Agmantinite, Ag2MnSnS4, a new mineral with a wurtzite derivative structure from the Uchucchacua polymetallic deposit, Lima Department, Peru

2018 ◽  
Vol 83 (02) ◽  
pp. 233-238
Author(s):  
Frank N. Keutsch ◽  
Dan Topa ◽  
Rie Takagi Fredrickson ◽  
Emil Makovicky ◽  
Werner H. Paar
Keyword(s):  
Crystal Structure ◽  
Empirical Formula ◽  
New Mineral ◽  
Orthorhombic Space Group ◽  
Substitution Pattern ◽  
Calculated Density ◽  
X Ray ◽  
International Mineralogical Association ◽  
Cell Parameters ◽  
Polymetallic Deposit

AbstractAgmantinite, ideally Ag2MnSnS4, is a new mineral from the Uchucchacua polymetallic deposit, Oyon district, Catajambo, Lima Department, Peru. It occurs as orange–red crystals up to 100 μm across. Agmantinite is translucent with adamantine lustre and possesses a red streak. It is brittle. Neither fracture nor cleavage were observed. Based on the empirical formula the calculated density is 4.574 g/cm3. On the basis of chemically similar compounds the Mohs hardness is estimated at between 2 to 2½. In plane-polarised light agmantinite is white with red internal reflections. It is weakly bireflectant with no observable pleochroism with red internal reflections. Between crossed polars, agmantinite is weakly anisotropic with reddish brown to greenish grey rotation tints. The reflectances (RminandRmax) for the four standard wavelengths are: 19.7 and 22.0 (470 nm); 20.5 and 23.2 (546 nm); 21.7 and 2.49 (589 nm); and 20.6 and 23.6 (650 nm), respectively.Agmantinite is orthorhombic, space groupP21nm, with unit-cell parameters:a= 6.632(2),b= 6.922(2),c= 8.156(2) Å,V= 374.41(17) Å3,a:b:c0.958:1:1.178 andZ= 2. The crystal structure was refined toR= 0.0575 for 519 reflections withI >2σ(I). Agmantinite is the first known mineral of${M}_{\rm 2}^{\rm I} $MIIMIVS4type that is derived from wurtzite rather than sphalerite by ordered substitution of Zn, analogous to the substitution pattern for deriving stannite from sphalerite. The six strongest X-ray powder-diffraction lines derived from single-crystal X-ray diffraction data [din Å (intensity)] are: 3.51 (s), 3.32 (w), 3.11 (vs), 2.42 (w), 2.04 (m) and 1.88 (m). The empirical formula (based on 8 apfu) is (Ag1.94Cu0.03)Σ1.97(Mn0.98Zn0.05)Σ1.03Sn0.97S4.03.The crystal structure-derived formula is Ag2(Mn0.69Zn0.31)Σ1.00SnS4and the simplified formula is Ag2MnSnS4.The name is for the composition and the new mineral and mineral name have been approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (IMA2014-083).

Shannonite, Pb2OCO3, a new mineral from the Grand Reef Mine, Graham County, Arizona, USA

1995 ◽  
Vol 59 (395) ◽  
pp. 305-310 ◽  
Author(s):  
A. C. Roberts ◽  
J. A. R. Stirling ◽  
G. J. C. Carpenter ◽  
A. J. Criddle ◽  
G. C. Jones ◽  
...  
Keyword(s):  
Empirical Formula ◽  
Short Wave ◽  
New Mineral ◽  
Orthorhombic Space Group ◽  
Weak Anisotropy ◽  
Calculated Density ◽  
X Ray ◽  
Cell Parameters ◽  
New Mineral Species ◽  
Transmission Electron

AbstractShannonite, ideally Pb2OCO3, is a new mineral species that occurs as mm-sized white porcellanous crusts, associated with fluorite, at the Grand Reef mine, Graham County, Arizona, USA. Other associated minerals are plumbojarosite, hematite, Mn-oxides, muscovite-2M1, quartz, litharge, massicot, hydrocerussite, minium, and unnamed PbCO3·2PbO. Shannonite is orthorhombic, space group P21221 or P212121, with unit-cell parameters (refined from X-ray powder data): a 9.294(3), b 9.000(3), c 5.133(2) Å, V 429.3(3) Å3, a:b:c 1.0327:1:0.5703, Z = 4. The strongest five lines in the X-ray powder pattern [d in Å (I)(hkl)] are: 4.02(40)(111); 3.215(100)(211); 3.181(90)(121); 2.858(40)(130); 2.564(35)(002). The average of eight electron microprobe analyses is PbO 89.9(5), CO2 (by CHN elemental analyser) 9.70, total 99.60 wt.%. With O = 4, the empirical formula is Pb1.91C1.05O4.00. The calculated density for the empirical formula is 7.31 and for the idealized formula is 7.59 g/cm3. In reflected light, shannonite is colourless-grey to white, with ubiquitous white internal reflections (× 16 objectives), weak anisotropy, barely detectable bireflectance, and no evidence of pleochroism. The calculated refractive index (at 590 nm) is 2.09. Measured reflectance values in air and in oil (× 4 objectives) are tabulated. Transmission electron-microscopy studies reveal that individual crystallites range in size from 10–400 nm, are platy, and are anhedral. Physical properties for cryptocrystalline crusts include: white streak; waxy lustre; opaque; nonfluorescent under both long- and short-wave ultraviolet light; uneven fracture; brittle; VHN100 97 (range 93–100); calculated Mohs’ hardness 3–3½. Shannonite is soluble in concentrated HCl and in dilute HNO3 and H2SO4. The mineral name is for David M. Shannon, who helped collect the samples and who initiated this study.

Description and crystal structure of a new mineral – plimerite, ZnFe3+4(PO4)3(OH)5 – the Zn-analogue of rockbridgeite and frondelite, from Broken Hill, New South Wales, Australia

2009 ◽  
Vol 73 (1) ◽  
pp. 131-148 ◽  
Author(s):  
P. Elliott ◽  
U. Kolitsch ◽  
G. Giester ◽  
E. Libowitzky ◽  
C. McCammon ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Empirical Formula ◽  
Direct Methods ◽  
Ore Deposits ◽  
New Mineral ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Broken Hill

Plimerite, ideally Zn (PO4)3(OH)5, is a new mineral from the Block 14 Opencut, Broken Hill, New SouthWales. It occurs as pale-green to dark-olive-green, almost black, acicular to prismatic and bladed crystals up to 0.5 mm long and as hemispherical aggregates of radiating acicular crystals up to 3 mm across. Crystals are elongated along [001] and the principal form observed is {100} with minor {010} and {001}. The mineral is associated with hinsdalite-plumbogummite, pyromorphite, libethenite, brochantite, malachite, tsumebite and strengite. Plimerite is translucent with a pale-greyish-green streak and a vitreous lustre. It shows an excellent cleavage parallel to {100} and {010} and distinct cleavage parallel to {001}. It is brittle, has an uneven fracture, a Mohs’ hardness of 3.5–4, D(meas.) = 3.67(5) g/cm3 and D(calc.) = 3.62 g/cm3 (for the empirical formula). Optically, it is biaxial negative with α = 1.756(5), β = 1.764(4), γ = 1.767(4) and 2V(calc.) of –63º; pleochroism is X pale-greenish-brown, Y pale-brown, Z pale-bluish-green; absorption Z > X > Y; optical orientation XYZ = cab. Plimerite is orthorhombic, space group Bbmm, unit-cell parameters: a = 13.865(3) Å, b = 16.798(3) Å, c = 5.151(10) Å, V = 1187.0(4) Å3 (single-crystal data) and Z = 4. Strongest lines in the X-ray powder diffraction pattern are [d (A˚ ), I, hkl]: 4.638, (50), (111); 3.388, (50), (041); 3.369, (55), (131); 3.168, (100), (132); 2.753, (60), (115); 2.575, (90), (200); 2.414, (75), (220); 2.400, (50), (221); 1.957, (40), (225). Electron microprobe analysis yielded (wt.%): PbO 0.36, CaO 0.17, ZnO 20.17, MnO 0.02, Fe2O3 29.82, FeO 2.98, Al2O3 4.48, P2O5 32.37, As2O5 0.09, H2O (calc) 6.84, total 97.30 (Fe3+/Fe2+ ratio determined by Mössbauer spectroscopy). The empirical formula calculated on the basis of 17 oxygens is Ca0.02Pb0.01Zn1.68Al0.60P3.09As0.01O17.00H5.15. The crystal structure was solved by direct methods and refined to an R1 index of 6.41% for 1332 observed reflections from single-crystal X-ray diffraction data (Mo-Kα radiation, CCD area detector). The structure of plimerite is isotypic with that of rockbridgeite and is based on face-sharing trimers of (Mϕ6) octahedra which link by sharing edges to form chains, that extend in the b-direction. Chains link to clusters comprising pairs of corner-sharing (Mϕ6) octahedra that link to PO4 tetrahedra forming sheets parallel to (001). The sheets link via octahedra and tetrahedra corners into a heteropolyhedral framework structure. The mineral name honours Professor Ian Plimer for his contributions to the study of the geology of ore deposits.

Fassinaite, Pb22+(S2O3)(CO3), the first mineral with coexisting thiosulphate and carbonate groups:d escription and crystal structure

2011 ◽  
Vol 75 (6) ◽  
pp. 2721-2732 ◽  
Author(s):  
L. Bindi ◽  
F. Nestola ◽  
U. Kolitsch ◽  
A. Guastoni ◽  
F. Zorzi
Keyword(s):  
Empirical Formula ◽  
Optical Data ◽  
New Mineral ◽  
Orthorhombic Space Group ◽  
Calculated Density ◽  
X Ray ◽  
Cell Parameters ◽  
Mohs Hardness ◽  
Ray Density ◽  
Oxygen Atoms

AbstractFassinaite, ideally Pb22+(S2O3)(CO3), is a new mineral from the Trentini mine, Mount Naro, Vicenza Province, Veneto, Italy (holotype locality). It is also reported from the Erasmus adit, Schwarzleo District, Leogang, Salzburg, Austria and the Friedrich-Christian mine, Schapbach, Black Forest, Baden-Wurttemberg, Germany (cotype localities). At the Italian type locality it occurs as acicular [010]. colourless crystals up to 200 μn long, closely associated with galena, quartz and anglesite. At the Austrian cotype locality it is associated with cerussite, rare sulphur and very rare phosgenite. At the German cotype locality anglesite is the only associated phase. Fassinaite crystals commonly have flat chisel-shaped terminations. They are transparent with vitreous to adamantine lustre and a white streak. Fassinaite is brittle with an irregular fracture and no discernible cleavage; the estimated Mohs hardness is 11/2—2. The calculated density for the type material is 6.084 g cm–3 (on the basis of the empirical formula), whereas the X-ray density is 5.947 g cm–3. In common with other natural lead thiosulphates (i.e. sidpietersite and steverustite) fassinaite has intense internal reflections, which do not allow satisfactory optical data to be collected; the crystals are length-slow and have very high birefringence. The mineral is not fluorescent.Fassinaite is orthorhombic, space group Pnma, with unit-cell parameters (for the holotype material) a = 16.320(2), b = 8.7616(6), c = 4.5809(7) Å, V = 655.0(1) Å3, a:b:c = 1.863:1:0.523, Z = 4. Single-crystal structural studies were carried out on crystals from all three localities: R1(F) values range between 0.0353 and 0.0596. The structure consists of rod-like arrangements of Pb-centred polyhedra that extend along the [010] direction. These ‘rods’ are linked, alternately, by (CO3)2– and (S2O3)2– groups. The (S2O3)2– groups point alternately left and right (in a projection on [001] with [010] set vertical) if the apex occupied by the S2– in the thiosulphate group is defined to be the atom giving the direction. The lead atoms are nine-coordinated by seven oxygen atoms and two sulphur (S2–) atoms. The eight strongest X-ray powder-diffraction lines [d in Å (I/I0) (hkl)] are: 4.410 (39) (101), 4.381 (59) (020), 4.080 (62) (400), 3.504 (75) (301), 3.108 (100) (121), 2.986 (82) (420), 2.952 (49) (221) and 2.736 (60) (321). Electron-microprobe analyses produce an empirical formula Pb2.01(1)(S1.82(2)O3)CO3 (on the basis of six oxygen atoms). The presence of both carbonate and thiosulphate groups was corroborated by Raman spectra, which are discussed in detail. Fassinaite is named after Bruno Fassina (b. 1943), an Italian mineral collector who discovered the mineral in 2009.

Putnisite, SrCa4Cr83+ (CO3)8SO4(OH)16·25H2O, a new mineral from Western Australia: description and crystal structure

2014 ◽  
Vol 78 (1) ◽  
pp. 131-144 ◽  
Author(s):  
P. Elliott ◽  
G. Giester ◽  
R. Rowe ◽  
A. Pring
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Western Australia ◽  
Empirical Formula ◽  
New Mineral ◽  
Orthorhombic Space Group ◽  
Calculated Density ◽  
X Ray ◽  
Area Detector ◽  
Mohs Hardness

AbstractPutnisite, SrCa4Cr83+ (CO7)8SO4(OH)16·25H2O, is a new mineral from the Polar Bear peninsula, Southern Lake Cowan, Western Australia, Australia. The mineral forms isolated pseudocubic crystals up to 0.5 mm in size in a matrix composed of quartz and a near amorphous Cr silicate. Putnisite is translucent, with a pink streak and vitreous lustre. It is brittle and shows one excellent and two good cleavages parallel to {100}, {010} and {001}. The fracture is uneven and the Mohs hardness 1½−2. The measured density is 2.20(3) g/cm3 and the calculated density based on the empirical formula is 2.23 g/cm3. Optically, putnisite is biaxial negative, with α = 1.552(3), β = 1.583(3) and γ = 1.599(3) (measured in white light). The optical orientation is uncertain and pleochroism is distinct: X pale bluish grey, Y pale purple, Z pale purple. Putnisite is orthorhombic, space group Pnma, with a = 15.351(3), b = 20.421(4) Å, c = 18.270(4) Å, V = 5727(2) Å3 (single-crystal data), and Z = 4. The strongest five lines in the X-ray powder diffraction pattern are [d(Å)(I)(hkl)]: 13.577 (100) (011), 7.659 (80) (200), 6.667 (43) (211), 5.084 (19) (222, 230), 3.689 (16) (411). Electron microprobe analysis (EMPA) gave (wt.%): Na2O 0.17, MgO 0.08, CaO 10.81, SrO 5.72, BaO 0.12, CuO 0.29, Cr2O3 31.13, SO3 3.95, SiO2 0.08, Cl− 0.28, CO2calc 17.94, H2Ocalc 30.30, O=Cl−0.06, total 100.81. The empirical formula, based on O + Cl = 69, is: Cr8.023+Ca3.78Sr1.08Na0.11Cu0.072+Mg0.04Ba0.02[(SO4)0.96(SiO4)0.03]0.99 (CO3)7.98(OH)16.19Cl0.15·24.84H2O. The crystal structure was determined from single-crystal X-ray diffraction data (MoKα, CCD area detector and refined to R1 = 5.84% for 3181 reflections with F0 > 4σF. Cr(OH)4O2 octahedra link by edge-sharing to form an eight-membered ring. A 10-coordinated Sr2+ cation lies at the centre of each ring. The rings are decorated by CO3 triangles, each of which links by corner-sharing to two Cr(OH)4O2 octahedra. Rings are linked by Ca(H2O)4O4 polyhedra to form a sheet parallel to (100). Adjacent sheets are joined along [100] by corner-sharing SO4 tetrahedra. H2O molecules occupy channels that run along [100] and interstices between slabs. Moderate to weak hydrogen bonding provides additional linkage between slabs.

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.

Kurilite – Ag8Te3Se – a new mineral from the Prasolovskoe deposit, Kuril islands, Russian Federation

2010 ◽  
Vol 74 (3) ◽  
pp. 463-468 ◽  
Author(s):  
V. A. Kovalenker ◽  
O. Yu. Plotinskaya ◽  
C. J. Stanley ◽  
A. C. Roberts ◽  
A. M. McDonald ◽  
...  
Keyword(s):  
Russian Federation ◽  
Empirical Formula ◽  
Polarized Light ◽  
New Mineral ◽  
Unit Cell Parameters ◽  
Calculated Density ◽  
X Ray ◽  
Cell Parameters ◽  
Kunashir Island ◽  
Mohs Hardness

AbstractKurilite, with the simplified formula, Ag8Te3Se, is a new mineral from the Prasolovskoe epithermal Au-Ag deposit, Kunashir Island, Kuril arc, Russian Federation. It occurs as aggregates up to 2 mm in size, composed of brittle xenomorphic grains, up to several μm in size, in quartz, associated with tetrahedrite, hessite, sylvanite and petzite. Kurilite is opaque, grey, with a metallic lustre and a black streak. Under plane-polarized light, kurilite is white with no observed bireflectance, cleavage, or parting observed. Under crossed polars it appears isotropic without internal reflections. Reflectance values in air and in oil, are tabulated. It has a mean VHN (25 g load) of 99.9 kg/mm2 which equates roughly to a Mohs hardness of 3. Electron microprobe analyses yield a mean composition of Ag 63.71, Au 0.29, Te 29.48, Se 5.04, S 0.07, total 98.71 wt.%. The empirical formula (based on 12 atoms) is (Ag7.97Au0.02)Σ7.99Te3.00(Se0.86Te0.12S0.03)Σ1.01. The calculated density is 7.799 g/cm3 (based on the empirical formula and unit-cell parameters refined from single-crystal data). Kurilite is rhombohedral, R3 or , a 15.80(1), c 19.57(6) Å, V 4231(12)Å3, c:a 1.2386, Z = 15. Its crystal structure remains unsolved. The seven strongest lines of the X-ray powder-diffraction pattern [d in Å (I)(hkl)] are: 3.727(20)(131), 2.996(50)(232), 2.510(30)(226,422), 2.201(100)(128,416,342), 2.152(20)(603), 2.079(30)(253), 2.046(20)(336,434). The mineral is named after the locality.

Oxyplumboroméite, Pb2Sb2O7, a new mineral species of the pyrochlore supergroup from Harstigen mine, Värmland, Sweden

2013 ◽  
Vol 77 (7) ◽  
pp. 2931-2939 ◽  
Author(s):  
U. Hålenius ◽  
F. Bosi
Keyword(s):  
Crystal Structure ◽  
Structure Refinement ◽  
New Mineral ◽  
Crystal Structure Refinement ◽  
Unit Cell Parameters ◽  
Calculated Density ◽  
X Ray ◽  
Cell Parameters ◽  
New Mineral Species ◽  
Mohs Hardness

AbstractOxyplumboroméite, Pb2Sb2O7, is a new mineral of the roméite group of the pyrochlore supergroup (IMA 2013-042). It is found together with calcite and leucophoenicite in fissure fillings in tephroite skarn at the Harstigen mine, Värmland, Sweden. The mineral occurs as yellow to brownish yellow rounded grains or imperfect octahedra. Oxyplumboroméite has a Mohs hardness of ∼5, a calculated density of 6.732 g/cm3 and is isotropic with a calculated refractive index of 2.061. Oxyplumboroméite is cubic, space group Fdm, with the unit-cell parameters a = 10.3783(6) Å, V = 1117.84(11) Å3 and Z = 8. The strongest five X-ray powder-diffraction lines [d in Å(I)(hkl)] are: 2.9915(100)(222), 2.5928(32)(400), 1.8332(48)(440), 1.5638(38)(622) and 1.1900(12)(662). The crystal structure of oxyplumboroméite was refined to an R1 index of 3.02% using 160 unique reflections collected with MoKα radiation. Electron microprobe analyses in combination with crystal-structure refinement, infrared, Mössbauer and electronic absorption spectroscopy resulted in the empirical formula A(Pb0.92Ca0.87Mn0.09Sr0.01Na0.05)Σ1.93B(Sb1.73Fe3+0.27)Σ2.00X+Y[O6.64(OH)0.03]Σ6.67. Oxyplumboroméite is the Pb analogue of oxycalcioroméite, ideally Ca2Sb2O7.

scholarly journals Kesebolite-(Ce), CeCa2Mn(AsO4)[SiO3]3, a New REE-Bearing Arsenosilicate Mineral from the Kesebol Mine, Åmål, Västra Götaland, Sweden

Minerals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 385 ◽  
Author(s):  
Dan Holtstam ◽  
Luca Bindi ◽  
Andreas Karlsson ◽  
Jörgen Langhof ◽  
Thomas Zack ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Diffraction Data ◽  
New Mineral ◽  
Unit Cell Parameters ◽  
Single Crystal Diffraction ◽  
Calculated Density ◽  
X Ray ◽  
Cell Parameters ◽  
Mine Dumps

Kesebolite-(Ce), ideal formula CeCa2Mn(AsO4)[SiO3]3, is a new mineral (IMA No. 2019-097) recovered from mine dumps at the Kesebol Mn-(Fe-Cu) deposit in Västra Götaland, Sweden. It occurs with rhodonite, baryte, quartz, calcite, talc, andradite, rhodochrosite, K-feldspar, hematite, gasparite-(Ce), chernovite-(Y) and ferriakasakaite-(Ce). It forms mostly euhedral crystals, with lengthwise striation. The mineral is dark grayish-brown to brown, translucent, with light brown streak. It is optically biaxial (+), with weak pleochroism, and ncalc = 1.74. H = 5–6 and VHN100 = 825. Fair cleavage is observed on {100}. The calculated density is 3.998(5) g·cm−3. Kesebolite-(Ce) is monoclinic, P21/c, with unit-cell parameters from X-ray single-crystal diffraction data: a = 6.7382(3), b = 13.0368(6), c = 12.0958(6) Å, β = 98.578(2)°, and V = 1050.66(9) Å3, with Z = 4. Strongest Bragg peaks in the X-ray powder pattern are: [I(%), d(Å) (hkl)] 100, 3.114 (20-2); 92, 2.924 (140); 84, 3.138 (041); 72, 2.908 (014); 57, 3.228 (210); 48, 2.856 (042); 48, 3.002 (132). The unique crystal structure was solved and refined to R1 = 4.6%. It consists of 6-periodic single silicate chains along (001); these are interconnected to infinite (010) strings of alternating, corner-sharing MnO6 and AsO4 polyhedra, altogether forming a trellis-like framework parallel to (100).

scholarly journals Richardsite, Zn2CuGaS4, A New Gallium-Essential Member of the Stannite Group from the Gem Mines near Merelani, Tanzania

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 467 ◽  
Author(s):  
Luca Bindi ◽  
John A. Jaszczak
Keyword(s):  
Crystal Structure ◽  
Polarized Light ◽  
New Mineral ◽  
X Ray Diffraction ◽  
Calculated Density ◽  
X Ray ◽  
International Mineralogical Association ◽  
Metal Atoms ◽  
Group I ◽  
The Ideal

The new mineral richardsite occurs as overgrowths of small (50–400 μm) dark gray, disphenoidal crystals with no evident twinning, but epitaxically oriented on wurtzite–sphalerite crystals from the gem mines near Merelani, Lelatema Mountains, Simanjiro District, Manyara Region, Tanzania. Associated minerals also include graphite, diopside, and Ge,Ga-rich wurtzite. It is brittle, dark gray in color, and has a metallic luster. It appears dark bluish gray in reflected plane-polarized light, and is moderately bireflectant. It is distinctly anisotropic with violet to light-blue rotation tints with crossed polarizers. Reflectance percentages for Rmin and Rmax in air at the respective wavelengths are 23.5, 25.0 (471.1 nm); 27.4, 28.9 (548.3 nm); 28.1, 29.4 (586.6 nm); 27.7, 28.9 (652.3 nm). Richardsite does not show pleochroism, internal reflections, or optical indications of growth zonation. Electron microprobe analyses determine an empirical formula, based on 8 apfu, as (Zn1.975Cu0.995Ga0.995Fe0.025Mn0.010Ge0.005Sn0.005)Σ4.010S3.990, while its simplified formula is (Zn,Cu)2(Cu,Fe,Mn)(Ga,Ge,Sn)S4, and the ideal formula is Zn2CuGaS4. The crystal structure of richardsite was investigated using single-crystal and powder X-ray diffraction. It is tetragonal, with a = 5.3626(2) Å, c = 10.5873(5) Å, V = 304.46(2) Å3, Z = 2, and a calculated density of 4.278 g·cm−3. The four most intense X-ray powder diffraction lines [d in Å (I/I0)] are 3.084 (100); 1.882 (40); 1.989 (20); 1.614 (20). The refined crystal structure (R1 = 0.0284 for 655 reflections) and obtained chemical formula indicate that richardsite is a new member of the stannite group with space group I 4 ¯ 2 m . Its structure consists of a ccp array of sulfur atoms tetrahedrally bonded with metal atoms occupying one-half of the ccp tetrahedral voids. The ordering of the metal atoms leads to a sphalerite(sph)-derivative tetragonal unit-cell, with a ≈ asph and c ≈ 2asph. The packing of S atoms slightly deviates from the ideal, mainly due to the presence of Ga. Using 632.8-nm wavelength laser excitation, the most intense Raman response is a narrow peak at 309 cm−1, with other relatively strong bands at 276, 350, and 366 cm−1, and broader and weaker bands at 172, 676, and 722 cm−1. Richardsite is named in honor of Dr. R. Peter Richards in recognition of his extensive research and writing on topics related to understanding the genesis of the morphology of minerals. Its status as a new mineral and its name have been approved by the Commission of New Minerals, Nomenclature and Classification of the International Mineralogical Association (No. 2019-136).

scholarly journals Joteite, Ca2CuAl[AsO4][AsO3(OH)]2(OH)2·5H2O, a new arsenate with a sheet structure and unconnected acid arsenate groups

2013 ◽  
Vol 77 (6) ◽  
pp. 2811-2823 ◽  
Author(s):  
A. R. Kampf ◽  
S. J. Mills ◽  
R. M. Housley ◽  
G. R. Rossman ◽  
B. P. Nash ◽  
...  
Keyword(s):  
Empirical Formula ◽  
New Mineral ◽  
Optical Orientation ◽  
Secondary Mineral ◽  
Calculated Density ◽  
X Ray ◽  
Cell Parameters ◽  
Perfect Cleavage ◽  
Mohs Hardness ◽  
Greenish Blue

AbstractJoteite (IMA2012-091), Ca2CuAl[AsO4][AsO3(OH)]2(OH)2·5H2O, is a new mineral from the Jote mine, Tierra Amarilla, Copiapó Province, Atacama, Chile. The mineral is a late-stage, low-temperature, secondary mineral occurring with conichalcite, mansfieldite, pharmacoalumite, pharmacosiderite and scorodite in narrow seams and vughs in the oxidized upper portion of a hydrothermal sulfide vein hosted by volcanoclastic rocks. Crystals occur as sky-blue to greenish-blue thin blades, flattened and twinned on {001}, up to ~300 μm in length, and exhibiting the forms {001}, {010}, {10}, {20} and {111}. The blades are commonly intergrown in wheat-sheaf-like bundles, less commonly in sprays, and sometimes aggregated as dense crusts and cavity linings. The mineral is transparent and has a very pale blue streak and vitreous lustre. The Mohs hardness is estimated at 2 to 3, the tenacity is brittle, and the fracture is curved. It has one perfect cleavage on {001}. The calculated density based on the empirical formula is 3.056 g/cm3. It is optically biaxial (–) with α = 1.634(1), β = 1.644(1), γ = 1.651(1) (white light), 2Vmeas = 78(2)° and 2Vcalc = 79.4°. The mineral exhibits weak dispersion, r < v. The optical orientation is X ≈ c*; Y ≈ b*. The pleochroism is Z (greenish blue) > Y (pale greenish blue) > X (colourless). The normalized electron-microprobe analyses (average of 5) provided: CaO 15.70, CuO 11.22, Al2O38.32, As2O546.62, H2O 18.14 (structure), total 100 wt.%. The empirical formula (based on 19 O a.p.f.u.) is: Ca1.98Cu1.00Al1.15As2.87H14.24O19. The mineral is slowly soluble in cold, concentrated HCl. Joteite is triclinic, P1, with the cell parameters: a = 6.0530(2), b = 10.2329(3), c = 12.9112(4) Å, α = 87.572(2), β = 78.480(2), γ = 78.697(2)°, V = 768.40(4) Å3 and Z = 2. The eight strongest lines in the X-ray powder diffraction pattern are [dobs Å (I)(hkl)]: 12.76(100)(001), 5.009(23)(020), 4.206(26)(120,003,121), 3.92(24)(022,02,02), 3.40(25)(1̄13), 3.233(19)(031,023,123,02̄3), 2.97(132,201) and 2.91(15)(22,13). In the structure of joteite (R1 = 7.72% for 6003 Fo > 4σF), AsO4 and AsO3 (OH) tetrahedra, AlO6 octahedra and Cu2+O5 square pyramids share corners to form sheets parallel to {001}. In addition, 7- and 8-coordinate Ca polyhedra link to the periphery of the sheets yielding thick slabs. Between the slabs are unconnected AsO3(OH) tetrahedra, which link the slabs only via hydrogen bonding. The Raman spectrum shows features consistent with OH and/or H2O in multiple structural environments. The region between the slabs may host excess Al in place of some As.

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