(F). It is based on lead oxide blocks derived from that of litharge PbO, which alternate with layers of chloride ions. Napoliite represents a new structure type with a unique order/disorder pattern of fluorine and oxygen atoms. The new mineral is dimorphous with rumseyite. It is named after the city of Naples (Napoli in Italian).

New Minerals from the Redmond Mine, North Carolina, USA: II. Cubothioplumbite and Hexathioplumbite, Two New Minerals Containing the Cubane-Like [Pb4(OH)4]4+ Structural Unit

Abstract The new minerals cubothioplumbite (IMA2021-091) and hexathioplumbite (IMA2021-092), both with the ideal formula [Pb4(OH)4]Pb(S2O3)3, were found in the Redmond mine, Haywood County, North Carolina, USA, where they occur together in a highly unusual secondary assemblage that comprises a variety of rare Pb-Zn-Cu sulfates, thiosulfates, and carbonates. Cubothioplumbite has the following properties: yellow equant crystals to about 0.5 mm; white streak; adamantine luster; brittle; Mohs hardness 3; conchoidal fracture; no cleavage; 5.748 g/cm3 calculated density; isotropic with n > 2.00. Hexathioplumbite has the following properties: colorless hexagonal prisms to about 1 mm; white streak; adamantine luster; brittle; Mohs hardness 2½; curved fracture; no cleavage; 5.531 g/cm3 calculated density; uniaxial (−) with ω = 2.005(5) and ε = 1.995(5). Electron probe microanalyses provided the empirical formulae [Pb4(OH)4]Pb(S2O3)2.72(SO4)0.28 and [Pb4(OH)4]Pb(S2O3)2.68(SO4)0.32 for cubothioplumbite and hexathioplumbite, respectively. Cubothioplumbite is cubic, Pa, a = 14.9179(13) Å, V = 3319.9(9) Å3, and Z = 8. Hexathioplumbite is hexagonal, P63, a = 10.7213(10), c = 8.6541(6) Å, V = 861.49(17) Å3, and Z = 2. The structures of cubothioplumbite (R1 = 0.0354 for 1090 I > 2σI) and hexathioplumbite (R1 = 0.0791 for 1062 I > 2σI) both contain cubane-like [Pb4(OH)4]4+ structural units.

Murphyite, Pb(TeO4), the Te-Analogue of Raspite, a New Mineral from Tombstone, Arizona, USA

Abstract A new mineral species, murphyite (IMA 2021-107), ideally Pb(TeO4), has been found from the Grand Central mine, Tombstone, Arizona, USA. It occurs as bladed or prismatic crystals on top of a quartz matrix. Associated minerals include chlorargyrite, emmonsite, ottoite, stolzite, scheelite, schieffelinite, quartz, and jarosite. Individual crystals of murphyite are up to 0.20 × 0.05 × 0.05 mm in size. Twinning is common on {100}. Murphyite is colorless to very pale yellow in transmitted light, transparent with white streak and adamantine luster. It is brittle and has a Mohs hardness of ∼3½, with perfect cleavage on {100}. The calculated density is 7.579 g/cm3. Murphyite is insoluble in water or hydrochloric acid. An electron microprobe analysis yielded the empirical formula (based on 4 O apfu): (Pb0.96Fe0.03Mn0.02)Σ1.01[(Te0.61W0.38)Σ0.99O4], which can be simplified to Pb[(Te,W)O4]. Murphyite is the Te-analogue of raspite, Pb(WO4), and represents the first mineral with Te6+ substituting for W6+ over 50%. It is monoclinic with space group P21/a and unit-cell parameters a = 13.6089(3), b = 5.01750(10), c = 5.5767(2) Å, β = 107.9280(10)°, V = 362.302(17) Å3, and Z = 4. Its crystal structure consists of distorted MO6 (M = Te + W) octahedra sharing edges to form zigzag chains running parallel to [010]. These chains are linked together by PbO7 polyhedra. Compared to raspite, the substitution of W6+ by Te6+, which has a smaller ionic radius, results in a noticeable structural change: a significant decrease in MO6 octahedral angle distortion, with a concomitant increase in both MO6 octahedral volume and average Pb–O bond length. The unit-cell volume increases from 358.72(4) Å3 for raspite to 362.302(17) Å3 for murphyite. Raman spectroscopic data show that the major peak ascribable to M–O symmetrical stretching vibrations within the MO6 octahedron is centered at 870 cm−1 for raspite but at 881 cm−1 for murphyite.

New Minerals from the Redmond Mine, North Carolina, USA: I. Redmondite, Hydroredmondite, and Sulfatoredmondite, Three Minerals Containing the Novel [Pb8O2Zn(OH)6]8+ Structural Unit

AbstractThe new minerals redmondite (IMA2021–072), [Pb8O2Zn(OH)6](S2O3)4, hydroredmondite (IMA2021–073), [Pb8O2Zn(OH)6](S2O3)4·2H2O, and sulfatoredmondite (IMA2021–089), [Pb8O2Zn(OH)6](SO4)4·6H2O, were found in the Redmond mine, Haywood County, North Carolina, USA, where they occur together in a highly unusual secondary assemblage that comprises a variety of rare Pb-Zn-Cu sulfates, thiosulfates, and carbonates. The properties of redmondite are as follows: colorless to shades of brown, transparent equant rhombs to about 1 mm; white streak; adamantine luster; brittle; Mohs hardness 2; conchoidal fracture; no cleavage; 5.757 g/cm3 calculated density; biaxial with α = 1.96–1.97, β = 1.97–1.98, γ = 1.97–1.98; extreme dispersion. The properties of hydroredmondite are as follows: colorless, transparent prisms, blades, and tablets up to about 1 mm; white streak; adamantine luster; brittle; Mohs hardness 2; curved and stepped fracture; good cleavages on {101} and ; 5.124 g/cm3 calculated density; biaxial (+) with α = 1.830(5), β = 1.880(calc), γ = 1.950(calc), 2Vmeas = 83(1)°. The properties of sulfatoredmondite are as follows: colorless, transparent wedge-shaped crystals to about 2 mm; white streak; adamantine luster; brittle; Mohs hardness 2; curved, irregular fracture; no cleavage; 5.173 g/cm3 calculated density; biaxial (+), α = 1.780(5), β = 1.850(calc), γ = 1.860(calc), 2Vmeas = 40(3)°; moderate r > v dispersion. Electron probe microanalyses provided the empirical formulae: Pb8.16Zn1.00S6+3.97S2−3.97O20H5.79, Pb8.00Zn1.00S6+4.00S2−4.00O22H9.98, and Pb8.00Zn0.99S6+4.00S2−0.89O29.11H17.98 for redmondite, hydroredmondite, and sulfatoredmondite, respectively. Redmondite is monoclinic, P21/c, a = 9.1672(4), b = 10.6576(4), c = 14.0620(10) Å, β = 101.173(7)°, V = 1347.83(12) Å3, and Z = 2. Hydroredmondite is monoclinic, P21/n, a = 12.5991(9), b = 9.2819(4), c = 12.9774(9) Å, β = 90.443(6)°, V = 1517.57(16) Å3, and Z = 2. Sulfatoredmondite is monoclinic, C2/m, a = 17.294(2), b = 7.3668(9), c = 12.7271(18) Å, β = 110.622(9)°, V = 1517.5(4) Å3, and Z = 2. The crystal structures of redmondite (R1 = 0.0346 for 2061 I > 2σI), hydroredmondite (R1 = 0.0346 for 3022 I > 2σI), and sulfatoredmondite (R1 = 0.0344 for 1661 I > 2σI) are all based on the same [Pb8O2Zn(OH)6]8+ structural unit.

Pohlite, a new lead iodate hydroxide chloride from Sierra Gorda, Chile

AbstractThe new mineral pohlite (IMA2022–043), Pb7(IO3)(OH)4Cl9, was found at La Compania mine, Sierra Gorda, Antofagasta Province, Antofagasta, Chile, where it occurs in cavities in an oxidised portion of a quartz vein in association with massive aragonite and anhydrite. Pohlite crystals are transparent, colourless to pale grey blades, up to 4 mm in length. The mineral has a white streak, adamantine lustre and is nonfluorescent. It is brittle with irregular, conchoidal fracture. The Mohs hardness is ~2½ and it has no cleavage. The calculated density is 5.838(2) g cm–3. Optically, the mineral is biaxial (+) with α < 2.01(est.), β = 2.02 (calc.), γ = 2.05 (calc.); 2V = 60(5)°; moderate r > v dispersion; orientation: Y∧a ≈ 20°, Z∧b ≈ 30°; and is nonpleochroic. The Raman spectrum exhibits bands consistent with IO3– and O–H. Electron microprobe analysis provided the empirical formula Pb6.74I1.00Cl9.29O6.71H4.23. The five strongest powder X-ray diffraction lines are [dobs Å(I)(hkl)]: 3.818(91)(023, 122, 1$\bar{2}$1), 3.674(85)($\bar{1}\bar{2}$1, $\bar{1}$22, 200, 104), 3.399(47)($\bar{2}$10, 210, $\bar{1}$04), 2.378(100)(302, 041, $\bar{2}$24) and 1.9943(45)(multiple). Pohlite is triclinic, P$\bar{1}$, a = 7.3366(5), b = 9.5130(9), c = 16.2434(15) Å, α = 81.592(7), β = 84.955(7), γ = 89.565(6)°, V = 1117.13(17) Å3 and Z = 2. The structure of pohlite (R1 = 0.0328 for 3394 I > 2σI) contains two types of clusters, a [Pb4(OH)3]5+ cluster formed by short Pb–O bonds and a [Pb3(OH)(IO3)]28+ ‘double cluster’ formed by short I–O bonds and short- to medium-length Pb–O bonds. Long Pb–Cl and I–Cl bonds link the clusters together in three dimensions.

Tombstoneite, a new mineral from Tombstone, Arizona, USA, with a pinwheel-like Te6+O3(Te4+O3)3 cluster

AbstractThe new mineral tombstoneite (IMA2021-053), (Ca0.5Pb0.5)Pb3Cu2+6Te6+2O6(Te4+O3)6(Se4+O3)2(SO4)2⋅3H2O, occurs at the Grand Central mine in the Tombstone district, Cochise County, Arizona, USA, in cavities in quartz matrix in association with jarosite and rodalquilarite. Tombstoneite crystals are green pseudohexagonal tablets, up to 100 μm across and 20 μm thick. The mineral has a pale green streak and adamantine lustre. It is brittle with irregular fracture and a Mohs hardness of ~2½. It has one perfect cleavage on {001}. The calculated density is 5.680 g cm–3. Optically, the mineral is uniaxial (–) and exhibits pleochroism: O = green, E = light yellow green; O > E. The Raman spectrum exhibits bands consistent with Te6+O6, Te4+O3, Se4+O3 and SO4. Electron microprobe analysis provided the empirical formula (Ca0.51Pb0.49)Σ1.00Pb3.00Cu2+5.85Te6+2.00O6(Te4+1.00O3)6(Se4+0.69Te4+0.24S0.07O3)2(S1.00O4)2⋅3H2O. Tombstoneite is trigonal, P321, a = 9.1377(9), c = 12.2797(9) Å, V = 887.96(18) Å3 and Z = 1. The structure of tombstoneite (R1 = 0.0432 for 1205 I > 2σI) contains thick heteropolyhedral layers comprising Te6+O6 octahedra, Jahn-Teller distorted Cu2+O5 pyramids, Te4+O3 pyramids and Se4+O3 pyramids. Pb2+ cations without stereoactive 6s2 lone-pair electrons are hosted in pockets in the heteropolyhedral layer. Pb2+ cations, possibly with stereoactive 6s2 lone-pair electrons, are located in the interlayer region along with SO4 tetrahedra and H2O groups. Within the heteropolyhedral layer, the Te6+O6 octahedra and the Te4+O3 pyramids form finite Te6+O3(Te4+O3)3 clusters with a pinwheel-like configuration. This is the first known finite complex including both Te4+ and Te6+ polyhedra in any natural or synthetic tellurium oxysalt structure.

Paradimorphite, β-As4S3, a vintage new mineral from Solfatara di Pozzuoli and Vesuvius, Napoli, Italy

AbstractThe new mineral paradimorphite corresponds to the high temperature polymorph of As4S3, whose existence was supposed by Arcangelo Scacchi in 1850 in the fumaroles at the Solfatara di Pozzuoli, Campi Flegrei, near Napoli, Italy.Crystals of paradimorphite are orange yellow, transparent or semitransparent, with adamantine lustre. Habit is prismatic and observed forms are {110}, {101}, {111}, {100}, {010} and {001}. Tenacity is brittle, no distinct cleavage is observed and fracture is conchoidal. The mineral does not fluoresce in long- or shortwave ultraviolet light. No twinning is apparent. The streak is saffron yellow. Hardness (Mohs) = 1–2. The observed density is 3.510(3) g/cm3, calculated density is 3.500 g/cm3. The mineral is orthorhombic, space group Pnma, with a = 9.1577(7), b = 8.0332(6), c = 10.2005(8) Å, V = 750.41(10) Å3 and Z = 4. The eight strongest powder X-ray diffraction lines are [dobs Å(I)(hkl)]: 6.299(48)(011), 5.186(100)(111), 4.174(31)(201), 3.133(34)(022), 3.116(58)(212), 2.980(41)(122), 1.846 (27)(413) and 1.808(23)(134). The structure was refined to R = 0.0229 for 979 reflections with I >2σ(I). Crystals of paradimorphite contain As4S3 molecules, of idealised C3v symmetry, with the four arsenic atoms in a triangular pyramidal arrangement, with sulfur atom bridges on the three adjacent apical edges. Molecular dimensions and conformation are identical within standard uncertainties with those of the low-temperature polymorph dimorphite. No substantial differences, neither in the molecular packing nor in the molecular orientation, could be observed; minor differences being related to intermolecular distances only.

Flaggite, Pb4Cu2+4Te6+2(SO4)2O11(OH)2(H2O), a new mineral with stair-step-like HCP layers from Tombstone, Arizona, USA

AbstractThe new mineral flaggite (IMA2021-044), Pb4Cu2+4Te6+2(SO4)2O11(OH)2(H2O), occurs at the Grand Central mine in the Tombstone district, Cochise County, Arizona, USA, in cavities in quartz matrix in association with alunite, backite, cerussite, jarosite and rodalquilarite. Flaggite crystals are lime-green to yellow-green tablets, up to 0.5 mm across. The mineral has a very pale green streak and adamantine lustre. It is brittle with irregular fracture and a Mohs hardness of ~3. It has one excellent cleavage on {010}. The calculated density is 6.137 g cm–3. Optically, the mineral is biaxial (+) with α = 1.95(1), β = 1.96(1), γ = 2.00(1) (white light); 2V = 54(2)°; pleochroism:Xgreen,Ylight yellow green,Znearly colourless;X>Y>Z. The Raman spectrum exhibits bands consistent with TeO6and SO4. Electron microprobe analysis provided the empirical formula Pb3.88Cu2+3.89Te6+2.08(SO4)2O11(OH)2(H2O) (–0.03 H). Flaggite is triclinic,P1,a= 9.5610(2),b= 9.9755(2),c= 10.4449(3) Å, α = 74.884(1), β = 89.994(1), γ = 78.219(1)°,V= 939.97(4) Å3andZ= 2. The structure of flaggite (R1= 0.0342 for 5936I> 2σI) contains hexagonal-close-packed, stair-step-like layers comprising TeO6octahedra and Jahn-Teller distorted CuO6octahedra. The layers in the structure of flaggite are very similar to those in bairdite, timroseite and paratimroseite.

Radvaniceite, GeS2, a New Germanium Sulphide, from the Kateřina Mine, Radvanice near Trutnov, Czech Republic

The new mineral radvaniceite, GeS2, was found on the burning coal mine dump of the abandoned Kateřina coal mine at Radvanice, near Trutnov, northern Bohemia, Czech Republic. It occurs as aggregates resembling cotton tufts up to 5 mm in size; they are composed of acicular crystals up to fibres about 1–5 μm thick and up to 3 mm in length. Individual fibres are distorted and partly resemble bent wires nucleated on rock fragments or on black, crumbly ash, in association with minerals of solid solutions of Bi-Sb and stangersite, herzenbergite, and greenockite. Radvaniceite was also observed as irregular grains in a range of 10–50 μm in size, forming part of earlier multicomponent aggregates upon which the above-described crystals grow. These aggregates are formed, in addition to radvaniceite, by minerals of Bi-Sb, Bi2S3-Sb2S3 and Bi2S3-Bi2Se3 solid solutions, Bi3S2, Bi-sulpho/seleno/tellurides, tellurium, unnamed PbGeS3, Cd4GeS6, GeAsS, Sn5Sb3S7, stangersite, greenockite, cadmoindite, herzenbergite, teallite, and Sn- and/or Se-bearing galena. Radvaniceite is formed under reducing conditions by direct crystallization from hot gasses (250–350 °C) containing Cl and F at a depth of 30–60 cm under the surface of a burning coal mine dump; the mine dump fire started spontaneously, and no anthropogenic material was deposited there. Acicular crystals up to fibres of radvaniceite are elastic to flexible; are white to yellowish grey in colour, with white streaks; are translucent in transmitted light; and have vitreous to adamantine lustre. Cleavage and fracture were not observed. The calculated density is 3.05 and 2.99 g·cm−3 for the empirical and ideal formulae, respectively. Radvaniceite is transparent under the microscope, with a very weak pleochroism (from colourless to pale greenish yellow), and has a refraction index > 1.8. Under reflected light, radvaniceite is light grey; bireflectance and pleochroism were not observed due to abundant, white to grey, internal reflections. Anisotropy in crossed polars is distinct with grey rotation tints. Reflectance values of radvaniceite in air (Rmin–Rmax, %) are: 15.4–18.8 at 470 nm, 16.1–20.4 at 546 nm, 16.4–20.8 at 589 nm, and 16.9–20.9 at 650 nm. The empirical formula, based on electron-microprobe analyses, is (Ge0.99Bi0.01)Σ1.00(S1.97Se0.03)Σ2.00. The ideal formula is GeS2, which requires Ge 53.10, S 46.90, total 100 wt. %. Radvaniceite is monoclinic, Pc, a = 6.8831(12), b = 22.501(3), c = 6.8081(11) Å, β = 120.365(9)°, with V = 909.8(4) Å3 and Z = 12. The strongest reflections of the powder X-ray diffraction pattern [d, Å (I) (hkl)] are: 5.7395 (100) (11-1, 110), 5.2067 (16) (021), 3.3650 (33) (111, 11-2), 2.8417 (33) (022), 2.8236 (16) (170, 17-1), 2.8134 (20) (080) and 2.6257 (19) (240, 24-2). According to X-ray powder diffraction data and Raman spectroscopy, radvaniceite is a natural analogue of synthetic monoclinic low-temperature β-GeS2 with distorted GeS4 tetrahedra forming four corner-sharing tetrahedral chains, which are connected by corner-sharing tetrahedra in a three-dimensional structure. We named the mineral after its type locality, Radvanice, one of the past centres of coal mining in the Czech limb of the Intra-Sudetic Basin. This mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (number 2021-052).

Pyradoketosite, a new, unexpected, polymorph of Ag3SbS3 from the Monte Arsiccio mine (Apuan Alps, Tuscany, Italy)

Abstract Although everything seemed clear about the Ag-Sb-S compounds belonging to one of the more deeply studied experimental systems, nature allowed us to discover a new polymorph of Ag3SbS3, which could represent a compound for assessing new technological potentialities. The new mineral species pyradoketosite, Ag3SbS3 (IMA 2019-132), was discovered in the pyrite + baryte + iron oxide ore deposit of the Monte Arsiccio mine, Apuan Alps, Tuscany, Italy. It occurs as brittle orange acicular crystals, up to 200 μm in length and 25 μm in thickness, with adamantine luster. Under reflected light, pyradoketosite is slightly bluish-gray, with abundant orange internal reflections. Bireflectance is weak, and anisotropism was not observed, being masked by abundant internal reflections. Minimum and maximum reflectance data for the wavelengths recommended by the Commission on Ore Mineralogy [Rmin/Rmax (%) (λ, nm)] are 32.8/32.9 (470), 30.2/30.7 (546), 29.0/29.6 (589), and 27.5/28.4 (650). Electron microprobe analysis gave (mean of 6 spot analyses, in wt%): Ag 59.81, Sb 22.63, S 17.78, total 100.22. On the basis of (Ag+Sb) = 4 atoms per formula unit, the empirical formula of pyradoketosite is Ag2.996(11)Sb1.004(11)S2.996(15). Pyradoketosite is monoclinic, space group P21/n, with a = 13.7510(15), b = 6.9350(6), c = 19.555(2) Å, β = 94.807(4)°, V = 1858.3(3) Å3, Z = 12. The crystal structure was solved and refined to R1 = 0.063 on the basis of 2682 unique reflections with Fo > 4σ(Fo) and 191 refined parameters. The structure of pyradoketosite can be described as formed by the alternation of {101} layers: an Sb-rich layer, Sb3AgS3, and two distinct Ag8S6 layers. This layered organization allows identifying structural relationships with the wittichenite-skinnerite pair. Pyradoketosite is associated with pyrargyrite, tetrahedrite-(Hg), valentinite, and probable pyrostilpnite in baryte + dolomite + quartz veins embedded in metadolostone. Its name derives from the old Greek words “πυρ” (fire) and “άδόκητος” (unforeseen), because of the unexpected occurrence of this third polymorph of the compound Ag3SbS3.

Wumuite (KAl<sub>0.33</sub>W<sub>2.67</sub>O<sub>9</sub>) – a new mineral with an HTB-type structure from the Panzhihua–Xichang region in China

Abstract. Wumuite, ideally KAl0.33W2.67O9, is a new mineral species found in the Neoproterozoic Sinian light-weathered biotite–quartz monzonite in the southern part of the Panzhihua–Xichang region (Nanyang village: 26∘46′8.21′′ N, 101∘27′13.86′′ E), China. It is associated with quartz, orthoclase, albite, biotite, hornblende, kaolinite, ilmenite, goethite, hematite, zircon, zoisite, tourmaline, monazite-(Ce), allanite-(Ce), scheelite, tellurite, tewite, and an unidentified, potentially new mineral corresponding to WO3. Wumuite occurs as light green hexagonal tabular crystals, is up to 0.3 mm in diameter, and has a vitreous to adamantine luster and a white streak; i.e., it is transparent. The mineral is brittle with good cleavage parallel to {101¯0} and {0001}. It has a Mohs hardness of about 5–6 and a calculated density of 6.52 g cm−3. Electron microprobe analyses yielded the following (in wt % – average of 10 spot analyses of one sample): K2O 5.55, WO3 91.16, TeO2 0.59, and Al2O3 2.52, with a total of 99.82. The empirical formula for wumuite calculated on the basis of Oapfu=9 is K0.80(W2.68Al0.34Te0.03)∑3.05O9, ideally K(W2.67Al0.33)∑3O9 or KAl0.33W2.67O9. The strongest four diffraction lines [d Å (I) (hkl)] are 6.261(36)(010), 3.727(30)(001), 3.161(100)(020), and 2.413(40)(021). Wumuite is hexagonal, in space group P6/mmm, with a=7.2952(5) Å, c=3.7711(3) Å, V=173.81(2) Å3, and Z=1. The crystal structure was solved and refined to a reliability factor of R1[F2>4σ(F2)]=0.025 (wR2=0.072) based on 164 unique reflections (777 measured reflections, R(int)=0.011). Wumuite has a hexagonal tungsten bronze (HTB)-type structure. The layers of corner-sharing [(W,Al)O]6 octahedra, with the layers oriented normal to the short (3.7713 Å) c repeat and along with the W–O–W links, connect to form a hexagonal ring channel (tunnel). K is distributed in the hexagonal channel. An associated new mineral, tewite, which was discovered in the same area, also has a new tungsten bronze (TB)-type-related structure and has a genetic connection with wumuite in both back-scattered electron (BSE) images and synthetic experiments. The formation of wumuite is likely related to the nearby quartz-vein-type Au mineralization. The mineral was formed by a metasomatic reaction between W-rich hydrothermal fluids and the potassium feldspar in the monzonite.

English

Coarse rutile with some grains exceeding 32 mm was recovered from regolith excavated from three pits (ABC) at Ebensuk. The rutile concentration ranges from 2.53 kg/m3 of regolith material in Pit C to 2.83 kg/m3 in Pit B with an average of 2.66 kg/m3. The rutile is black, longitudinally striated, with a metallic to adamantine luster and hard. Results of grain size (Z) analysis show that the rutile crystals range in size from 4mm to Z≥32 mm. The grains are predominantly concentrated in the 16≤Z 96 wt%, and subordinate Fe2O (2.2-3.1 wt%), and minor amounts of Al2O3, SO3, K2O P2O5 and Mn2O3 for all the samples analyzed, and meets international specifications for economic rutile ores. The rutile must have been derived through weathering of the underlying gneisses and their coarse nature is probably indicative of a possible source from granite pegmatite veins occurring in the gneisses outcropping in the study area. Key words: Coarse rutile, geochemistry, high quality, regolith, grain size.

Northstarite, a new lead-tellurite-thiosulfate mineral from the North Star mine, Tintic, Utah, USA

ABSTRACTNorthstarite, Pb6(Te4+O3)5(S2O3), is a new mineral from the North Star mine, Tintic district, Juab County, Utah, USA. It is an oxidation-zone mineral occuring in a vug in massive quartz-baryte-enargite-pyrite in association with anglesite, azurite, chrysocolla, fluorapatite, plumbogummite, tellurite, zincospiroffite, and the new mineral adanite. Crystals are beige short prisms with pyramidal terminations, up to about 1 mm in length. The mineral is transparent to translucent with adamantine luster, white streak, Mohs hardness 2, brittle tenacity, irregular fracture, and no cleavage. The calculated density is 6.888 g/cm3. Northstarite is uniaxial (–) and nonpleochroic. The Raman spectrum is consistent with the presence of tellurite and thiosulfate groups and the absence of OH and H2O. Electron-microprobe analyses gave the empirical formula Pb5.80Sb3+0.05Te4+5.04S6+1.02S2–1.02O18. The mineral is hexagonal, space group P63, with a = 10.2495(5), c = 11.6677(8) Å, V = 1061.50(13) Å3, and Z = 2. The five strongest X-ray powder diffraction lines are [dobs Å(I)(hkl)]: 3.098(100)(113), 2.957(88)(300), 2.140(42)(223), 1.7335(41)(413), and 1.6256(31)(306). The structure (R1 = 0.033 for 1476 I > 2σI reflections) is a framework constructed of short (strong) Pb–O and Te–O bonds with channels along the 63 axes. The thiosulfate groups at the centers of the channels are only weakly bonded to the framework.

Tancaite-(Ce), ideally FeCe(MoO<sub>4</sub>)<sub>3</sub> ● 3H<sub>2</sub>O: description and average crystal structure

Abstract. Tancaite-(Ce), ideally FeCe(MoO4)3⚫3H2O, is a new mineral occurring within cavities in the quartz veins which cut the granite at Su Seinargiu, Sarroch (CA), Sardinia, Italy. It is a secondary mineral formed in the oxidation zone of a sulfide ore vein. Associated minerals are quartz, muscovite, molybdenite, pyrite, and a mendozavilite-like phase. Tancaite-(Ce) is red or pale brown in colour, with a vitreous to adamantine lustre. Electron microprobe analyses give (wt %) SiO2 0.34, CaO 0.09, Fe2O3 11.29, SrO 0.02, La2O3 5.04, Ce2O3 10.35, Pr2O3 1.07, Nd2O3 3.66, Sm2O3 0.19, ThO2 2.58, UO2 0.17, MoO3 58.62, and H2O (calculated) 7.43, with a sum of 100.85, from which the empirical formula is calculated. The empirical formula Fe1.033+(Ce0.46La0.23Nd0.16Pr0.05Sm0.01U0.01Th0.07)Σ=0.99(Mo2.96Si0.04)Σ=3.00O12⚫3H2O can be simplified as Fe3+(REE)(MoO4)3⚫3H2O and idealized as FeCe(MoO4)3⚫3H2O. The presence of H2O was confirmed by micro-Raman spectrometry (stretching and bending vibrations of O–H). The calculated density is 3.834 g cm−3. The X-ray diffraction pattern of tancaite-(Ce) is characterized by a set of strong reflections, which point to a cubic subcell with a=6.870(1) Å and space group Pm3¯m, plus a set of superstructure reflections. Tancaite-(Ce) displays a new structure type not previously reported in natural and synthetic molybdates. By considering only the strong reflections, it was possible to solve and refine its average structure (R1=0.038 for 192 unique reflections with I>2σ(I)). The crystal structure consists of FeO6 octahedra centred at the origin of the cubic subcell and linked together through MoO4 tetrahedra by corner sharing. The Mo-centred tetrahedra are statistically distributed in four symmetry-related positions, with one-fourth occupancy. In the centre of the cubic unit cell the REE cations exhibit a 6+3 coordination, bonding six oxygen atoms and three H2O molecules, each of them being disorderly distributed in four symmetry-related positions. One of the possible supercells, with a 48-fold volume with respect to the primitive cubic small subcell, corresponded to a rhombohedral lattice, with a≈19.43 and c≈47.60 Å in the hexagonal setting. Several unsuccessful trials were performed to solve the real crystal structure of tancaite, by indexing the additional superstructure reflections and using their intensities to refine an ordered structural model. The new mineral has been approved by the IMA CNMNC (no. 2009-097). The name comes from Giuseppe Tanca, an Italian amateur mineralogist, who discovered the mineral and gave it to us for studying.

Adanite, a new lead-tellurite-sulfate mineral from the North Star mine, Tintic, Utah, and Tombstone, Arizona, USA

ABSTRACTAdanite, Pb2(Te4+O3)(SO4), is a new oxidation-zone mineral from the North Star mine, Tintic district, Juab County, Utah, and from Tombstone, Cochise County, Arizona, USA. The characterization of the species is based principally on North-Star holotype material. Crystals are beige wedge-shaped blades, up to about 1 mm in length, in cockscomb intergrowths. The mineral is transparent with adamantine luster, white streak, Mohs hardness 2½, brittle tenacity, conchoidal fracture, and no cleavage. The calculated density is 6.385 g/cm3. Adanite is biaxial (–), with α = 1.90(1), β = 2.04(calc), γ = 2.08(calc), 2V(meas) = 54(1)°. The Raman spectrum is consistent with the presence of tellurite and sulfate groups and the absence of OH and H2O. Electron-microprobe analyses gave the empirical formula Pb1.89Sb3+0.02Te4+0.98S6+1.04Cl0.02O6.98. The mineral is monoclinic, space group P21/n, with a = 7.3830(3), b = 10.7545(5), c = 9.3517(7) Å, β = 111.500(8)°, V = 690.86(7) Å3, and Z = 4. The four strongest X-ray powder diffraction lines are [dobs Å(I)(hkl)]: 6.744(47), 3.454(80), 3.301(100), and 3.048(73). The structure (R1 = 0.022 for 1906 I > 2σI reflections) contains Te4+O3 pyramids that are joined by short (strong) Pb–O bonds to form sheets. Interlayer SO4 groups link the sheets via long Pb–O and Te–O bonds.

Cuyaite, Ca2Mn3+As3+14O24Cl, a new mineral with an arsenite framework from near Cuya, Camarones Valley, Chile.

AbstractCuyaite (IMA2019-126), Ca2Mn3+As3+14O24Cl, is a new arsenite mineral from near Cuya in the Camarones Valley, Arica Province, Chile. It is associated with anhydrite, native arsenic, arsenolite, calcite, claudetite, ferrinatrite, gajardoite-3R, leiteite, magnesiocopiapite, phosphosiderite, pyrite, realgar and talmessite and formed from the oxidation of As-bearing primary phases and alteration by saline fluids derived from evaporating meteoric water under hyperarid conditions. Cuyaite occurs as pale brown thin needles (elongated on [010]), typically in divergent sprays and subparallel intergrowths. The streak is white. Crystals are transparent with adamantine lustre; subparallel intergrowths exhibit silky lustre. The mineral has Mohs hardness of 2½, is brittle, exhibits no cleavage and has irregular fracture. The calculated density is 4.140 g cm–3. Cuyaite is optically biaxial (–), with α = 1.87(1), β = 1.956(calc) and γ = 1.98(1), determined in white light; 2Vmeas= 60(1)°; and orientation:X=bandY^a= 53° in obtuse β. Electron microprobe analyses provided the empirical formula Ca2.03Mn3+0.95(As3+13.66Sb3+0.65)Σ14.31O24Cl0.88. The six strongest powder X-ray diffraction lines are [dobsÅ(I)(hkl)]: 4.73(45)(111,$\bar{1}$12), 3.162(100)($\bar{3}$14), 3.035(28)(213), 3.004(37)(204), 2.931(90)($\bar{2}$15, 312) and 2.779(28)(020). Cuyaite is monoclinic,Pn,a= 14.7231(6),b= 5.58709(19),c= 17.4185(12) Å, β = 112.451(8)°,V= 1324.23(14) Å3andZ= 2. In the crystal structure of cuyaite (R1= 0.0369 for 2095I> 2σIreflections), AsO3pyramids share O corners to form a ‘loose’ 3D framework; Jahn–Teller distorted Mn3+O6octahedra and CaO8polyhedra link by edges and corners to form columns; the columns also link by edge- and corner-sharing to the AsO3pyramids in the framework; Cl occupies channels along [010] in the framework. The Raman spectrum is consistent with the presence of multiple As3+O3groups.