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Manganrockbridgeite, Mn22+Fe33+(PO4)3(OH)4(H2O), is a new member of the rockbridgeite group, from the Hagendorf-Süd pegmatite, Oberpfalz, Bavaria. It occurs in association with frondelite, kenngottite, hureaulite and hematite. It forms compact intergrowths and clusters of shiny greenish black blades up to 200 µm long and 20 µm wide but only a few micrometres thick. The crystals are elongated on [100] and flattened on {001}, with perfect cleavage parallel to {001}. Individual thin blades are green in transmitted light and red under crossed polars. The calculated density is 3.40 g cm−3. Manganrockbridgeite is biaxial (+/-), with α= 1.795(5), β= 1.805(calc), γ=1.815(5) (white light) and 2V(meas.) = 90(2)∘. The empirical formula from electron microprobe analyses, Mössbauer spectroscopy and crystal structure refinement is (Mn1.072+Fe0.692+Fe0.163+)Σ1.92(Fe3+)2.88(PO4)3(OH)3.64(H2O)1.44. Manganrockbridgeite has monoclinic symmetry with space group P21/m and unit-cell parameters a=5.198(2), b=16.944(5), c=7.451(3) Å, β=110.170(9)∘, V=616.0(4) Å3 and Z=2. The crystal structure was refined using both laboratory and synchrotron single-crystal diffraction data. Whereas other rockbridgeite-group minerals have orthorhombic symmetry with a statistical distribution of 50 % Fe3+ / 50 % vacancies in M3-site octahedra forming face-shared chains along the 5.2 Å axis, monoclinic manganrockbridgeite has full ordering of Fe3+ and vacancies in alternate M3 sites along the 5.2 Å axis.

Pleysteinite, [(H2O)0.5K0.5]2Mn2Al3(PO4)4F2(H2O)10 ⚫ 4H2O, is the aluminium analogue of benyacarite, from the Hagendorf-Süd pegmatite, Oberpfalz, Bavaria, Germany. It was found in specimens of altered zwieselite, in association with nordgauite, fluellite, rockbridgeite, pyrite and columbite. Pleysteinite occurs as isolated and small aggregates of colourless, stubby prisms that are typically 10 to 30 µm wide and up to 100 µm long. The crystals are flattened on {010} and bounded by {111}, {100} and {001} planes. The calculated density is 2.34 g cm−3. Optically, pleysteinite crystals are biaxial (+), with α=1.566(2), β=1.580(2), γ=1.600(2) (measured in white light) and 2V(meas.) = 80(1)∘. The empirical formula from electron microprobe analyses and structure refinement is [(H2O)0.50K0.50]2(Mn1.20Mg0.49Fe0.272+Zn0.05)∑2.01(Al1.63Fe0.203+Ti0.194+)∑2.02(Al0.56Ti0.444+) (PO4)4.02[F0.58O0.31(OH)0.11]2(H2O)10 ⚫ 3.92H2O. Pleysteinite has orthorhombic symmetry, with space group Pbca and unit-cell parameters a = 10.4133(8) Å, b=20.5242(17) Å, c=12.2651(13) Å, V=2621.4(4) Å3 and Z=4. The crystal structure was refined using single-crystal data to wRobs=0.054 for 1692 reflections with I>3σ(I). The crystal structure contains corner-connected linear trimers of Al-centred octahedra that share corners with PO4 tetrahedra to form 10-member rings parallel to (010). K+ cations and water molecules are located in the rings. Additional corner-sharing of the PO4 tetrahedra with Mn(H2O)4O2 octahedra occurs along [010] to complete the 3D framework structure.

Mikecoxite, ideally (CHg4)OCl2, is the first mercury-oxide-chloride-carbide containing a C4– anion coordinated by four Hg atoms (a permercurated methane derivative) to be described as a mineral species. It was found at the McDermitt open-pit mine on the eastern margin of the McDermitt Caldera, Humboldt County, Nevada, U.S.A. It is monoclinic, space group P21/n, Z = 4; a = 10.164(5), b = 10.490(4), c = 6.547(3) Å, V 698.0(5) Å3. Chemical analysis by electron microprobe gave Hg 86.38, Cl 11.58, Br 0.46, C 1.81, sum = 100.23 wt%, and O was detected but the signal was too weak for quantitative chemical analysis. The empirical formula, calculated on the basis of Hg + Cl + Br = 6 apfu, is (C1.19Hg3.39)(Cl2.57Br0.05)Σ2.62, and the ideal formula based on the chemical analysis and the crystal structure is (CHg4)OCl2. The seven strongest lines in the X-ray powder diffraction pattern are [d (Å), I, (hkl)]: 2.884, 100, (230); 2.989, 81, (301, 301, 112, 112, 131, 131); 2.673, 79, (122, 122, 212, 212); 1.7443, 40, (060, 432, 432); 5.49, 34, (101, 101); 4.65, 32, (120); 2.300, 30, (312, 312). The Raman spectrum shows three bands at 638, 675, and 704 cm–1, well above the range characteristic of NHg4 stretching vibrations between 540 and 580 cm–1, that are assigned to CHg4 stretching vibrations. Mikecoxite forms intergrowths of bladed crystals up to 100 μm long that occur on granular quartz or in vugs associated with kleinite. It is black with a submetallic to metallic luster and strong specular reflections and does not fluoresce under short-or long-wave ultraviolet light. Neither cleavage nor parting were observed, and the calculated density is 8.58 g/cm3. In the crystal structure of mikecoxite, (C4–Hg42+) groups link through O2– ions to form three-membered rings that polymerize into corrugated [CHg4OCl]+ layers with near-linear C4––Hg2+–O and C 4––Hg2+–Cl linkages. The layers link in the third direction directly via weak Hg2+–O2– and Hg2+–Cl– bonds to adjacent layers and also indirectly via interlayer Cl–. A bond-valence parameter has been derived for (Hg2+–C4–) bonds: Ro = 2.073 Å, b = 0.37, which gives bond-valence sums at the C4– ions in accord with the valence-sum rule. The source of carbon for mikecoxite in the volcanic high-desert environment of the type locality seems to be methane, with the reaction catalyzed by microbiota through full mercuration of carbon atoms, beyond the first stage that produces the volatile and highly mobile methylmercury, [CH3Hg]+, a potent neurotoxin that accumulates in marine food chains. Both the mineral and the mineral name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA 2021-060). The mineral is named after Michael F. Cox (b. 1958), a founding member of the New Almaden Quicksilver County Park Association (NAQCPA) who was responsible for characterizing and remediating environmental mercury on-site and who recovered the rock containing the new mineral.

Finchite (IMA2017-052), Sr(UO2)2(V2O8)·5H2O, is the first uranium mineral known to contain essential Sr. The new mineral occurs as yellow-green blades up to ~10 µm in length in surface outcrops of the calcrete-type uranium deposit at Sulfur Springs Draw, Martin County, Texas, U.S.A. Crystals of finchite were subsequently discovered underground in the Pandora mine, La Sal, San Juan County, Utah, U.S.A., as diamond-shaped golden-yellow crystals reaching up to 1 mm. The crystal structure of finchite from both localities was determined using single-crystal X-ray diffraction and is orthorhombic, Pcan, with a = 10.363(6) Å, b = 8.498(5) Å, c = 16.250(9) Å, V = 1431.0(13) Å3, Z = 4 (R1 = 0.0555) from Sulfur Springs Draw; and a = 10.3898(16), b = 8.5326(14), c = 16.3765(3) Å, V = 1451.8(4) Å3, Z = 4 (R1 = 0.0600) from the Pandora mine. Electron-probe microanalysis provided the empirical formula (Sr0.88K0.17Ca0.10Mg0.07Al0.03Fe0.02)Σ1.20(UO2)2(V2.08O8)·5H2O for crystals from Sulfur Springs Draw, and (Sr0.50Ca0.28Ba0.22K0.05)Σ0.94(U0.99O2)2(V2.01O8)·5H2O for crystals from the Pandora mine, based on 17 O atoms per formula unit. The structure of finchite contains uranyl vanadate sheets based upon the francevillite topology. Finchite is a possible immobilization species for both uranium and the dangerous radionuclide 90Sr because of the relative insolubility of uranyl vanadate minerals in water.

The 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.

The new mineral alumolukrahnite (IMA2022–059), CaCu2+Al(AsO4)2(OH)(H2O), was found at the Jote mine, Copiapó Province, Chile, where it is a secondary alteration phase associated with conichalcite, coronadite, gypsum, olivenite, pharmacosiderite, rruffite and scorodite. Alumolukrahnite occurs as crude diamond-shaped tablets up to ~0.1 mm, intergrown in crude spherical aggregates. Crystals are apple green and transparent to translucent, with vitreous lustre and a white streak. The Mohs hardness is 3½. The mineral is brittle with irregular fracture and no cleavage. The calculated density is 4.094 g cm–3. Optically, alumolukrahnite is biaxial (+) with α = 1.73(1), β = 1.74(1) and γ = 1.76(1) (white light). The empirical formula, determined from electron microprobe analyses, is Ca1.01(Cu0.92Zn0.13)Σ1.05(Al0.96Fe0.01)Σ0.97(As0.985O4)2(OH)0.88(H2O)1.12. Alumolukrahnite is triclinic, P $\bar{1}$ , a = 5.343(5), b = 5.501(5), c = 7.329(5) Å, α = 67.72(2), β = 69.06(2), γ = 69.42(2)°, V = 180.3(3) Å3 and Z = 1. Alumolukrahnite is a member of the tsumcorite group and is the Al analogue of lukrahnite.

Tomiolloite (IMA2021-019) is a new aluminum tellurite sulfite-sulfate mineral discovered at the Bambolla mine, Moctezuma, Sonora, Mexico, a well-known tellurium (Te) mineral locality. Tomiolloite forms roughly spherical clusters of crystals comprised of very thin, needle-like crystals (1 μm diameter, ~40 μm length) around a core of small, stubbier, broken crystals. Tomiolloite is generally found growing on tellurite or quartz. The strongest powder X-ray diffraction lines are [dobs Å (Iobs) (hkl)]: 11.667 (89) (100), 8.240 (38) (101), 4.107 (29) (202,211,121), 3.223 (100) (203,302,130), and 2.905 (37) (213,123,222,400). The empirical formula of tomiolloite, as determined by electron microprobe analysis, is (Al10.64Te1.016+Fe0.313+Zn0.04)Σ12(Te5.004+Pb0.02)Σ5.02(S0.494+S0.496+Si0.02)Σ1.00O21.53[(OH)20.86Cl0.11]Σ20.97, which is simplified to the ideal formula Al12(Te4+O3)5[(SO3)0.5(SO4)0.5](OH)24. Significant Te6+ substitution for Al3+ is observed in tomiolloite, verified by X-ray photoelectron spectroscopy and crystal-structure analysis. The structure of tomiolloite was determined using synchrotron single-crystal X-ray diffraction, showing that tomiolloite is hexagonal and crystallizes in the space-group P63/m, with the unit-cell parameters a = 13.3360(19) Å, c = 11.604(2) Å, V = 1787.3(6) Å3, and Z = 2. Tomiolloite has a unique microporous framework structure, which bears a slight similarity to that of zemannite, but it has a much larger cavity diameter (8.85 Å). The framework is built from edge-sharing Mφ6 octahedra (M = Al3+ and Te6+), Te4+O3 trigonal pyramids, and Te4+O4 disphenoids. Mφ6 octahedra edge-share to form crankshaft-shaped chains along c, with Te4+On polyhedra filling notches in the crankshafts and providing linkages between adjacent chains. The framework has an overall positive charge, which is balanced by the presence of both sulfite (SO32−) trigonal pyramids and sulfate (SO42−) tetrahedra in the channels.

The new mineral shinarumpite (IMA2021-105), [Co(H2O)6][(UO2)(SO4)2(H2O)]⋅4H2O, was found in the Scenic mine on Fry Mesa, White Canyon district, San Juan County, Utah, USA, where it occurs as a secondary phase on granular quartz matrix in association with gypsum, deliensite, Co-rich rietveldite, scenicite, shumwayite and sulfur. Shinarumpite crystals are transparent, yellow, blades or prisms, up to 1 mm in length. The mineral has white streak, vitreous lustre and is nonfluorescent. It is brittle with irregular, curved fracture. The Mohs hardness is ~2½ and it has a perfect {100} cleavage. The density is 2.58(2) g⋅cm–3. Optically, the mineral is biaxial (–) with α = 1.515(2), β = 1.526(2), γ = 1.529(2) (white light); 2V = 55(1)°; extreme r < v dispersion; orientation: Z = b, X ^ a = 30° in obtuse β; pleochroism: X = very pale yellow, Y = pale yellow, Z = light yellow; X < Y < Z. The Raman spectrum exhibits bands consistent with UO22+, SO42– and O–H. Electron microprobe analysis provided the empirical formula [(Co0.51Ni0.28Fe0.21)Σ1.00(H2O)6][(UO2)(SO4)2(H2O)]⋅4H2O. The five strongest powder X-ray diffraction lines are [dobs Å(I)(hkl)]: 10.37(100)(200), 5.73(43)(111), 5.20(70)(400, 202, 211), 4.70(31)( $\bar{3}$ 11) and 3.326(30)(213, 021). Shinarumpite is monoclinic, P21/c, a = 21.0549(15), b = 6.8708(5), c = 12.9106(5), β = 96.678(7)°, V = 1885.03(17) Å3 and Z = 4. In the structure of shinarumpite (R1 = 0.0336 for 2623 I > 2σI), linkages of pentagonal bipyramids and tetrahedra form an infinite [(UO2)(SO4)2(H2O)]2– sheet. Isolated Co(H2O)6 octahedra and H2O groups occupy the interlayer region linking the sheets via an extensive system of hydrogen bonds. The structure of shinarumpite is very similar to that of leydetite. Uranyl sulfate structural unit types are discussed with respect to frequency and charge deficiency per anion (CDA).

The 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.

Pomite (IMA2021-063), ideally Ca3[V54+V105+O37(CO3)]·37H2O, and pseudopomite (IMA2021-064), ideally Ca3.5[V64+V95+O37(CO3)]·32H2O, are two new polyoxometalate minerals from the Blue Streak mine, Bull Canyon, Montrose County, Colorado, U.S.A. Pomite properties: striated blades up to ~1 mm long; very dark green-blue color; green-blue streak; vitreous luster; brittle; Mohs hardness ≈2; irregular, splintery fracture; good cleavages on {010} and {001}; 2.19(2) g/cm−3 density; refractive indices in the vicinity of 1.70; weakly birefringent with little or no pleochroism. Pseudopomite properties: striated prisms and blades up to ~1 mm; very dark blue-green color; blue-green streak; vitreous luster; brittle; Mohs hardness ≈2; curved, irregular fracture; probably two fair cleavages, {100} and {001}; 2.40(2) g/cm−3 density; refractive indices in the vicinity of 1.72; no discernable birefringence or pleochroism. Electron microprobe analyses provided the empirical formulas Ca3.11[V5.234+V9.775+O37 (CO3)]·37H2O and Ca3.49[V5.984+V9.025+O37(CO3)]·29H2O for pomite and pseudopomite, respectively. Pomite is triclinic, P1, with a = 12.3668(10), b = 12.9692(12), c = 22.068(2) Å, α = 99.038(7), β = 95.689(7), γ = 103.249(7)°, V = 3368.7(5) Å3, and Z = 2. Pseudopomite is triclinic, P1, with a = 12.2910(18), b = 12.6205(15), c = 20.917(3) Å, α = 77.381(6), β = 85.965(5), γ = 64.367(7)°, V = 2853.6(7) Å3, and Z = 2. The crystal structures of both minerals (pomite, R1 = 0.103; pseudopomite, R1 = 0.116) contain a novel [Vx4+V15−x5+O37(CO3)](1+x)– heteropolyanion, which is unique in natural and synthetic materials but has similarities to the [V84+V75+O36(CO3)]7– and [H8V154+O36(CO3)]6– heteropolyanions reported in synthetic phases.

Oldsite (IMA2021-075), ideally K2Fe2+[(UO2)(SO4)2]2(H2O)8, is a new uranyl sulfate mineral found on specimens from the North Mesa Mine group, Temple Mountain, San Rafael district, Emery County, Utah, USA. It is a secondary mineral occurring with alum-(K), halotrichite, metavoltine, quartz, römerite, stanleyite, sulphur, szomolnokite and mathesiusite. It forms rectangular blades flattened on {010} and elongated on [001], reaching ~0.3 mm in length. Crystals are yellow in colour, transparent with a vitreous lustre; the streak is very pale yellow. The mineral is non-fluorescent. Cleavage is excellent on {100} and perfect on {010}; the Mohs hardness is ~2. Crystals are brittle with irregular, splintery fracture. The density measured by flotation in a mixture of methylene iodide and toluene is 3.31 g⋅cm–3; the calculated density is 3.298 g⋅cm–3 for the empirical formula and 3.330 g⋅cm–3 for the ideal formula. Oldsite is biaxial (+), with α = 1.552(2), β = 1.556(2) and γ = 1.588(2) (measured in white light). The 2V measured directly on a spindle stage is 37(1)°; the calculated 2V is 39.6°. Dispersion is r < v, moderate. The optical orientation is X = b, Y = a and Z = c. The mineral is non-pleochroic. The empirical formula of oldsite (on the basis of 28 O apfu) is K1.93(Fe2+0.53Zn0.31V3+0.09Mg0.08)Σ1.02[(U0.98O2)(S1.01O4)2]2(H2O)8. The Raman spectrum is dominated by the vibrations of SO42– and UO22+ units. Oldsite is orthorhombic, Pmn21, a = 12.893(3), b = 8.276(2), c = 11.239(2) Å, V = 1199.2(5) Å3 and Z = 2. The five strongest powder X-ray diffraction lines are [dobs, Å (I, %) (hkl) ]: 8.29 (59) (010), 6.47 (82) (200), 5.10 (62) (210), 4.65 (100) (012, 211) and 3.332 (55) (022, 221). The crystal structure of oldsite was refined from single-crystal X-ray data to R = 0.0258 for 2676 independent observed reflections, with Iobs > 3σ(I). Oldsite is an Fe2+ analogue of svornostite; its crystal structure is based upon infinite chains of uranyl-sulfate polyhedra, which comprises pentagonal UO7 bipyramids sharing four of their equatorial vertices with sulfate tetrahedra such that each tetrahedron is linked to two uranyl bipyramids to form an infinite chain (the free, non-linking equatorial vertex of the uranyl bipyramid is an H2O group). The broader discussion on the origin and composition of uranyl sulfate minerals is made. The new mineral name honours American mineralogist, Dr. Travis A. Olds for his contribution to uranium mineralogy.

Lauraniite, Cu6Cd2(SO4)2(OH)12·5H2O, is a new mineral from the Laurani Mine, Aroma Province, La Paz Department, Bolivia, where it is found as a secondary mineral associated with serpierite and brochantite, on a matrix consisting of tennantite and chalcocite. Lauraniite occurs as bladed crystals up to 110 μm in length. Crystals are pale blue and transparent, with a vitreous luster and a white streak. Fracture is uneven. Cleavage is perfect on {100}. The calculated density is 3.40 g/cm3 based on the empirical formula. Optically, lauraniite is uniaxial (+) with α = 1.637(3), β = 1.638(3), γ = 1.638(3) (white light), 2V = 20(2)°, and orientation Z ≈ a. The empirical formula, based on data obtained from electron microprobe analysis, is Cu6.13(Cd1.62Zn0.24)(SO4)1.96(OH12.03Cl0.05)12.08·5.08H2O. Lauraniite is monoclinic, P21/c, a = 7.3200(15), b = 25.424(5), c = 11.283(2) Å, β = 91.62(3)°, V = 2099.0(7) Å3, and Z = 4. The crystal structure, determined using single-crystal data obtained using synchrotron radiation, refined to R1 = 0.0468% for 5999 observed reflections with Fo > 4σ(Fo). It is characterized by undulating, brucite-like sheets consisting of seven Cuϕ6 (ϕ: O2–, OH–, H2O) octahedra and two Cd(OH)6(H2O) polyhedra. Sheets are decorated on one side by corner-sharing SO4 tetrahedra. Linkages between adjacent sheets are provided by H-bonds.

Matthiasweilite (IMA2021-069), Pb2+Te4+O3, is a new mineral discovered at the Delamar mine, Lincoln County, Nevada, USA. It is a secondary mineral, associated with adanite, choloalite, northstarite, and other oxysalts in a quartz-rich matrix, that developed in an altered primary ore along with altaite, tetrahedrite-(Zn), native gold, and other sulfides and selenides. The mineral occurs as tightly intergrown masses of light yellow crystals. The streak is white, luster is adamantine, Mohs hardness is 2½, tenacity is brittle, and fracture is conchoidal; no obvious cleavage is present. The calculated density is 7.282 g/cm3 for the empirical formula. Data from electron probe microanalysis and assuming O = 3 gives the empirical formula Pb0.99Te4+1.01O3. Matthiasweilite is triclinic, space group P, with cell parameters a = 7.0256(4), b = 10.6345(6), c = 11.9965(8) Å, α = 78.513(6), β = 83.104(6), γ = 84.083(6)°, V = 869.10(9) Å3, and Z = 10. The crystal structure (R1 = 0.0523 for 3416 I > 2σI reflections) consists of Te4+O3 trigonal pyramids that are linked via relatively short (

Pseudodickthomssenite (IMA2021-027), Mg(VO3)2·8H2O, is a new mineral discovered at the Pickett Corral mine, Bull Canyon, Montrose County, Colorado, USA. The mineral formed from the oxidation of montroseite-corvusite assemblages in a moist environment and occurs on asphaltite and on montroseite-corvusite-bearing sandstone in association with dickthomssenite, gypsum, huemulite, lasalite, and trebiskyite. Pseudodickthomssenite is known only from a diverging cluster of striated needles up to about 500 μm long and 20 μm in diameter; the mineral is light tan in color, with a white streak and a silky luster. The crystals are brittle but somewhat flexible in thin fibers. There are two excellent cleavages, {011} and , and the fracture is splintery. The measured density is 1.97(2) g/cm3. Electron probe microanalysis provided the empirical formula [Mg0.99Ca0.01]Σ1.00(V5+O3)2·8H2O. Pseudodickthomssenite is triclinic, P, a = 7.3566(6) Å, b = 9.4672(9) Å, c = 9.5529(9) Å, α = 104.205(7)°, β = 100.786(7)°, γ = 100.157(7)°, V = 616.08(10) Å3, and Z = 2. The structure of pseudodickthomssenite (R1 = 0.0307 for 1124 I > 2σI reflections) contains V5+O5 polyhedra that link by edge-sharing to form a zig-zag [VO3] chain. MgO2(H2O)4 octahedra link the [VO3] chains into a Mg(H2O)4[VO3]4 sheet and the sheets are linked to one another via a complex network of hydrogen bonding involving Mg(H2O)6 octahedra and isolated H2O groups. The structure is very similar to that of dickthomssenite.

Nitroplumbite (IMA2021-045a), [Pb4(OH)4](NO3)4, is a new mineral discovered at the Burro mine, Slick Rock district, San Miguel County, Colorado, USA. It occurs in a secondary efflorescent assemblage on asphaltite and montroseite- and corvusite-bearing sandstone in association with baryte, chalcomenite, and volborthite. The mineral forms as brown equant (pseudocubic) or colorless bladed crystals. The streak is white, luster is vitreous to greasy, Mohs hardness is 2½, tenacity is brittle, and fracture is conchoidal. Nitroplumbite is optically biaxial (–) with α = 1.790(5), β =1.820 (est.), and γ = 1.823 (est.) (white light); 2Vmeas = 35(1)°; optical orientation: Z = b; nonpleochroic. The calculated density is 5.297 g/cm3 for the empirical formula. Electron probe microanalysis provided the empirical formula Pb4.18(OH)4(N0.98O3)4. Nitroplumbite is monoclinic, space group Ia, a = 18.3471(7), b = 17.3057(4), c = 18.6698(8) Å, β = 91.872(3)°, V = 5924.7(4) Å3, and Z = 16. The crystal structure (R1 = 0.0509 for 11161 I > 2σI reflections) is the same as that previously determined for its synthetic analogue. It consists of isolated, internally bonded cubane-like [Pb4(OH)4]4+ clusters and isolated (NO3)– groups that are linked together by long Pb–O bonds and hydrogen bonds.

The 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.

Tomsquarryite, NaMgAl3(PO4)2(OH)6 ⚫ 8H2O, is a new secondary phosphate mineral from Tom's phosphate quarry, Kapunda, South Australia. It occurs as colourless, talc-like hexagonal platelets, with diameters of a few tens of micrometres when formed from the decomposition of minyulite and as thicker (∼ 10 µm) hexagonal crystals when formed from alteration of gordonite. Associated minerals are penriceite, elliottite, minyulite, angastonite and wavellite. The calculated density is 2.22 g cm−3. Tomsquarryite crystals are uniaxial (+) with ω=1.490(3), ε=1.497(3) (white light). Dispersion was not observed. The partial orientation is Z≈c. Electron microprobe analyses of the holotype specimen give the empirical formula Na1.02K0.02Ca0.08Mg1.26Al2.86(PO4)2.00(OH)3.82F2.48 ⚫ 7.70H2O, based on 22 anions. Tomsquarryite belongs to the trigonal crystal system, space group R–3m, with hexagonal unit-cell parameters a=6.9865(5) Å, c=30.634(3) Å and V=1294.9(4) Å3 and with Z=3. The crystal structure was refined using single-crystal diffraction data; R1=0.069 for 303 reflections with I>2σ(I) to a resolution of 0.80 Å. The crystal structure is a derivative of the crandallite structure, with Ca2+ cations replaced by hydrated magnesium ions, [Mg(H2O)6]2+, resulting in an expansion of the interlayer separation from 5.4 Å in crandallite to 10.2 Å in tomsquarryite. The results for tomsquarryite are compared with those for the chemically and structurally related minerals penriceite and elliottite.

Håleniusite-(Ce) (IMA2021-042), CeOF, is a new mineral discovered in ejectum from the Água de Pau volcano, Sãn Miguel Island, Azores District, Portugal. It occurs as opaque, cream-colored, fine-grained pseudomorphic replacements of hexagonal tablets of bastnäsite-(Ce). It is associated with astrophyllite and fluornatropyrochlore in a matrix composed mainly of albite, quartz, and aegirine. The mineral has a white streak and a calculated density of 5.890 g/cm3 for the empirical formula. The strongest powder diffraction lines are [dobsÅ(Iobs)(hkl)]: 3.247(100)(111), 2.840(31)(200), 2.004(46)(220), and 1.705(42)(311). Electron probe microanalysis provided the empirical formula (Ce0.41La0.21Sm0.15Nd0.04Eu0.03Ca0.02Y0.02Dy0.02Gd0.01)Σ0.91(O0.70F0.30)F1.00. Håleniusite-(Ce) has a fluorite-type structure, space group Fmm, with a = 5.6597(10) Å and V = 181.29(10) Å3 (Z = 4).

The new mineral nafeasite (IMA2021-103), NaFe3+(AsO3OH)2⋅H2O, was found at the Torrecillas mine, Iquique Province, Chile, where it is a secondary alteration phase associated with anhydrite, gypsum, halite, lavendulan, magnesiokoritnigite and natrojarosite. Nafeasite occurs in tightly intergrown aggregates of equant crystals. Crystals are light to medium pink and transparent, with vitreous lustre and white streak. The Mohs hardness is ~2½. The density is 3.23(2) g⋅cm–3. Optically, nafeasite is biaxial (+), with α = 1.679(3), β = 1.682(3), γ = 1.730(5) (white light); 2V = 27(2)°; and slight r < v dispersion. The empirical formulae of the holotype and cotype (based on 9 O atoms per formula unit) are Na0.98K0.02Fe0.92Al0.07As2.00O9H4.01 and Na0.97Fe0.68Al0.33As2.00O9H4.01, respectively. Nafeasite is monoclinic, space group C2, with cell parameters: a = 18.6876(16), b = 8.6769(7), c = 14.8100(10) Å, β = 105.238 (5)°, V = 2317.0(3) Å3 and Z = 12. The structure, refined to R1 = 5.03% for 5979 Io > 2σI reflections, is based on a loose 3D framework of alternating AsO3OH tetrahedra and Fe3+O6 octahedra.

Protocaseyite, [Al4(OH)6(H2O)12][V10O28]·8H2O, is a new mineral (IMA2020-090) occurring in low-temperature, post-mining, secondary mineral assemblages at the Burro mine, Slick Rock district, San Miguel County, Colorado, U.S.A. Crystals of protocaseyite are saffron-yellow, thick blades, with pale orange-yellow streak, vitreous luster, brittle tenacity, curved fracture, two very good cleavages, a Mohs hardness of 2, and a density of 2.45(2) g/cm3. The optical properties of protocaseyite could be only partly determined: biaxial with α = 1.755(5), β < 1.80, γ > 1.80 (white light); pleochroic with X and Y yellow, Z orange (X ≈ Y < Z). Electron-probe microanalysis and crystal-structure solution and refinement provided the empirical formula [(Al3.89Mg0.11Ca0.02)Σ4.02(OH)6(H2O)12][H0.06V10O28]·8H2O. Protocaseyite is triclinic, P1, a = 9.435(2), b = 10.742(3), c = 11.205(3) Å, α = 75.395(7), β = 71.057(10), γ = 81.286(6)°, V = 1036.4(5) Å3, and Z = 1. The crystal structure (R1 = 0.026 for 4032 Io>2 σI reflections) contains both the [V10O28]6− decavanadate polyoxoanion and a novel [Al4(OH)6(H2O)12]6+ polyoxocation.

Nitscheite (IMA2020-078), (NH4)2[(UO2)2(SO4)3(H2O)2]·3H2O, is a new mineral species from the Green Lizard mine, Red Canyon, San Juan County, Utah, U.S.A. It is a secondary phase found in association with chinleite-(Y), gypsum, pyrite, and Co-rich rietveldite. Nitscheite occurs in subparallel and divergent intergrowths of yellow prisms, up to about 0.3 mm in length. Crystals are elongated on [101] and exhibit the forms {100}, {010}, {001}, and {111}. The mineral is transparent with vitreous luster and very pale-yellow streak. It exhibits bright green fluorescence under a 405 nm laser. The Mohs hardness is ~2. The mineral has brittle tenacity, curved fracture, and one good cleavage on {010}. The measured density is 3.30(2) g·cm−3. The mineral is easily soluble in H2O at room temperature. The mineral is optically biaxial (–), α = 1.560(2), β = 1.582(2), γ = 1.583(2) (white light); 2Vmeas = 17(1)°; no dispersion; orientation X = b, Z ≈ [101]; pleochroism X colorless, Y and Z yellow; X < Y ≈ Z. Electron microprobe analysis provided the empirical formula (NH4)1.99U2.00S3.00O21H10.01. Nitscheite is monoclinic, P21/n, a = 17.3982(4), b = 12.8552(3), c = 17.4054(12) Å, β = 96.649(7)°, V = 3866.7(3) Å3, and Z = 8. The structure (R1 = 0.0329 for 4547 I > 3σI reflections) contains [(UO2)2(SO4)3(H2O)2]2− uranyl-sulfate sheets, which are unique among minerals, with NH4 and H2O groups between the sheets.

The new mineral scenicite (IMA2021-057), [(UO2)(H2O)2(SO4)]2⋅3H2O, was found in the Green Lizard, Giveaway–Simplot, Markey and Scenic mines, White Canyon district, San Juan County, Utah, USA, where it occurs as a secondary phase on granular quartz matrix in association with various combinations of deliensite, gypsum, natrozippeite, rietveldite and shumwayite. Scenicite crystals are transparent, light green yellow, poorly formed blades or prisms, up to 0.1 mm in length. The mineral has white streak and vitreous lustre. It exhibits bright greenish-white fluorescence (405 nm laser). It is brittle with irregular, curved fracture and a Mohs hardness of ~2. It has excellent {100} and good {001} cleavages. The calculated density is 3.497 g cm–3. Optically, the mineral is biaxial (–) with α = 1.556(2), β = 1.573(2), γ = 1.576(2) (white light); 2V = 45(3)°; extreme r < v dispersion; orientation: X = c, Y = a, Z = b; pleochroism: X and Y = colourless, Z = light green–yellow; and X = Y < Z. The Raman spectrum exhibits bands consistent with UO22+, SO42– and O–H. Electron microprobe analysis provided the empirical formula U1.996S2.005O19H13.997. The five strongest powder X-ray diffraction lines are [dobs Å(I)(hkl)]: 7.69(70)(201), 5.63(100)(111), 4.92(84)(202,310), 4.80(93)(401) and 3.398(55)(020,120,511,601). Scenicite is orthorhombic, Pca21, a = 21.2144(15), b = 6.8188(3) c = 11.2554(6) Å, V = 1628.18(16) Å3 and Z = 4. In the structure of scenicite (R1 = 0.0365 for 1259 I > 2σI), linkages of pentagonal bipyramids and tetrahedra form an infinite neutral [(UO2)(SO4)(H2O)2] chain. The structure of shumwayite contains topologically identical chains.

Philipsburgite has been redefined as the intermediate member of the goldhillite–philipsburgite–kipushite isomorphous series with the ideal formula Cu5Zn[(AsO4)(PO4)](OH)6⋅H2O due to the site-selective As–P substitution. The new mineral goldhillite, ideally Cu5Zn(AsO4)2(OH)6⋅H2O [or Cu5Zn(AsO4)(AsO4)(OH)6⋅H2O], is the arsenate end-member of this series. Goldhillite occurs on fracture surfaces in a rock comprised mostly of quartz with iron hydroxides in association with mixite, cornwallite and conichalcite. Goldhillite forms transparent, bright emerald-green, tabular crystals with vitreous lustre, flattened on {100}, up to 1 mm across and in rosettes up to 1.5 mm. The mineral is brittle with uneven fracture and perfect cleavage on {100}; the Mohs hardness is 3.5. The calculated density for the holotype is 4.199 g cm–3. The Raman spectrum is consistent with the presence of H2O-molecules, OH-groups, AsO4 tetrahedra and traces of PO4. Electron microprobe analyses of goldhillite (H2O content based on the crystal structure) provided: CuO 48.91, ZnO 13.18, As2O5 26.06, P2O5 3.25, H2O 8.97, total 100.37 wt.%. The empirical formula for goldhillite based on O = 15 apfu is (Cu4.69Zn1.23)Σ5.92(As0.86P0.18O4)2(OH)5.61⋅H2O. The crystal structures of goldhillite and philipsburgite were determined using single-crystal X-ray diffraction data and refined to R1 = 0.054 (for 2365 I > 2σI reflections) and 0.052 (for 2308 I > 2σI reflections), respectively. Goldhillite is monoclinic, P21/c, a = 12.3573(5), b = 9.2325(3), c = 10.7163(4) Å, β = 97.346(4)°, V = 1212.59(8) Å3 and Z = 4. Philipsburgite is monoclinic, P21/c, a = 12.3095(9), b = 9.2276(3), c = 10.7195(3) Å, β = 97.137(7)°, V = 1208.16(10) Å3 and Z = 4. The strongest lines of the powder X-ray diffraction pattern of goldhillite [d, Å (I, %)(hkl)] are: 4.09 (28)(300), 3.41 (23)(12$\bar{2}$, 221, 311), 2.57 (100)(132, 11$\bar{4}$, 20$\bar{4}$), 2.17 (18)(42$\bar{3}$, 332), 1.95 (22)(432) and 1.54 (20)(13$\bar{6}$, 060). Goldhillite is named after its type locality, the Gold Hill mine, Tooele County, Utah, USA.

Donowensite (IMA2020-067), Ca(H2O)3Fe3+2(V2O7)2, and mikehowardite (IMA2020-068), Fe3+4(VO4)4(H2O)2·H2O, are intimately associated new secondary minerals from the Wilson Springs vanadium mine, Wilson Springs, Arkansas, USA. Donowensite has the following properties: needles up to 1 mm in length; yellow color; orange streak; subadamantine luster; brittle; Mohs hardness 3; splintery fracture; three cleavages ({001} perfect, {100} and {010} very good); density 2.97(2) g/cm3; biaxial (+), α > 1.95, β > 1.95, γ > 1.95; 2V = 72(2)°; moderate r > v dispersion; orientation X ^ b = 7°, Z ≈ c; pleochroism X brown orange, Y orange yellow, Z yellow. Mikehowardite has the following properties: equant prisms up to 0.15 mm in length; very dark brown color; yellow-orange streak; subadamantine luster; Mohs hardness 3½; irregular, stepped fracture; three cleavages ({100} very good, two undetermined good cleavages); density 3.19(2) g/cm3; biaxial with slight pleochroism in shades of brown-orange; Gladstone-Dale nav = 2.034. Electron probe microanalyses provided the empirical formulae Ca0.93Fe3+1.92Mn3+0.01V4.06P0.01O17H6.00 for donowensite and K0.11Ca0.02Fe3+3.78Mn3+0.03V3.67P0.33O18.87H6.18 for mikehowardite. Donowensite is triclinic, P with a = 7.3452(4), b = 9.9291(4), c = 10.0151(7) Å, α = 94.455(7), β = 98.476(7), γ = 100.779(7)°, V = 705.52(7) Å3, and Z = 2. Mikehowardite is triclinic, P with a = 6.6546(17), b = 6.6689(14), c = 9.003(2) Å, α = 76.515(5), β = 84.400(6), γ = 75.058(5)°, V = 375.11(15) Å3, and Z = 1. The structure of donowensite (R1 = 0.0561 for 2615 I > 2σI reflections) contains zig-zag chains of edge-sharing FeO6 octahedra that are linked to one another by V2O7 pyrovanadate groups to form sheets between which are Ca2+ cations and H2O groups. The structure of mikehowardite (R1 = 0.0678 for 1098 I > 2σI reflections) has similarities to the structure of schubnelite. In both mikehowardite and schubnelite, edge-sharing dimers of Fe3+O6 octahedra are linked by distorted VO4 tetrahedra.

Kingsgateite, ZrMo6+2O7(OH)2⋅2H2O, is a new supergene mineral from the Old 25 Pipe, Kingsgate, Gough Co., New South Wales, Australia. The mineral occurs in cavities in a quartz, muscovite matrix associated with molybdenite, gelosaite and mambertiite. It forms yellowish green to bluish grey, square tabular crystals to 0.12 mm across. Kingsgateite has a white streak and a vitreous lustre. Cleavage was not observed and the fracture is uneven. The calculated density is 3.74 g/cm–3 based on the empirical formula. Kingsgateite is optically biaxial (+), the calculated indices of refraction are α = 1.88, β = 1.89, γ = 1.96 and 2Vcalc = 42.6°. The pleochroism is X = light orange, Y = light yellow and Z = red brown; Y < X < Z. The mineral is tetragonal, space group I41cd, a = 11.4626(16), c = 12.584(3) Å, V = 1653.4(6) Å3 and Z = 8. Electron microprobe analysis yielded ZrO2 23.09, UO2 1.14, ThO2 0.76, FeO 0.62, MoO3 59.27, P2O5 0.29, SO3 1.25, Cl 0.16, H2O 11.62, O=Cl –0.04, total 98.16 wt.%. The empirical formula on the basis of 11 anions per formula unit is Zr0.88U6+0.02Th0.01Fe2+0.04Mo6+1.94S0.07P0.02O6.90Cl0.02OH2.08⋅2.00H2O. The crystal structure of kingsgateite, refined using synchrotron single-crystal data [R1 = 4.53% for 1159 reflections with Fo > 4σ(Fo)], is a framework of edge- and corner-sharing ZrO5(OH)2 pentagonal bipyramids and MoO4(OH)(H2O) octahedra. Kingsgateite is isostructural with the synthetic compound ZrMo6+2O7(OH)2⋅2H2O.

The 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.

A reinvestigation of the type angastonite specimen from the Penrice marble quarry, South Australia, shows that the published powder X-ray diffraction pattern for the mineral corresponds to a mixture of crystalline phases plus an amorphous phase. The published formula for the mineral, CaMgAl2(PO4)2(OH)4⋅7H2O, has been found to correspond to the amorphous phase. A proposal for the redefinition of angastonite as an amorphous phase has been approved by the IMA CNMNC. Amorphous angastonite is isotropic with an index of refraction in the range 1.33 to 1.40 and a measured density of 1.57(2) g cm−3. It is formed from incongruent leaching of minyulite in circulating Mg- and Ca-bearing solutions. The amorphous phase undergoes local recrystallisation to form penriceite and two other new crandallite-derivative layer phases. A cluster model for the local structure in the amorphous mineral is proposed based on crandallite-type segments. A brief review of amorphous minerals is given.

The decavanadate isopolyanion, [V10O28]6–, is a constituent of pascoite-family vanadate minerals and synthetic materials, and both protonated, [HxV10O28](6–x)–, and mixed-valence, [V4+xV5+10–x)O28](6+x)–, varieties have been described. Here we analyze the interaction between the interstitial complex and the decavanadate structural unit using the principle of correspondence of Lewis acidity-basicity. The Lewis base strengths of the decavanadate polyanions vary from 0.054 to 0.154 vu and [V10O28] structures can form from the simple cations Cs+, Rb+, K+, Tl+, and Na+; simple cations with higher Lewis acidities are too acid to form structures. Cations may bond to transformer (H2O) groups to form polyatomic cations that have lower Lewis acidities than the corresponding simple cation. The occurrence of the polyatomic cation {(V5+O2)Al10(OH)20(H2O)18}11+ in caseyite shows the potential for decavanadate phases to incorporate large heteropolycations into their structures. In turn, this suggests that the [V10O28] polyanions may be used to induce co-crystallization of large aqueous polyatomic cations, thus facilitating their structural characterization. There is an inverse relation between the amount of (H2O) in the interstitial complex and the number of bonds between interstitial simple cations and the O2– ions of the vanadate units, and there is a strong correlation between the unit-cell volume per decavanadate unit and the number of (H2O) groups.

Gunterite was originally assigned the ideal formula Na4[H2V10O28]·22H2O. More detailed bond-valence analysis brought into question the presence of a protonated decavanadate anion, which led to the reexamination of the mineral. Infrared spectroscopy confirmed the absence of NH4. Reinterpretation of the original crystal structure data and new electron-probe microanalyses support the redefinition of gunterite as having the ideal formula Na4Ca[V10O28]·20H2O. This redefinition has been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association.

Synthetic and naturally occurring forms of tricopper orthotellurate, CuII 3TeVIO6 (the mineral mcalpineite) have been investigated by 3D electron diffraction (3D ED), X-ray powder diffraction (XRPD), Raman and infrared (IR) spectroscopic measurements. As a result of the diffraction analyses, CuII 3TeVIO6 is shown to occur in two polytypes. The higher-symmetric CuII 3TeVIO6-1C polytype is cubic, space group Ia 3, with a = 9.537 (1) Å and V = 867.4 (3) Å3 as reported in previous studies. The 1C polytype is a well characterized structure consisting of alternating layers of CuIIO6 octahedra and both CuIIO6 and TeVIO6 octahedra in a patchwork arrangement. The structure of the lower-symmetric orthorhombic CuII 3TeVIO6-2O polytype was determined for the first time in this study by 3D ED and verified by Rietveld refinement. The 2O polytype crystallizes in space group Pcca, with a = 9.745 (3) Å, b = 9.749 (2) Å, c = 9.771 (2) Å and V = 928.3 (4) Å3. High-precision XRPD data were also collected on CuII 3TeVIO6-2O to verify the lower-symmetric structure by performing a Rietveld refinement. The resultant structure is identical to that determined by 3D ED, with unit-cell parameters a = 9.56157 (19) Å, b = 9.55853 (11) Å, c = 9.62891 (15) Å and V = 880.03 (2) Å3. The lower symmetry of the 2O polytype is a consequence of a different cation ordering arrangement, which involves the movement of every second CuIIO6 and TeVIO6 octahedral layer by (1/4, 1/4, 0), leading to an offset of TeVIO6 and CuIIO6 octahedra in every second layer giving an ABAB* stacking arrangement. Syntheses of CuII 3TeVIO6 showed that low-temperature (473 K) hydrothermal conditions generally produce the 2O polytype. XRPD measurements in combination with Raman spectroscopic analysis showed that most natural mcalpineite is the orthorhombic 2O polytype. Both XRPD and Raman spectroscopy measurements may be used to differentiate between the two polytypes of CuII 3TeVIO6. In Raman spectroscopy, CuII 3TeVIO6-1C has a single strong band around 730 cm−1, whereas CuII 3TeVIO6-2O shows a broad double maximum with bands centred around 692 and 742 cm−1.

Celleriite, ☐(Mn22+Al)Al6(Si6O18)(BO3)3(OH)3(OH), is a new mineral of the tourmaline supergroup. It was discovered in the Rosina pegmatite, San Piero in Campo, Elba Island, Italy (holotype specimen), and in the Pikárec pegmatite, western Moravia, Czech Republic (co-type specimen). Celleriite in hand specimen is violet to gray-blue (holotype) and dark brownish-green (co-type) with a vitreous luster, conchoidal fracture, and white streak. Celleriite has a Mohs hardness of ~7 and a calculated density of 3.13 and 3.14 g/cm3 for holotype and its co-type, respectively. In plane-polarized light in thin section, celleriite is pleochroic (O = pale violet and E = light gray-blue in holotype; O = pale green and E = colorless in co-type) and uniaxial negative. Celleriite has trigonal symmetry: space group R3m, Z = 3, a = 15.9518(4) and 15.9332(3) Å, c = 7.1579(2) and 7.13086(15) Å, V = 1577.38(9) and 1567.76(6) Å3 for holotype and co-type, respectively (data from single-crystal X-ray diffraction). The crystal structure of the holotype specimen was refined to R1 = 2.89% using 1696 unique reflections collected with MoKα X-ray intensity data. Structural, chemical, and spectroscopic analyses resulted in the formulas: x ( ◻ 0.58 N a 0.42 ) Σ 1.00 Y ( M n 1.39 2 + F e 0.16 2 + M g 0.01 A l 1.14 F e 0.01 3 + L i 0.28 T i 0.01 ) Σ 3.00 Z A l 6 [ T ( S i 5.99 A l 0.01 ) Σ 6.00 O 18 ] ( B O 3 ) 3 ( O H ) 3 w [ ( O H ) 0.65 F 0.03 O 0.32 ] Σ 1.00 ( for holotype ) and x ( ◻ 0.51 N a 0.49 ) Σ 1.00 Y ( M n 0.90 2 + F e 0.50 2 + A l 1.36 F e 0.04 3 + L i 0.17 Zn 0.04 ) Σ 3.00 Z A l 6 [ T ( S i 5.75 B 0.25 ) Σ 6.00 O 18 ] ( B O 3 ) 3 ( O H ) 3 w [ ( O H ) 0.35 F 0.17 O 0.48 ] Σ 1.00 ( for co-type ) Celleriite is a hydroxy species belonging to the X-site vacant group of the tourmaline supergroup. The new mineral was approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association, proposal no. 2019-089. In the Rosina pegmatite, celleriite formed an overgrowth at the analogous pole of elbaite–fluorelbaite–rossmanite crystals during the latest stage of evolution of pegmatite cavities after an event of a pocket rupture. In the Pikárec pegmatite, celleriite occurs as an intermediate growth sector of elbaite, princivalleite, and fluor-elbaite.

Relianceite-(K), K4Mg(V4+O)2(C2O4)(PO3OH)4(H2O)10, is a new mineral species from the Rowley mine, Maricopa County, Arizona, USA. It occurs in an unusual bat-guano-related, post-mining assemblage of phases. Other secondary minerals associated with relianceite-(K) are antipinite, dendoraite-(NH4), fluorite, mimetite, mottramite, rowleyite, salammoniac, struvite, vanadinite, willemite, wulfenite and at least one other new mineral. Crystals of relianceite-(K) are sky blue prisms up to ~0.1 mm in length. The streak is very pale blue and lustre is vitreous, Mohs hardness is 2½, tenacity is brittle and fracture is splintery. The calculated density is 2.111 g⋅cm–3. Relianceite-(K) is optically biaxial (+) with α = 1.528(2), β = 1.529(2), γ = 1.562(2) (white light); 2Vmeas = 22(1)°; orientation Z = b; pleochroism: X = colourless, Y = pale blue, Z = pale blue; X < Y ≈ Z. Electron microprobe analysis gave the empirical formula [K2.21(NH4)1.79]Σ4.00Mg0.96(V4+0.95O)2(C2O4)[P1.03O3.03(OH)0.97]4(H2O)10, with the C, N and H contents constrained by the crystal structure. Raman spectroscopy confirmed the presence of NH4 and C2O4. Relianceite-(K) is monoclinic, Pc, with a = 12.404 (7) Å, b = 9.014 (6), c = 13.260 (8) Å, β = 100.803(10)°, V = 1456 (2) Å3 and Z = 2. The structural unit in the crystal structure of relianceite-(K) (R1 = 0.0540 for 3751 Io > 2σI reflections) is a (V4+O)2(C2O4)(PO3OH)4 chain in which VO6 octahedra are bridged by an oxalate group to form [V2C2O12] dimers, PO3OH tetrahedra form a double bridge between the VO6 octahedra of the dimers, and additional PO3OH tetrahedra decorate the chain. Topologically, this is the same chain found in the structure of davidbrownite-(NH4). The MgO(H2O)5 octahedron can be considered a distant decoration on the chain. The chains are linked to each other through an extensive system of K/NH4–O bonds and hydrogen bonds.

The new mineral paramarkeyite (IMA2021-024), Ca2(UO2)(CO3)3⋅5H2O, was found in the Markey mine, San Juan County, Utah, USA, where it occurs as a secondary phase on gypsum-coated asphaltum in association with andersonite, calcite, gypsum and natromarkeyite. Paramarkeyite crystals are transparent, pale green-yellow, striated tablets, up to 0.11 mm across. The mineral has white streak and vitreous lustre. It exhibits moderate bluish-white fluorescence (405 nm laser). It is very brittle with irregular, curved fracture and a Mohs hardness of 2½. It has an excellent {100} cleavage and probably two good cleavages on {010} and {001}. The measured density is 2.91(2) g cm–3. Optically, the mineral is biaxial (–) with α = 1.550(2), β = 1.556(2), γ = 1.558(2) (white light); 2V = 60(2)°; strong r > v dispersion; orientation: Y = b; nonpleochroic. The Raman spectrum exhibits bands consistent with UO22+, CO32– and O–H. Electron microprobe analysis provided the empirical formula (Ca1.83Na0.20Sr0.03)Σ2.05(UO2)(CO3)3⋅5H2O (+0.07 H). Paramarkeyite is monoclinic, P21/n, a = 17.9507(7), b = 18.1030(8), c = 18.3688(13) Å, β = 108.029(8)°, V = 5676.1(6) Å3 and Z = 16. The structure of paramarkeyite (R1 = 0.0647 for 6657 I > 2σI) contains uranyl tricarbonate clusters that are linked by Ca–O polyhedra to form heteropolyhedral layers. The structure of paramarkeyite is very similar to those of markeyite, natromarkeyite and pseudomarkeyite.

Dendoraite-(NH4), (NH4)2NaAl(C2O4)(PO3OH)2(H2O)2, is a new mineral species from the Rowley mine, Maricopa County, Arizona, USA. It occurs in an unusual bat-guano-related, post-mining assemblage of phases that include a variety of vanadates, phosphates, oxalates and chlorides, some containing NH4+. Other secondary minerals found in association with dendoraite-(NH4) are antipinite, fluorite, mimetite, mottramite, relianceite-(K), rowleyite, salammoniac, struvite, vanadinite, willemite, wulfenite and at least one other new mineral. Crystals of dendoraite-(NH4) are colourless blades up to ~0.1 mm in length. The streak is white and lustre is vitreous, Mohs hardness is 2½, tenacity is brittle and fracture is splintery. The calculated density is 2.122 g⋅cm–3. Dendoraite-(NH4) is optically biaxial (–) with α = 1.490(5), β = 1.540(5) and γ = 1.541(5) (white light); 2Vcalc = 15.7°; and orientation X = b. Electron microprobe analysis gave the empirical formula [(NH4)1.48K0.52]Σ2.00Na0.96(Al0.96Fe3+0.03)Σ0.99(C2O4)[PO2.97(OH)1.03]2(H2O)2, with the C, N and H contents constrained by the crystal structure. Dendoraite-(NH4) is monoclinic, P21/n, with a = 10.695(6), b = 6.285(4), c = 19.227(12) Å, β = 90.933(10)°, V = 1292(2) Å3, and Z = 4. The structural unit in the crystal structure of dendoraite-(NH4) (R1 = 0.0467 for 1322 Io > 2σI reflections) is a double-strand chain of corner-sharing AlO6 octahedra and PO3OH tetrahedra decorated by additional PO3OH tetrahedra and C2O4 groups. Topologically, this is the same chain found in the structure of thebaite-(NH4). The decorated chains connect to one another through links to NaO7(H2O) polyhedra to form a [Na(H2O)Al(C2O4)(PO3OH)2]2– sheet, which connect to one another through bonds to (NH4)/K and through hydrogen bonds.

Whiteite-(CaMnFe), CaMn2+Fe22+Al2(PO4)4(OH)2 ⋅ 8H2O, is a new whiteite-subgroup member of the jahnsite group from the Hagendorf-Süd pegmatite, Oberpfalz, Bavaria, Germany. It was found in vugs in an altered feldspar area of a specimen composed predominantly of rockbridgeite, with hureaulite and relic triphylite. Other associated minerals in small vugs in the specimen were strengite and laueite. Whiteite-(CaMnFe) occurs as sprays and clusters of colourless to pale yellow, rod-like crystals, with diameters of typically 10 to 50 µm and lengths up to ∼ 500 µm. The crystals are flattened on {001} and elongated along [010]. The measured density is 2.80(2) g cm−3. Optically, whiteite-(CaMnFe) crystals are biaxial (+), with α=1.608(3), β=1.612(3), γ=1.624(3) and 2V(meas.) = 59(1)∘. The empirical formula from electron microprobe analyses and structure refinement is (Ca0.70Mn0.30)Mn(Fe1.232+Mn0.49Mg0.29Zn0.06)(Al1.88Fe0.123+)(PO4)3.96(OH)2(H2O)8. Whiteite-(CaMnFe) is monoclinic, P2 /a, a=14.925(5), b=7.0100(14), c=10.053(2) Å, β=111.31(2)∘, V=979.9(4) Å3 and Z=2. The crystal structure was refined using single-crystal data to wRobs=0.052 for 1613 reflections with I>3σ(I). Site occupancy refinements confirm the ordering of dominant Ca, Mn and Fe2+ in the X, M1 and M2 sites, respectively, of the general jahnsite-group formula XM1M22M32(H2O)8(OH)2(PO4)4.

A new mineral of the beryl group, johnkoivulaite, Cs(Be2B)Mg2Si6O18, was recovered from the gem gravels in the Pein Pyit area of the Mogok region in Myanmar. Thus far, only a single crystal has been identified. It has dimensions of about 5.8 × 5.7 × 5.5 mm. This specimen has an irregular shape but still has discernible crystal form with geometric growth patterns observed on the crystal faces. The crystal of johnkoivulaite is grayish-violet in color and strongly pleochroic, going from nearly colorless with E┴c to dark bluish-violet with E||c. Johnkoivulaite has a Mohs hardness of about 7½ and a measured density of 3.01(10) g/cm3. It is uniaxial (–) with ω = 1.607(1) and ε = 1.605(1) (white light). Electron microprobe analyses gave the empirical formula of (Cs0.85K0.10Na0.01)(Be1.88B1.12)(Mg1.66Fe0.27Mn0.01Al0.05) (Si5.98)O18 with Be calculated by stoichiometry and confirmed by LA-ICP-MS measurements. Johnkoivulaite is hexagonal, P6/mmc (no. 192) with a = 9.469(2), c = 9.033(2) Å, V = 701.5(3) Å3, and Z = 2. Johnkoivulaite is isostructural with beryl and exhibits partial substitution of B for Be at the distorted tetrahedral site, Mg for Al at the octahedral site, and Cs in the channel sites within the stacked Si6O18 rings. This substitution can be written as (CsMg2B)(☐Al2Be)–1. Johnkoivulaite, the seventh member of the beryl group, is named in honor of gemologist John Koivula in recognition of his contributions to mineralogy and gemology.

Whiteite-(MnMnMn), Mn2+Mn2+Mn2+2Al2(PO4)4(OH)2⋅8H2O, is a new whiteite-subgroup member of the jahnsite group from the Foote Lithium Company mine, Kings Mountain district, Cleveland County, North Carolina, USA. It was found in small vugs of partially oxidised pegmatite minerals on the East dump of the mine, in association with eosphorite, hureaulite, fairfieldite, mangangordonite, whiteite-(CaMnMn) and jasonsmithite. It occurs as sugary aggregates of blade-like crystals up to 0.1 mm long and as epitaxial overgrowths on whiteite-(CaMnMn). The crystals are colourless to very pale brown, with a vitreous lustre and a white streak. The blades are flattened on {001} and elongated along [010], with poor cleavage on {001}. The calculated density is 2.82 g⋅cm–3. Optically it is biaxial (–) with α = 1.599(2), β = 1.605(2), γ = 1.609(2) (white light); 2V (calc.) = 78.2°, having no observable dispersion or pleochroism, and with orientation X = b. Electron microprobe analyses and structure refinement gave the empirical formula (Mn2+0.59Ca0.38Na0.03)Σ1.00Mn1.00(Mn2+1.04Fe3+0.58Fe2+0.23Zn0.16Mg0.08)Σ2.09Al2.04(PO4)3.89(OH)3.18(H2O)7.26. Whiteite-(MnMnMn) is monoclinic, P2/a, a = 15.024(3) Å, b = 6.9470(14) Å, c = 9.999(2) Å, β = 110.71(3)°, V = 976.2(4) Å3 and Z = 2. The crystal structure was refined using synchrotron single-crystal data to wRobs = 0.057 for 2014 reflections with I > 3σ(I). Site occupancy refinements confirm the ordering of dominant Mn in the X, M1 and M2 sites of the general jahnsite-group formula XM1(M2)2(M3)2(H2O)8(OH)2(PO4)4. A review of published crystallochemical data for jahnsite-group minerals shows a consistent chemical pressure effect in these minerals, manifested as a contraction of the unit-cell parameter, a, as the mean size of the X and M1 site cations increases. This is analogous to negative thermal expansion, but with increasing cation size, rather than heating, inducing octahedral rotations that result in an anisotropic contraction of the unit cell.

Wildcatite (IMA2020–019) is a new calcium–iron(III) tellurate discovered at the Wildcat prospect in the Detroit district, Juab County, Utah. Wildcatite may take on a variety of appearances, ranging from transparent orange to brown coatings or masses to earthy, white polycrystalline coatings filling jasperoid fracture surfaces. Coatings of wildcatite are generally less than 0.1 mm thick and may cover up to 5 cm2, while nanoscale crystallites of wildcatite may form translucent red-brown “crystals” up to 0.1 mm. Wildcatite is found associated with gold, calcite, aragonite, native tellurium, manganese oxides, iron oxides, rare clinobisvanite, beyerite, coronadite, the Te oxides paratellurite and tellurite, and the Te oxysalts andymcdonaldite, burckhardtite, carlfriesite, eckhardite, frankhawthorneite, khinite, mcalpineite, tlapallite, and xocolatlite. The strongest powder diffraction lines are [dobsÅ(Iobs)(hkl)]: 3.33(100)(011), 2.60(55)(110), 2.30(59)(111), 2.05(33)(021), and 1.80(88)(112). The average size of wildcatite crystallites is 13 nm, thus the crystal structure of wildcatite was solved by Rietveld refinement, converging to a final RB value of 3.14%. The empirical formula of wildcatite, as determined by electron probe microanalysis and Rietveld refinement, is Ca0.98Bi3+0.02Pb0.01Fe3+0.73Mg0.05Mn2+0.02Zn0.01Cu0.00Te6+1.15Sb5+0.02Si0.01O5.44H0.56, simplified to the ideal formula of CaFe3+Te6+O5(OH). Wildcatite is trigonal, crystallizing in the space group P1m, with a = 5.2003(14) Å, c = 4.9669(14) Å, V = 116.3(1) Å3 and Z = 1. Wildcatite is structurally very similar to rosiaite (PbSb2O6), possessing a honeycomb-like two-dimensional framework of edge-sharing Fe3+O6 and Te6+O6 octahedra, sandwiching octahedrally coordinated Ca2+ cations. Minor OH substitution (∼10%) at the O sites is required for charge balance in wildcatite.

Mineral species that contain the decavanadate isopolyanion [V10O28]6–, including its protonated and mixed-valence variants, constitute the pascoite family of minerals. Within the pascoite family, the isostructural minerals pascoite and magnesiopascoite form the pascoite group and the isostructural minerals lasalite and ammoniolasalite form the lasalite group. Rakovanite, which was originally assigned the ideal formula Na3[H3V10O28]·15H2O, is redefined with the ideal formula (NH4)3Na3[V10O28]·12H2O.

Hydroxylpyromorphite, Pb5(PO4)3(OH), has been documented in the literature as a synthetic and naturally occurring phase for some time but has not previously been formally described as a mineral. It is fully described here for the first time using crystals collected underground in the Copps mine, Gogebic County, Michigan. Hydroxylpyromorphite occurs as aggregates of randomly oriented hexagonal prisms, primarily between about 20–35 μm in length and 6–10 μm in diameter. The mineral is colorless and translucent with vitreous luster and white streak. The Mohs hardness is ~3½–4; the tenacity is brittle, the fracture is irregular, and indistinct cleavage was observed on {001}. Electron microprobe analyses provided the empirical formula Pb4.97(PO4)3(OH0.69F0.33Cl0.06)Σ1.08. The calculated density using the measured composition is 7.32 g/cm3. Powder X-ray diffraction data for the type material is compared to data previously reported for hydroxylpyromorphite from the talc mine at Rabenwald, Austria, and from Whytes Cleuch, Wanlockhead, Scotland. Hydroxylpyromorphite is hexagonal, P63/m, at 100 K, a = 9.7872(14), c = 7.3070(10) Å, V = 606.16(19) Å3, and Z = 2. The structure [R1 = 0.0181 for 494 F>4σ(F) reflections] reveals that hydroxylpyromorphite adopts a column anion arrangement distinct from other members of the apatite supergroup due to the presence of fluorine and steric constraints imposed by stereoactive lone-pair electrons of Pb2+ cations. The F– anion sites are displaced slightly from hydroxyl oxygen anions, which allows for stronger hydrogen-bonding interactions that may in turn stabilize the observed column-anion arrangement and overall structure. Our modern characterization of hydroxylpyromorphite provides deeper understanding to a mineral useful for remediation of lead-contaminated water.

The new minerals allantoin (IMA2020–004a), C4H6N4O3, and natrosulfatourea (IMA2019–134), Na2(SO4)[CO(NH2)2], were found in the Rowley mine, Maricopa County, Arizona, USA, where they occur together in bat guano in association with aphthitalite and urea. Allantoin properties: colorless, transparent, untwinned blades to 0.3 mm; white streak; vitreous luster; brittle; Mohs hardness 1½; conchoidal fracture; good {100} cleavage; 1.72(2) g/cm3 density; biaxial (+) with α = 1.558(2), β = 1.593(2), γ = 1.715(3); 2V = 60(1)°; slight r > v dispersion; optical orientation: Y = b, Z ^ a = 30° in obtuse β. Natrosulfatourea properties: colorless, transparent, untwinned prisms to 0.3 mm; white streak; vitreous luster; brittle; Mohs hardness 1½; irregular fracture; perfect {100} cleavage; 1.97(2) g/cm3 density; biaxial (+) with α = 1.456(2), β = 1.464(5), γ = 1.524(2); 2V = 42(1)°; no dispersion; optical orientation: X = a, Y = c, Z = b. Quantitative chemical analyses could not be obtained for allantoin. Electron microprobe analyses provided the empirical formula Na2.02(S0.98O4)[CO(NH2)2] for natrosulfatourea. Allantoin is monoclinic, P21/c, a = 8.0304(9), b = 5.1596(5), c = 14.8011(18) Å, β = 93.017(7)°, V = 612.41(11) Å3, and Z = 4. Natrosufatourea is orthorhombic, Pbcn, a = 5.5918(4), b = 18.1814(14), c = 6.7179(5) Å, V = 682.98(9) Å3, and Z = 4. The crystal structure of allantoin (R1 = 0.0432 for 1073 I > 2σI) is the same as that reported for the equivalent organic compound. In the structure of natrosulfatourea (R1 = 0.0413 for 785 I > 2σI) NaO6 polyhedra and SO4 tetrahedra form polyhedral layers. The O atom of the CO(NH2)2 (urea) group ligates to two Na atoms and projects into the space between polyhedral layers, linking adjacent layers through hydrogen bonds.

Thebaite-(NH4), (NH4,K)3Al(C2O4)(PO3OH)2(H2O), is a new mineral species (IMA2020-072) from the Rowley mine, Maricopa County, Arizona, USA. It occurs in an unusual bat-guano-related, post-mining assemblage of phases that include a variety of vanadates, phosphates, oxalates and chlorides, some containing NH4+. Other secondary minerals found in association with thebaite-(NH4) are antipinite, vanadinite and at least one other new mineral. Crystals of thebaite-(NH4) are colourless blades up to ~0.1 mm in length. The streak is white, lustre is vitreous, Mohs hardness is 1½–2, tenacity is brittle and fracture is splintery. There are two good cleavages in the [010] zone, probably {100} and {10$\bar{2}$}. The calculated density is 2.093 g⋅cm–3. Thebaite-(NH4) is optically biaxial (–) with α = 1.490(2), β = 1.534(2), γ = 1.570(2) (white light); 2V = 82.7(5)°; slight r > v dispersion; and orientation X = b, Y ^ c = 13° in obtuse β. Electron microprobe analysis gave the empirical formula [(NH4)2.12K0.69Na0.20]Σ3.01(Al0.84Fe3+0.11V3+0.04)Σ0.99(C2O4)[(P0.98Si0.02)O3OH]2(H2O), with the C, N and H contents constrained by the crystal structure. Raman spectroscopy confirmed the presence of NH4 and C2O4. Thebaite-(NH4) is monoclinic, P21/c, with a = 11.156(9), b = 6.234(6), c = 18.651(16) Å, β = 102.928(15)°, V = 1264.2(19) Å3 and Z = 4. The structural unit in the crystal structure of thebaite-(NH4) (R1 = 0.0612 for 863 Io > 2σI reflections) is a double-strand chain of corner-sharing AlO6 octahedra and PO3OH tetrahedra decorated by additional PO3OH tetrahedra and C2O4 groups. The decorated chains connect to one another through bonds to NH4+ and K+ and through hydrogen bonds.

The wallpaper-type crystal structure of wightmanite, Mg5(BO3)O(OH)5·1–2H2O, has been reanalyzed in order to better understand the position and bonding of hydrogen atoms. Single-crystal structure refinement yielded the monoclinic I2/m unit cell a = 13.5165(18), b = 3.0981(3), c = 18.170(3)Å, ß = 91.441(6)°, and V = 760.65(17)Å3, Z = 4. Hydrogen atoms of OH groups pointing to the inside of the elliptical channels oriented parallel to [010] are arranged in the form of two overlying, a–c parallel planar pentagons. The two pentagons point in opposite directions. Hydrogen-bond analysis shows that the hydroxyl groups are linked by complex polyfurcated, intra-molecular hydrogen bonds forming a web-like network coating the walls of the channels. The longest distance between hydrogens (7.226 Å) is observed in the pentagonal planes of the channel. The anisotropically refined oxygen atoms of the zeolitic water show their strongest vibration parallel to the b axis and in the direction of the largest diameter of the elliptical channel and similarly form a complex inter-molecular hydrogen-bond system to the hydroxyl groups coating the channel walls. This complex bonding is expressed in the Raman spectrum by a broad band between 3100 and 3300 cm–1 that is assigned to the OH / H2O stretching mode and one strong band at 3661 cm–1 attributable to an OH-stretching mode. Infrared spectra also show a pronounced broad band between 3200 and 3700 cm–1 attributed to H2O and OH-stretching modes. The weak bands around 1600 cm–1 observed in the Raman and IR spectra are probably due to relatively weakly bound water in the channels.

Jasonsmithite (IMA2019-121), Mn42+ZnAl(PO4)4(OH)(H2O)7·3.5H2O, is a pegmatite-phosphate mineral from the Foote Lithium Company mine, Kings Mountain district, Cleveland County, North Carolina, U.S.A. It is interpreted as having formed by late-stage, low-temperature hydrothermal alteration. Crystals are colorless to light brown, slightly flattened prisms to about 1 mm in length with wedge-shaped terminations. The mineral is transparent with vitreous luster, white streak, Mohs hardness 2, brittle tenacity, irregular fracture, and perfect {001} cleavage. The density is 2.63(2) g/cm3. Jasonsmithite is biaxial (–), with α = 1.561(2), β = 1.580(2), γ = 1.581(2), measured in white light. The 2V is 25(5)° and dispersion is r < ν moderate. The optical orientation is Y = b, X ^ c = 18° in obtuse β. The Raman spectrum is dominated by vibrational modes of PO4 and ZnO4 tetrahedra, AlO6 and MnO6 octahedra, and OH groups. Electron microprobe analyses gave the empirical formula (Mn3.09Fe0.87)Σ3.96Zn1.05Al0.98(PO4)4(OH)(H2O)7·3.5H2O. The mineral is monoclinic, P21/c, a = 8.5822(3), b = 13.1770(6), c = 20.3040(14) Å, β = 98.485(7)°, V = 2271.0(2) Å3, and Z = 4. The structure (R1 = 0.0443 for 3685 I>2σI reflections) contains zigzag chains of edge-sharing MnO6 octahedra that corner-link to adjacent chains and to PO4 tetrahedra to form sheets, which are decorated by ZnO4 tetrahedra. The sheets are linked to one another via dimers of AlO6 octahedra, forming a framework with large channels containing H2O groups. With H2O groups removed, the framework has a void space of 70.2% per unit cell, and a framework density of 14.5 polyhedral atoms/1000 Å3, which would place jasonsmithite among the most porous minerals.

Native tungsten (IMA2011-004), W, is officially described as a new mineral from gold placers in the Bol'shaya Pol'ya river valley, Prepolar Urals, Russia, associated with yttriaite-(Y) and from quartz veins in the Mt Neroyka rock-crystal field, Ust–Puiva, Tyumenskaya Oblast', Russia. Tungsten forms polycrystalline grains and masses, and rarely cubo-octahedra. It is silver white to steel grey in colour, with metallic lustre and grey streak. The calculated density is 19.226 g/cm3. The Vickers hardness (VHN25) is 571.45 kg/mm2. In plane polarised light, tungsten is white with a pale-yellow tint and optically isotropic. Electron microprobe analyses of Bol'shaya Pol'ya river valley material provided W 99.27, Mo 0.06, Mn 0.04, Fe 0.01, total 99.38 wt.%. The five strongest powder X-ray diffraction lines are [dobs Å(I)(hkl)]: 2.2422(100)(110), 1.5835(25)(200), 1.2929(48)(211), 1.0010(23)(310) and 0.8457(24)(321). Tungsten is cubic, Im$\bar{3}$m, a = 3.1648(4) Å, V = 31.69(4) Å3 and Z = 2. Some additional occurrences of native tungsten and technogenic tungsten found in Nature are also described.

Seaborgite (IMA2019-087), LiNa6K2(UO2)(SO4)5(SO3OH)(H2O), is a new mineral species from the Blue Lizard mine, Red Canyon, San Juan County, Utah, U.S.A. It is a secondary phase found on gypsum in association with copiapite, ferrinatrite, ivsite, metavoltine, and römerite. Seaborgite occurs in sprays of light-yellow, long flattened prisms or blades, up to about 0.2 mm in length. Crystals are elongated on [100], flattened on {010}, and exhibit the forms {100}, {010}, {001}, and {101}. The mineral is transparent with vitreous luster and very pale-yellow streak. It exhibits bright lime-green fluorescence under a 405 nm laser. The Mohs hardness is ~2½. The mineral has brittle tenacity, curved or conchoidal fracture, and one good cleavage on {100}. The measured density is 2.97(2) g/cm3. The mineral is immediately soluble in H2O at room temperature. The mineral is optically biaxial (–), α = 1.505(2), β = 1.522(2), γ = 1.536(2) (white light); 2Vmeas = 85(1)°; moderate r < ν dispersion; orientation X ^ a ≈ 10°; pleochroic X colorless, Y and Z light green-yellow; X < Y ≈ Z. EPMA and LA-ICP-MS analyses of seaborgite undermeasured its Li, K, and Na. The empirical formula using Li, Na, and K based on the structure refinement is Li1.00Na5.81K2.19(UO2)(SO4)5(SO3OH)(H2O). Seaborgite is triclinic, P1, a = 5.4511(4), b = 14.4870(12), c = 15.8735(15) Å, α = 76.295(5), β = 81.439(6), γ = 85.511(6)°, V = 1203.07(18) Å3, and Z = 2. The structure (R1 = 0.0377 for 1935 I = 2σI) contains [(UO2)2(SO4)8]4– uranyl-sulfate clusters that are linked into a band by bridging LiO4 tetrahedra. The bands are linked through peripheral SO4 tetrahedra forming a thick heteropolyhedral layer. Channels within the layers contain a K site, while an additional K site, six Na sites, and an SO3OH group occupy the space between the heteropolyhedral layers.

Galeaclolusite, [Al6(AsO4)3(OH)9(H2O)4]⋅8H2O, is a new secondary hydrated aluminium arsenate mineral from Cap Garonne, Var, France. It forms crusts and spheroids of white fibres up to 50 μm long by 0.4 μm wide and only 0.1 μm thick. The fibres are elongated along [001] and flattened on (100). The calculated density is 2.27 g⋅cm–3. Optically, galeaclolusite is biaxial with α = 1.550(5), β not determined, γ = 1.570(5) (white light) and partial orientation: Z = c (fibre axis). Electron microprobe analyses coupled with crystal structure refinement results gives an empirical formula based on 33 O atoms of Al5.72Si0.08As2.88O33H34.12. Galeaclolusite is orthorhombic, Pnma, with a = 19.855(4), b = 17.6933(11), c = 7.7799(5) Å, V = 2733.0(7) Å3 and Z = 4. The crystal structure of galeaclolusite was established from its close relationship to bulachite and refined using synchrotron powder X-ray diffraction data. It is based on heteropolyhedral layers, parallel to (100), of composition Al6(AsO4)3(OH)9(H2O)4 and with H-bonded H2O between the layers. The layers contain [001] spiral chains of edge-shared octahedra, decorated with corner-connected AsO4 tetrahedra, that are the same as in the mineral liskeardite.

Jeankempite, Ca5(AsO4)2(AsO3OH)2(H2O)7, is a new mineral species (IMA2018-090) discovered amongst coatings of arsenate minerals on oxidised copper arsenides from the Mohawk No. 2 mine, Mohawk, Keweenaw County, Michigan, USA. The new mineral occurs as lamellar bundles of colourless to white plates up to 1 mm wide and is visually indistinguishable from guérinite, with which it forms intergrowths. Jeankempite is transparent to translucent with a waxy lustre and white streak, is non-fluorescent under longwave and shortwave ultraviolet illumination, has a Mohs hardness of ~1.5 and brittle tenacity with uneven fracture. Crystals are flattened on {01$\bar{1}$} and exhibit perfect cleavage on {01$\bar{1}$}. Optically, jeankempite is biaxial (+), α = 1.601(2), β = 1.607(2), γ = 1.619(2) (white light); 2Vmeas.= 72(2)° and 2Vcalc.= 71.0°. The empirical formula is (Ca4.97Na0.013Mg0.017)(As3.99S0.01)4O23H16, based on 23 O and 16 H atoms per formula unit. Thermogravimetric analysis indicates that jeankempite undergoes four weight losses totalling 16.82%, close to the expected loss of 16.30%, corresponding to eight H2O. Jeankempite is triclinic,P$\bar{1}$,a= 6.710(6),b= 14.901(14),c= 15.940(15) Å, α = 73.583(12)°, β = 81.984(12)°, γ=82.754(12)°,V= 1507(2) Å3andZ= 3. The final structure was refined toR1= 0.0591 for 2781 reflections withIobs> 3σI. The crystal structure of jeankempite is built from a network of edge- and vertex-sharing CaO6, CaO7and AsO4polyhedra, and we hypothesise that the new mineral has formed due to a topotactic reaction brought on by dehydration of preexisting guérinite.

Monteneroite (IMA2020-028), Cu2+Mn2+2(AsO4)2⋅8H2O, is a new vivianite-structure mineral from the Monte Nero mine, Rocchetta di Vara, La Spezia, Liguria, Italy. It is a secondary mineral that crystallised from As-, Cu- and Mn-rich fluids and it is associated with braunite, copper, cuprite, rhodochrosite and strashimirite. Monteneroite occurs as light green, thick blades up to ~2.5 mm long. The streak is white. Crystals are transparent with vitreous lustre. The mineral has Mohs hardness of 2, is somewhat sectile, exhibits two cleavages ({010} perfect and {001} fair) and has irregular stepped fracture. The measured density is 2.97(2) g cm–3. Monteneroite is optically biaxial (+), with α = 1.604(2), β = 1.637(2) and γ = 1.688(2), determined in white light; 2V = 80(1)°; slight dispersion is r < v, orientation: X = b; Z ^ c = 52° in obtuse β. Electron microprobe analyses provided the empirical formula (Cu2+0.88Mn2+0.11)Σ0.99Mn2+2.00(As1.00O4)2⋅8H2O. Monteneroite is monoclinic, C2/m, a = 10.3673(14), b = 13.713(2), c = 4.8420(8) Å, β = 105.992(8)°, V = 661.72(18) Å3 and Z = 2. Monteneroite has a vivianite-type structure (R1 = 0.0535 for 534 I > 2σI reflections). It is the first mineral with this structure type to be defined with ordered octahedral cation sites.