Monteneroite, Cu2+Mn2+2(AsO4)2⋅8H2O, a new vivianite-structure mineral with ordered cations from the Monte Nero mine, Liguria, Italy

2020 ◽  
pp. 1-7
Author(s):  
Anthony R. Kampf ◽  
Jakub Plášil ◽  
Barbara P. Nash ◽  
Marco E. Ciriotti ◽  
Fabrizio Castellaro ◽  
...  
Keyword(s):  
White Light ◽  
Electron Microprobe ◽  
Empirical Formula ◽  
Structure Type ◽  
Secondary Mineral ◽  
Octahedral Cation ◽  
Mohs Hardness ◽  
Cation Sites ◽  
Light Green ◽  
Measured Density

Abstract 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.

Kapellasite, Cu3Zn(OH)6CI2, a new mineral from Lavrion, Greece, and its crystal structure

2006 ◽  
Vol 70 (3) ◽  
pp. 329-340 ◽  
Author(s):  
W. Krause ◽  
H.-J. Bernhardt ◽  
R.S.W. Braithwaite ◽  
U. Kolitsch ◽  
R. Pritchard
Keyword(s):  
Crystal Structure ◽  
Electron Microprobe ◽  
Empirical Formula ◽  
New Mineral ◽  
Crystal Data ◽  
Secondary Mineral ◽  
Unit Cell Parameters ◽  
Cell Parameters ◽  
Pale Green ◽  
Light Green

AbstractKapellasite, Cu3Zn(OH)6Cl2, is a new secondary mineral from the Sounion No. 19 mine, Kamariza, Lavrion, Greece. It is a polymorph of herbertsmithite. Kapellasite forms crusts and small aggregates up to 0.5 mm, composed of bladed or needle-like indistinct crystals up to 0.2 mm long. The colour is green-blue, the streak is light green-blue. There is a good cleavage parallel to ﹛0001﹜. Kapellasite is uniaxial negative, ω = 1.80(1), ε = 1.76(1); pleochroism is distinct, with E = pale green, O = green-blue. Dmeas = 3.55(10) g/cm3; Dcalc. = 3.62 g/cm3. Electron microprobe analyses of the type material gave CuO 58.86, ZnO 13.92, NiO 0.03, CoO 0.03, Fe2O3 0.04, Cl 16.70, H2O (calc.) 12.22, total 101.80, less O = Cl 3.77, total 98.03 wt.%. The empirical formula is (Cu3.24Zn0.75)Σ3.99(OH)5.94Cl2.06, based on 8 anions. The five strongest XRD lines are [d in Å (I/I0, hkl)] 5.730 (100, 001), 2.865 (11, 002), 2.730 (4, 200), 2.464 (9, 021/201), 1.976 (5, 022/202). Kapellasite is trigonal, space group Pml, unit-cell parameters (from single-crystal data) a = 6.300(1), c = 5.733(1) Å, V= 197.06(6) Å3, Z = 1. The crystal structure of kapellasite is based on brucite-like sheets parallel to (0001), built from edge-sharing distorted M(OH,Cl)6 (M = Cu, Zn) octahedra. The sheets stack directly on each other (…AAA… stacking). Bonding between adjacent sheets is only due to weak hydrogen and O…C1 bonds. The name is in honour of Christo Kapellas (1938–2004), collector and mineral dealer from Kamariza, Lavrion, Greece.

Mauriziodiniite, NH4(As2O3)2I, the ammonium and iodine analogue of lucabindiite from the Torrecillas mine, Iquique Province, Chile

2019 ◽  
Vol 84 (2) ◽  
pp. 267-273
Author(s):  
Anthony R. Kampf ◽  
Barbara P. Nash ◽  
Arturo A. Molina Donoso
Keyword(s):  
White Light ◽  
Electron Microprobe ◽  
Empirical Formula ◽  
New Mineral ◽  
Calculated Density ◽  
Secondary Alteration ◽  
Layer Sequence ◽  
Mohs Hardness ◽  
Elastic Fracture ◽  
White Streak

AbstractThe new mineral mauriziodiniite (IMA2019-036), NH4(As2O3)2I, was found at the Torrecillas mine, Iquique Province, Chile, where it is a secondary alteration phase associated with calcite, cuatrocapaite-(NH4), lavendulan, magnesiokoritnigite and torrecillasite on matrix consisting of native arsenic, arsenolite and pyrite. Mauriziodiniite occurs as hexagonal tablets up to ~300 μm in diameter. Crystals are colourless and transparent, with pearly to adamantine lustre and white streak. The Mohs hardness is ~1. Tablets are sectile and easily flexible, but not elastic. Fracture is curved, irregular and stepped. Cleavage is perfect on {001}. The calculated density is 3.916 g/cm3. Optically, mauriziodiniite is uniaxial (–) with ω = 2.07(calc) and ɛ = 1.770(5) (white light). The empirical formula, determined from electron microprobe analyses, is (NH4)0.94K0.03(As2O3)2I0.92Cl0.03. Mauriziodiniite is hexagonal, P6/mmm, a = 5.289(2), c = 9.317(2) Å, V = 225.68(18) Å3 and Z = 1. The structure, refined to R1 = 4.16% for 135 Io > 2σI reflections, contains three types of layers: (1) a planar neutral As2O3 (arsenite) sheet; (2) an NH4+ layer that links adjacent arsenite sheets via bonds to their O atoms; and (3) an I– layer that links adjacent arsenite sheets via bonds to their As atoms. The layer sequence is I–As2O3–NH4–As2O3–I. Mauriziodiniite is isostructural with lucabindiite and is structurally related to gajardoite, cuatrocapaite-(NH4), cuatrocapaite-(K) and torrecillasite.

Smamite, Ca2Sb(OH)4[H(AsO4)2]·6H2O, a new mineral and a possible sink for Sb during weathering of fahlore

2020 ◽  
Vol 105 (4) ◽  
pp. 555-560
Author(s):  
Jakub Plášil ◽  
Anthony R. Kampf ◽  
Nicolas Meisser ◽  
Cédric Lheur ◽  
Thierry Brunsperger ◽  
...  
Keyword(s):  
White Light ◽  
Electron Microprobe ◽  
Room Temperature ◽  
New Mineral ◽  
Calculated Density ◽  
New Mineral Species ◽  
Mohs Hardness ◽  
Measured Density ◽  
Ore District ◽  
The Ideal

Abstract Smamite, Ca2Sb(OH)4[H(AsO4)2]·6H2O, is a new mineral species from the Giftgrube mine, Rauenthal, Sainte-Marie-Aux-Mines ore-district, Haut-Rhin department, France. It is a supergene mineral found in quartz-carbonate gangue with disseminated to massive tennantite-tetrahedrite series minerals, native arsenic, Ni-Co arsenides, and supergene minerals picropharmacolite, fluckite, and pharmacolite. Smamite occurs as lenticular crystals growing in aggregates up to 0.5 mm across. The new mineral is whitish to colorless, transparent with vitreous luster and white streak; non-fluorescent under UV radiation. The Mohs hardness iŝ3½; the tenacity is brittle, the fracture is curved, and there is no apparent cleavage. The measured density is 2.72(3) g/cm3; the calculated density is 2.709 g/cm3 for the ideal formula. The mineral is insoluble in H2O and quickly soluble in dilute (10%) HCl at room temperature. Optically, smamite is biaxial (–), α = 1.556(1), β = 1.581(1), γ = 1.588(1) (white light). The 2V (meas) = 54(1)°; 2V (calc) = 55.1°. The dispersion is weak, r &gt; ν. Smamite is non-pleochroic. Electron microprobe analyses provided the empirical formula Ca2.03Sb0.97(OH)4[H1.10(As1.99Si0.01O4)2]·6H2O. Smamite is triclinic, P1–, a = 5.8207(4), b = 8.0959(6), c = 8.21296(6) Å, α = 95.8343(7)°, β = 110.762(8)°, γ = 104.012(7)°, V = 402.57(5) Å3, and Z = 1. The structure (Robs = 0.027 for 1518 I&gt;3σI reflections) is based upon {Ca2(H2O)6Sb(OH)4[H(AsO4)2]} infinite chains consisting of edge-sharing dimers of Ca(H2O)3O2(OH)2 polyhedra that share edges with Sb(OH)4O2 octahedra; adjacent chains are linked by H-bonds, including one strong, symmetrical H-bond with an O–H bond-length of ∼1.23 Å. The name “smamite” is based on the acronym of the Sainte-Marie-aux-Mines district.

scholarly journals Chirvinskyite, (Na,Ca)13(Fe,Mn,□)2(Ti,Nb)2(Zr,Ti)3-(Si2O7)4(OH,O,F)12, a New Mineral with a Modular Wallpaper Structure, from the Khibiny Alkaline Massif (Kola Peninsula, Russia)

Minerals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 219
Author(s):  
Victor Yakovenchuk ◽  
Yakov Pakhomovsky ◽  
Taras Panikorovskii ◽  
Andrey Zolotarev ◽  
Julia Mikhailova ◽  
...  
Keyword(s):  
Kola Peninsula ◽  
Empirical Formula ◽  
Inorganic Compounds ◽  
Structure Type ◽  
New Mineral ◽  
State University ◽  
Mohs Hardness ◽  
Alkaline Massif ◽  
Khibiny Alkaline Massif ◽  
White Streak

Chirvinskyite, (Na,Ca)13(Fe,Mn,□)2(Ti,Nb)2(Zr,Ti)3(Si2O7)4(OH,O,F)12, is a new wöhlerite–related zirconotitano–sorosilicate. It is triclinic, P1, a = 7.0477(5), b = 9.8725(5), c = 12.2204(9) Å, α = 77.995(5), β = 82.057(6), γ = 89.988(5)°, V = 823.35(9) Å3, Z = 1. The mineral was found in albitized alkaline pegmatites in a foyaite of the Mt. Takhtarvumchorr (Khibiny alkaline massif, Kola Peninsula, Russia, N 67°40’, E 33°33’). Chirvinskyite forms sheaf–like and radiated aggregates (up to 6 mm in diameter) of split fibrous crystals hosted by saccharoidal fluorapatite and albite. The mineral is pale cream in color, with a silky luster and a white streak. The cleavage is not recognized. Mohs hardness is 5. Chirvinskyite is biaxial (–), α 1.670(2), β 1.690(2), γ 1.705(2) (589 nm), 2Vcalc = 80.9°. The calculated and measured densities are 3.41 and 3.07(2) g·cm−3, respectively. The empirical formula based on Si = 8 apfu is (Na9.81Ca3.28K0.01)∑13.10(Fe0.72Mn0.69□0.54Mg0.05)∑2.00 (Ti1.81Nb0.19)∑2.00(Zr2.27Ti0.63)∑2.90(Si2O7)4{(OH)5.94O3.09F2.97}∑12.00. Chirvinskyite belongs to a new structure type of minerals and inorganic compounds and is related to the wöhlerite-group minerals. Its modular “wallpaper” structure consists of disilicate groups Si2O7 and three types of “octahedral walls”. The mineral is named in honor of Petr Nikolaevich Chirvinsky (1880–1955), Russian geologist and petrographer, head of the Petrography Department of the Perm’ State University (1943–1953), for his contributions to mineralogy and petrology, including studies of the Khibiny alkaline massif.

Natromarkeyite and pseudomarkeyite, two new calcium uranyl carbonate minerals from the Markey mine, San Juan County, Utah, USA

2020 ◽  
Vol 84 (5) ◽  
pp. 753-765 ◽  
Author(s):  
Anthony R. Kampf ◽  
Travis A. Olds ◽  
Jakub Plášil ◽  
Peter C. Burns ◽  
Joe Marty
Keyword(s):  
Electron Microprobe ◽  
San Juan ◽  
Secondary Phases ◽  
Yellow Colour ◽  
Uranyl Carbonate ◽  
Mohs Hardness ◽  
San Juan County ◽  
Pale Green ◽  
Light Green ◽  
White Streak

AbstractThe new minerals natromarkeyite, Na2Ca8(UO2)4(CO3)13(H2O)24⋅3H2O (IMA2018-152) and pseudomarkeyite, Ca8(UO2)4(CO3)12(H2O)18⋅3H2O (IMA2018-114) were found in the Markey mine, San Juan County, Utah, USA, where they occur as secondary phases on asphaltum. Natromarkeyite properties are: untwinned blades and tablets to 0.2 mm, pale yellow green colour; transparent; white streak; bright bluish white fluorescence (405 nm laser); vitreous to pearly lustre; brittle; Mohs hardness 1½ to 2; irregular fracture; three cleavages ({001} perfect, {100} and {010} good); density = 2.70(2) g cm–3; biaxial (–) with α = 1.528(2), β = 1.532(2) and γ = 1.533(2); and pleochroism is X = pale green yellow, Y ≈ Z = light green yellow. Pseudomarkeyite properties are: twinned tapering blades and tablets to 1 mm; pale green yellow colour; transparent; white streak; bright bluish white fluorescence (405 nm laser); vitreous to pearly lustre; brittle; Mohs hardness ≈ 1; stepped fracture; three cleavages ({10$\bar{1}$} very easy, {010} good, {100} fair); density = 2.88(2) g cm–3; biaxial (–) with α = 1.549(2), β = 1.553(2) and γ = 1.557(2); and it is nonpleochroic. The Raman spectra of markeyite, natromarkeyite and pseudomarkeyite are very similar and exhibit bands consistent with UO22+, CO32– and O–H. Electron microprobe analyses provided the empirical formula Na2.01Ca7.97Mg0.03Cu2+0.05(UO2)4(CO3)13(H2O)24⋅3H2O (–0.11 H) for natromarkeyite and Ca7.95(UO2)4(CO3)12(H2O)18⋅3H2O (+0.10 H) for pseudomarkeyite. Natromarkeyite is orthorhombic, Pmmn, a = 17.8820(13), b = 18.3030(4), c = 10.2249(3) Å, V = 3336.6(3) Å3 and Z = 2. Pseudomarkeyite is monoclinic, P21/m, a = 17.531(3), b = 18.555(3), c = 9.130(3) Å, β = 103.95(3)°, V = 2882.3(13) Å3 and Z = 2. The structures of natromarkeyite (R1 = 0.0202 for 2898 I > 2σI) and pseudomarkeyite (R1 = 0.0787 for 2106 I > 2σI) contain uranyl tricarbonate clusters that are linked by (Ca/Na)–O polyhedra forming thick corrugated heteropolyhedral layers. Natromarkeyite is isostructural with markeyite; pseudomarkeyite has a very similar structure.

Cuatrocapaite-(NH4) and cuatrocapaite-(K), two new minerals from the Torrecillas mine, Iquique Province, Chile, related to lucabindiite and gajardoite

2019 ◽  
Vol 83 (5) ◽  
pp. 741-748 ◽  
Author(s):  
Anthony R. Kampf ◽  
Nikita V. Chukanov ◽  
Gerhard Möhn ◽  
Maurizio Dini ◽  
Arturo A. Molina Donoso ◽  
...  
Keyword(s):  
General Formula ◽  
White Light ◽  
Electron Microprobe ◽  
Dominant Species ◽  
Empirical Formulas ◽  
Secondary Alteration ◽  
Cell Parameters ◽  
Layer Sequence ◽  
Mohs Hardness

AbstractThe new minerals cuatrocapaite-(NH4) (IMA2018-083) and cuatrocapaite-(K) (IMA2018-084) are the NH4- and K-dominant members of a series with the general formula (NH4,K)3(NaMg□)(As2O3)6Cl6·16H2O. Both minerals were found at the Torrecillas mine, Iquique Province, Chile, where they occur as secondary alteration phases. Both minerals occur as hexagonal tablets up to ~0.3 mm in diameter. They are transparent, with a vitreous lustre and white streak. For both, the Mohs hardness isca. 2½, the crystals are somewhat flexible, but not elastic, the fracture is irregular and the cleavage is perfect on {001}. The measured densities are 2.65(2) and 2.76(2) g/cm3for the NH4- and K-dominant species, respectively. Optically, cuatrocapaite-(NH4) is uniaxial (–) with ω = 1.779(3) andε= 1.541(3) and cuatrocapaite-(K) is uniaxial (–) with ω = 1.777(3) andε= 1.539(3) (white light). The minerals are insoluble in acids, but decompose in NaOH(aq). The empirical formulas, determined from electron-microprobe analyses, are (NH4)2.48Na1.66Mg0.87K0.09(As12O18.05)Cl5.88·16.02H2O and K2.68Na1.33Mg0.93(NH4)0.31(As12O18.01)Cl6.16·16.04H2O. The minerals are trigonal, space groupR${\bar 3}$m; the cuatrocapaite-(NH4) cell parameters area= 5.25321(19),c= 46.6882(19) Å,V= 1115.80(9) Å3andZ= 1; the cuatrocapaite-(K) cell parameters area= 5.2637(15),c= 46.228(8) Å,V= 1109.2(7) Å3andZ= 1. The structures, refined for cuatrocapaite-(NH4) toR1= 1.78% for 544Io> 2σIreflections, contain four types of layers: (1) a planar neutral As2O3(arsenite) sheet; (2) an (${\rm NH}_{\rm 4}^{\vskip -2pt\rm \scale65% +} $,K+) layer that links adjacent arsenite sheets; (3) a Cl–layer placed on the As side of each arsenite; and (4) a layer containing partially occupied Na, Mg and H2O sites that is flanked on either side by Cl layers. The layer sequence for the type 1, 2 and 3 layers is identical to the Cl–As2O3–K–As2O3–Cl layer sequence in the structures of lucabindiite and gajardoite.

Natropharmacoalumite, NaAl4[(OH)4(AsO4)3].4H2O, a new mineral of the pharmacosiderite supergroup and the renaming of aluminopharmacosiderite to pharmacoalumite

2010 ◽  
Vol 74 (5) ◽  
pp. 929-936 ◽  
Author(s):  
M. S. Rumsey ◽  
S. J. Mills ◽  
J. Spratt
Keyword(s):  
Empirical Formula ◽  
Direct Methods ◽  
Structure Type ◽  
New Mineral ◽  
Gold Mine ◽  
Nomenclature System ◽  
Cubic Crystals ◽  
X Ray ◽  
Mohs Hardness ◽  
Dominant Cation

AbstractNatropharmacoalumite, ideally NaAl4[(OH)4(AsO4)3]·4H2O, is a new mineral from the Maria Josefa Gold mine, Rodalquilar, Andalusia region, Spain. It occurs as colourless, intergrown cubic crystals with chenevixite, kaolinite, jarosite and indeterminable mixtures of Fe and Sb oxyhydroxides. Individual crystals are up to 0.5 mm on edge, although crystals are more commonly ˜0.25 mm across and occur in patchy aggregates several millimetres across. The mineral is transparent with a vitreous to adamantine lustre. It is brittle with an imperfect cleavage, irregular fracture and a white streak. The Mohs hardness is ˜2.5 with a calculated densityof 2.56 g cm–3 for the empirical formula. Electron microprobe analyses yielded Na2O 2.52%, K2O 1.49%, Al2O3 29.50%, As2O5 48.84% and H2O was calculated in line with the structural analysis as 16.28% totalling 98.63%. The empirical formula, based upon 20.21 oxygen atoms, is [Na0.57K0.22(H3O)0.21]Σ1.00Al4.05(As2.97O12)(OH)4·4H2O. The five strongest lines in the X-ray powder diffraction pattern are [dobs(Å), Iobs,(hkl)]: 7.759,100,(100); 4.473,40,(111); 3.870,50,(200); 2.446,9,(301); 2.331,12,(311). Natropharmacoalumite is cubic, space group with a = 7.7280(3) Å, V = 461.53(3) Å3 and Z = 1. The crystal structure was solved by direct methods and refined to R1 = 0.063 for 295 reflections with F>4σ(F). The structure conforms broadly to that of the general pharmacosiderite structure type, with Na as the dominant cation in cavities of strongly distorted Al octahedra and As tetrahedra. A new group nomenclature system for minerals with the pharmacosiderite structure has been established, including the renaming of aluminopharmacosiderite to pharmacoalumite.

Ferribushmakinite, Pb2Fe3+(PO4)(VO4)(OH), the Fe3+ analogue of bushmakinite from the Silver Coin mine, Valmy, Nevada

2015 ◽  
Vol 79 (3) ◽  
pp. 661-669 ◽  
Author(s):  
A. R. Kampf ◽  
P. M. Adams ◽  
B. P. Nash ◽  
J. Marty
Keyword(s):  
Low Temperature ◽  
Electron Microprobe ◽  
New Mineral ◽  
Secondary Mineral ◽  
X Ray Diffraction ◽  
Calculated Density ◽  
X Ray ◽  
Silver Coin ◽  
Humboldt County ◽  
Mohs Hardness

AbstractFerribushmakinite (IMA2014-055), Pb2Fe3+(PO4)(VO4)(OH), the Fe3+ analogue of bushmakinite, is a new mineral from the Silver Coin mine, Valmy, Iron Point district, Humboldt County, Nevada, USA, where it occurs as a low-temperature secondary mineral in association with plumbogummite, mottramite, Br-rich chlorargyrite and baryte on massive quartz. Ferribushmakinite forms yellow slightly flattened prisms up to 0.2 mm long growing in X and sixling twins. The streak is pale yellow. Crystals are translucent and have adamantine lustre. The Mohs hardness is ∼2, the tenacity is brittle, the fracture is irregular to splintery and crystals exhibit one or two fair cleavages in the [010] zone. The calculated density is 6.154 g/cm3. Electron microprobe analyses provided: PbO 63.69, CaO 0.07, CuO 1.11, Fe2O3 7.63, Al2O3 1.63, V2O5 12.65, As2O5 3.09, P2O58.63, H2O 1.50 (structure), total 100.00 wt.% (normalized). The empirical formula (based on nine O a.p.f.u.) is: (Pb1.99Ca0.01)Σ2.00(Fe0.66Al0.22Cu0.10)Σ0.98(V0.97P0.85As0.19)Σ2.01O7.84(OH)1.16. Ferribushmakinite is monoclinic, P21/m, a = 7.7719(10), b = 5.9060(7), c = 8.7929(12) Å, β = 111.604(8)°, V = 375.24(9) Å3 and Z = 2. The eight strongest lines in the powder X-ray diffraction pattern are [dobs in Å (I)(hkl)]: 4.794(46)(011); 3.245(84)(211); 2.947(100)(020,212,103); 2.743(49)(112); 2.288(30)(220); 1.8532(27)(314,403); 1.8084(27)(multiple); and 1.7204(28)(312,114,321). Ferribushmakinite is a member of the brackebuschite supergroup. Its structure (R1 = 3.83% for 577 Fo > 4σF) differs from that of bushmakinite only in the dominance of Fe3+ over Al in the octahedral site.

Hydroniumpharmacosiderite, a new member of the pharmacosiderite supergroup from Cornwall, UK: structure and description

2010 ◽  
Vol 74 (5) ◽  
pp. 863-869 ◽  
Author(s):  
S. J. Mills ◽  
A. R. Kampf ◽  
P. A. Williams ◽  
P. Leverett ◽  
G. Poirier ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Diffraction Pattern ◽  
Powder Diffraction ◽  
Empirical Formula ◽  
Direct Methods ◽  
Structure Type ◽  
New Mineral ◽  
Calculated Density ◽  
X Ray ◽  
Mohs Hardness

AbstractHydroniumpharmacosiderite, ideally (H3O)Fe4(AsO4)3(OH)4·4H2O, is a new mineral from Cornwall, UK, probably from the St. Day group of mines. It occurs as a single yellowish green, slightly elongated cube, measuring 0.17 mm ×0.14 mm ×0.14 mm. The mineral is transparent with a vitreous lustre. It is brittle with a cleavage on {001}, has an irregular fracture, a white streak and a Mohs hardness of 2–3 (determined on H3O-exchanged pharmacosiderite). Hydroniumpharmacosiderite has a calculated density of 2.559 g cm–3 for the empirical formula. The empirical formula, based upon 20.5 oxygen atoms, is: [(H3O)0.50K0.48Na0.06]1.04(Fe3.79Al0.22)4.01[(As2.73P0.15)2.88O12](OH)4·4H2.14O. The five strongest lines in the X-ray powder diffraction pattern are [dobs(Å),Iobs,(hkl)]: 8.050,100,(001); 3.265,35,(112); 2.412,30,(113); 2.830,23,(202); 4.628,22,(111). Hydroniumpharmacosiderite is cubic, space group with a = 7.9587(2) Å, V = 504.11(2) Å3 and Z = 1. The crystal structure was solved by direct methods and refined to R1 = 0.0481 for 520 reflections with I > 2σ(I). The structure is consistent with determinations for H3O-exhchanged pharmacosiderite and the general pharmacosiderite structure type.

Gajardoite, KCa0.5As3+4O6Cl2·5H2O, a new mineral related to lucabindiite and torrecillasite from the Torrecillas mine, Iquique Province, Chile

2016 ◽  
Vol 80 (7) ◽  
pp. 1265-1272 ◽  
Author(s):  
Anthony R. Kampf ◽  
Barbara P. Nash ◽  
Maurizio Dini ◽  
Arturo Molina A. Donoso
Keyword(s):  
Electron Microprobe ◽  
Room Temperature ◽  
New Mineral ◽  
X Ray Diffraction ◽  
Calculated Density ◽  
Secondary Alteration ◽  
X Ray ◽  
Mohs Hardness ◽  
Measured Density ◽  
Irregular Cleavage

AbstractThe new mineral gajardoite (IMA2015-040), KCa0.5As3+4O6Cl2·5H2O, was found at the Torrecillas mine, Iquique Province, Chile, where it occurs as a secondary alteration phase in association with native arsenic, arsenolite,chongite, talmessite and torrecillasite. Gajardoite occurs as hexagonal plates up to ∼100 μm in diameter and 5 μm thick, in rosette-like subparallel intergrowths. Crystals are transparent, with vitreous lustre and white streak. The Mohs hardness is ∼1½, tenacity is brittleand fracture is irregular. Cleavage is perfect on {001}. The measured density is 2.64 g/cm3 and the calculated density is 2.676 g/cm3. Optically, gajardoite is uniaxial (–) with ω = 1.780(3) and ε = 1.570(5) (measured in white light). The mineral is very slowly soluble in H2O and slowly soluble in dilute HCl at room temperature. The empirical formula, determined from electron-microprobe analyses, is (K0.77Ca0.71Na0.05Mg0.05)∑1.58As4O11Cl1.96H9.62.Gajardoite is hexagonal, P6/mmm, a = 5.2558(8), c = 15.9666(18) Å, V = 381.96(13) Å3 and Z = 1. The eight strongest powder X-ray diffraction lines are [dobs Å(I)(hkl)]: 16.00(100)(001), 5.31(48)(003),3.466 (31)(103), 3.013(44)(104), 2.624(51)(006,110,111), 2.353(36)(113), 1.8647(21)(116,205) and 1.4605(17) (119,303,216). The structure, refined to R1 = 3.49% for 169 Fo > 4σF reflections, contains two types of layers. One layer of formulaKAs3+4O6Cl2 consists of two neutral As2O3 sheets, between which are K+ cations and on the outside of which are Cl– anions. This layer is topologically identical to a slice of the lucabindiite structureand similar to a slice of the torrecillasite structure. The second layer consists of an edge-sharing sheet of Ca(H2O)6 trigonal pyramids with isolated H2O groups centred in the hexagonal cavities in the sheet.

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