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 > 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>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.

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.

Staročeskéite, Ag0.70Pb1.60(Bi1.35Sb1.35)Σ2.70S6, from Kutná Hora, Czech Republic, a new member of the lillianite homologous series

2018 ◽  
Vol 82 (4) ◽  
pp. 993-1005 ◽  
Author(s):  
Richard Pažout ◽  
Jiří Sejkora
Keyword(s):  
Czech Republic ◽  
Homologous Series ◽  
Electron Probe ◽  
New Mineral ◽  
Orthorhombic Space Group ◽  
Calculated Density ◽  
New Mineral Species ◽  
Reflected Light ◽  
Ore District ◽  
The Ideal

ABSTRACTA new mineral species, staročeskéite, ideally Ag0.70Pb1.60(Bi1.35Sb1.35)Σ2.70S6, has been found at Kutná Hora ore district, Czech Republic. The mineral occurs in the late-stage Bi-mineralization associated with other lillianite homologues (gustavite, terrywallaceite, vikingite, treasurite, eskimoite and Bi-rich andorite-group minerals) and other bismuth sulfosalts (izoklakeite, cosalite and Bi-rich jamesonite) in quartz gangue. The mineral occurs as lath shaped crystals or anhedral grains up to 80 µm × 70 µm, growing together in aggregates up to 200 µm × 150 µm across. Staročeskéite is steel-grey in colour and has a metallic lustre, the calculated density is 6.185 g/cm3. In reflected light staročeskéite is greyish white; bireflectance and pleochroism are weak with greyish tints. Anisotropy is weak to medium with grey to bluish grey rotation tints. Internal reflections were not observed. The empirical formula based on electron probe microanalyses and calculated on 11 apfu is: (Ag0.68Cu0.01)Σ0.69(Pb1.56Fe0.01Cd0.01)Σ1.58(Bi1.32Sb1.37)Σ2.69(S6.04Se0.01)Σ6.05. The ideal formula is Ag0.70Pb1.60(Bi1.35Sb1.35)Σ2.70S6, which requires Ag 7.22, Pb 31.70, Bi 26.97, Sb 15.72 and S 18.39 wt.%, total 100.00 wt.%. Staročeskéite is a member of the lillianite homologous series with N = 4. Unlike gustavite and terrywallaceite, staročeskéite, similarly to lillianite, is orthorhombic, space group Cmcm, with a = 4.2539(8), b = 13.3094(8), c = 19.625(1) Å, V = 1111.1(2) Å3 and Z = 4. The structure of staročeskéite contains four sulfur sites and three metal sites: one pure Pb site and two mixed sites, M1 (0.52Bi + 0.356Ag + 0.124Sb) and M2 (0.601Sb + 0.259Pb + 0.14Bi). The mineral is characterized by the Bi:Sb ratio 1:1 (Bi/(Bi + Sb) = 0.50) and the Ag+ + Bi3+, Sb3+ ↔ 2 Pb2+ substitution (L%) equal to 70%. Thus the mineral lies between two series of the lillianite structures with N = 4, between the lillianite–gustavite series and the andorite series.

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.

Canutite, NaMn3[AsO4][AsO3(OH)]2, a new protonated alluaudite-group mineral from the Torrecillas mine, Iquique Province, Chile

2014 ◽  
Vol 78 (4) ◽  
pp. 787-795 ◽  
Author(s):  
A. R. Kampf ◽  
S. J. Mills ◽  
F. Hatert ◽  
B. P. Nash ◽  
M. Dini ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
White Light ◽  
Electron Microprobe ◽  
New Mineral ◽  
Optical Orientation ◽  
Calculated Density ◽  
Secondary Alteration ◽  
Group Mineral ◽  
X Ray ◽  
Mohs Hardness

AbstractThe new mineral canutite (IMA2013-070), NaMn3[AsO4][AsO3(OH)]2, was found at two different locations at the Torrecillas mine, Salar Grande, Iquique Province, Chile, where it occurs as a secondary alteration phase in association with anhydrite, halite, lavendulan, magnesiokoritnigite, pyrite, quartz and scorodite. Canutite is reddish brown in colour. It forms as prisms elongated on [20] and exhibiting the forms {010}, {100}, {10}, {201} and {102}, or as tablets flattened on {102} and exhibiting the forms {102} and {110}. Crystals are transparent with a vitreous lustre. The mineral has a pale tan streak, Mohs hardness of 2½, brittle tenacity, splintery fracture and two perfect cleavages, on {010} and {101}. The calculated density is 4.112 g cm−3. Optically, canutite is biaxial (+) with α = 1.712(3), β = 1.725(3) and γ = 1.756(3) (measured in white light). The measured 2V is 65.6(4)°, the dispersion is r < v (slight), the optical orientation is Z = b; X ^ a = 18° in obtuse β and pleochroism is imperceptible. The mineral is slowly soluble in cold, dilute HCl. The empirical formula (for tabular crystals from near the mineshaft), determined from electron - microprobe analyses, is (Na1.05Mn2.64Mg0.34Cu0.14Co0.03)∑4.20As3O12H1.62. Canutite is monoclinic, C2/c, a = 12.3282(4), b = 12.6039(5), c = 6.8814(5) Å, β = 113.480(8)°, V = 980.72(10) Å3 and Z = 4. The eight strongest X-ray powder diffraction lines are [dobs Å(I)(hkl)]: 6.33(34)(020), 4.12(26)(21), 3.608(29)(310,31), 3.296(57)(12), 3.150(28)(002,131), 2.819(42)(400,041,330), 2.740(100)(240,02,112) and 1.5364(31)(multiple). The structure, refined to R1 = 2.33% for 1089 Fo > 4σF reflections, shows canutite to be isostructural with protonated members of the alluaudite group.

Tsugaruite, Pb4As2S7, a new mineral species from the Yunosawa mine, Aomori Prefecture, Japan

1998 ◽  
Vol 62 (6) ◽  
pp. 793-799 ◽  
Author(s):  
M. Shimizu ◽  
R. Miyawaki ◽  
A. Kato ◽  
S. Matsubara ◽  
F. Matsuyama ◽  
...  
Keyword(s):  
New Mineral ◽  
Calculated Density ◽  
X Ray ◽  
Ideal Formula ◽  
New Mineral Species ◽  
Hardness Scale ◽  
Mohs Hardness ◽  
Aomori Prefecture ◽  
Northern Japan ◽  
The Ideal

AbstractTsugaruite, Pb4As2S7, is a new Pb-As sulphosalt from the Yunosawa mine, Aomori Prefecture, northern Japan. X-ray studies indicated it to be orthorhombic Pnn2 or Pnnm, a 15.179(1), b 38.195(1), c 8.0745(1) Å, Z = 16 [Pb4As2S7] with a subcell with c′ = 1/2c. The six strongest diffractions in the X-ray powder pattern [d (in Å), (I), (hkl)] are: 4.47 (30) (340), 3.705 (34) (1.10.0), 3.395 (100) (450), 2.870 (34) (192), 2.819 (53) (550), and 2.739 (48) (560, 2.13.0). The average of seven electron microprobe analyses gave Pb 68.70, Tl 0.13, As 12.45, S 18.64, total 99.92 wt.%. The empirical formula calculated on the basis of total atoms = 13 is Pb3.99Tl0.01As2.00S7.00, corresponding to the ideal formula Pb4As2S7. The calculated density is 6.83 g/cm3 for the ideal formula.Tsugaruite is opaque with a metallic lustre and lead-grey streak. No cleavage was observed. It is brittle with uneven fracture. VHN25 is 75.4–94.9 kg/mm2, mean 86.4 (n) = 4), corresponding to 2.5–3 in Mohs' hardness scale. In reflected plane-polarised light in air, it is white with a greenish tint, more greenish than jordanite. Bireflectance and pleochroism are weak, weaker than those of jordanite; and anisotropism is weak to moderate, weaker than that of jordanite. No internal reflections. The reflectance spectra are tabulated in the text.Tsugaruite was found in a thin baryte veinlet exposed in the wall of a small open cut of the Yunosawa mine. It forms radiating groups of long tabular tapering crystals elongated along c and tabular to b, up to 0.04 mm wide and 2 mm long. The associated minerals are jordanite, which formed earlier than tsugaruite, and galena. The chemical similarity of tsugaruite and jordanite and their intergrown character indicates that earlier jordanite analyses may also include analyses of tsugarite.

Chongite, Ca3Mg2(AsO4)2(AsO3OH)2·4H2O, a new arsenate member of the hureaulite group from the Torrecillas mine, Iquique Province, Chile

2016 ◽  
Vol 80 (7) ◽  
pp. 1255-1263 ◽  
Author(s):  
Anthony R. Kampf ◽  
Barbara P. Nash ◽  
Maurizio Dini ◽  
Arturo A. Molina Donoso
Keyword(s):  
Room Temperature ◽  
Obtuse Angle ◽  
New Mineral ◽  
Optical Orientation ◽  
X Ray Diffraction ◽  
Calculated Density ◽  
Secondary Alteration ◽  
X Ray ◽  
Mohs Hardness ◽  
Measured Density

AbstractThe new mineral chongite (IMA2015–039), Ca3Mg2(AsO4)2(AsO3OH)2.4H2O, was found at the Torrecillas mine, Iquique Province, Chile, where it occurs as a secondary alteration phase in association with native arsenic, arsenolite, gajardoite, talmessite and torrecillasite. Chongite occurs as prismatic crystals up to ∼1 mm long grouped in tightly intergrown radial aggregates up to 2 mm in diameter. Crystals are transparent, with vitreous lustre and white streak. The Mohs hardness is∼3½,tenacity is brittle and fracture is conchoidal. Cleavage is good on ﹛100﹜. The measured density is 3.09(2) g/cm3and the calculated density is 3.087 g/cm3. Optically, chongite is biaxial (-) with α = 1.612(1), β= 1.626(1), γ= 1.635(1) and 2V = 76.9(1)° (measured in white light). Dispersion isr < v,distinct. The optical orientation isX= b;Z^a =27° in obtuse angle β. The mineral is slowly soluble in dilute HCl at room temperature. The empirical formula, determined from electron-microprobe analyses, is (Ca2.90Mg1.93Mn0.14)Σ4.97As4O20H10.07. Chongite is monoclinic,die, a =18.5879(6),b =9.3660(3),c =9.9622(7) Å, β = 96.916(7)°,V=1721.75(14) Å3and Z=4. The eight strongest powder X-ray diffraction lines are[dobsÅ(I)(hkl)]: 8.35(29)(110), 4.644(62) (3ˉ11,020,400,2̄02), 4.396(26)(311), 3.372(62)(022,312,5̄11), 3.275(100)(420,22ˉ2,421), 3.113(57)(222), 2.384(30)(711,530,7̄12) and 1.7990(22)(9̄13,334,5̄34). The structure determination(R1= 1.56% for 1849 Fo> 4σFreflections) confirms that chongite is a member of the hureaulite group.

Hrabákite, Ni9PbSbS8, a new member of the hauchecornite group from Příbram, Czech Republic

2021 ◽  
pp. 1-8
Author(s):  
Jiří Sejkora ◽  
Pavel Škácha ◽  
Jakub Plášil ◽  
Zdeněk Dolníček ◽  
Jana Ulmanová
Keyword(s):  
Czech Republic ◽  
Diffraction Data ◽  
New Mineral ◽  
X Ray Diffraction ◽  
Calculated Density ◽  
X Ray ◽  
Reflected Light ◽  
Mohs Hardness ◽  
Cation Sites ◽  
The Ideal

Abstract The new mineral hrabákite (IMA2020-034) was found in siderite–sphalerite gangue with minor dolomite–ankerite at the dump of shaft No. 9, one of the mines in the abandoned Příbram uranium and base-metal district, central Bohemia, Czech Republic. Hrabákite is associated with Pb-rich tučekite, Hg-rich silver, stephanite, nickeline, millerite, gersdorffite, sphalerite and galena. The new mineral occurs as rare prismatic crystals up to 120 μm in size and allotriomorphic grains. Hrabákite is grey with a brownish tint. Mohs hardness is ca. 5–6; the calculated density is 6.37 g.cm–3. In reflected light, hrabákite is grey with a brown hue. Bireflectance is weak and pleochroism was not observed. Anisotropy under crossed polars is very weak (brownish tints) to absent. Internal reflections were not observed. Reflectance values of hrabákite in air (Rmin–Rmax, %) are: 39.6–42.5 at 470 nm, 45.0–47.5 at 546 nm, 46.9–49.2 at 589 nm and 48.9–51.2 at 650 nm). The empirical formula for hrabákite, based on electron-microprobe analyses (n = 11), is (Ni8.91Co0.09Fe0.03)9.03(Pb0.94Hg0.04)0.98(Sb0.91As0.08)0.99S7.99. The ideal formula is Ni9PbSbS8, which requires Ni 47.44, Pb 18.60, Sb 10.93 and S 23.03, total of 100.00 wt.%. Hrabákite is tetragonal, P4/mmm, a = 7.3085(4), c = 5.3969(3) Å, with V = 288.27(3) Å3 and Z = 1. The strongest reflections of the calculated powder X-ray diffraction pattern [d, Å (I)(hkl)] are: 3.6543(57)(200); 3.2685(68)(210); 2.7957(100)(211); 2.3920(87)(112); 2.3112(78)(310); 1.8663(74)(222); and 1.8083(71)(302). According to the single-crystal X-ray diffraction data (Rint = 0.0218), the unit cell of hrabákite is undoubtedly similar to the cell reported for tučekite. The structure contains four metal cation sites, two Sb (Sb1 dominated by Pb2+) and two Ni (with minor Co2+ content) sites. The close similarity in metrics between hrabákite and tučekite is due to similar bond lengths of Pb–S and Sb–S pairs. Hrabákite is named after Josef Hrabák, the former professor of the Příbram Mining College.

Bicapite, KNa2Mg2(H2PV145+O42)·25H2O, a new polyoxometalate mineral with a bicapped Keggin anion from the Pickett Corral mine, Montrose County, Colorado, U.S.A.

2019 ◽  
Vol 104 (12) ◽  
pp. 1851-1856 ◽  
Author(s):  
Anthony R. Kampf ◽  
John M. Hughes ◽  
Barbara P. Nash ◽  
Joe Marty
Keyword(s):  
Crystal Structure ◽  
Electron Probe ◽  
Structural Unit ◽  
New Mineral ◽  
Charge Balance ◽  
Keggin Anion ◽  
Naturally Occurring ◽  
New Mineral Species ◽  
Mohs Hardness ◽  
Measured Density

Abstract Bicapite, KNa2Mg2(H2PV145+O42)·25H2O, is a new mineral species (IMA2018-048) discovered at the Pickett Corral mine, Montrose County, Colorado, U.S.A. Bicapite occurs as square tablets up to about 0.2 mm on edge on montroseite-corvusite-bearing sandstone. Crystals are dark red-brown, often appearing black. The streak is orange, and the luster is vitreous. Bicapite is brittle, has a Mohs hardness of 1½, and displays one excellent cleavage on {100}. The measured density is 2.44(2) g/cm3. Bicapite is uniaxial (+), ω = 1.785(5), ε ≈ 1.81 (white light); pleochroism is red-brown; E &gt; O, slight. The electron probe microanalysis and results of the crystal structure determination provided the empirical formula (based on 67 O apfu) (K1.23Na2.23Mg1.48)Σ4.94[H2.51P1.02(V13.915+Mo0.076+)Σ13.98O42]·25H2O. Bicapite is tetragonal, I4/m, with a = 11.5446(12) Å, c = 20.5460(14) Å, V = 2738.3(6) Å3, and Z = 2. The strongest four lines in the diffraction pattern are [d in Å (I) (hkl)]: 10.14 (100) (002,101); 2.978 (29) (134,206); 2.809 (11) (305); and 2.583 (11) (420,008). The atomic arrangement of bicapite was solved and refined to R1 = 0.0465 for 1008 independent reflections with I &gt; 2σI. The structural unit is a [H2PV125+O40(V5+O)2]7– heteropolyanion composed of 12 distorted VO6 octahedra surrounding a central PO4 tetrahedron and capped on opposite sides by two VO5 square pyramids; the structural unit is a modification of the α-isomer of the Keggin anion, [XM12O40]n–. Charge balance in the structure is maintained by the [KNa2Mg2(H2O)25]7+ interstitial complex. The name bicapite is in recognition of this being the only known mineral with a structure based on a bicapped Keggin anion. The discovery of bicapite and numerous other natural polyoxometalate compounds in the Colorado Plateau uranium/vanadium deposits make that the most productive region found to date for naturally occurring polyoxometalate compounds.

Badakhshanite-(Y), Y2Mn4Al(Si2B7BeO24), a new mineral species of the perettiite group from a granite miarolic pegmatite in Eastern Pamir, the Gorno Badakhshan Autonomous Oblast, Tajikistan

2020 ◽  
Vol 58 (3) ◽  
pp. 381-394
Author(s):  
Leonid A. Pautov ◽  
Mirak A. Mirakov ◽  
Fernando Cámara ◽  
Elena Sokolova ◽  
Frank C. Hawthorne ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Close Association ◽  
Coarse Grained ◽  
New Mineral ◽  
Orthorhombic Space Group ◽  
Calculated Density ◽  
Conchoidal Fracture ◽  
New Mineral Species ◽  
Mohs Hardness ◽  
Cation Sites

ABSTRACT Badakhshanite-(Y), ideally Y2Mn4Al(Si2B7BeO24), is a tetrahedral sheet-structure mineral found in the Dorozhny (Road) miarolitic granitic pegmatite within the Kukurt pegmatite field 45 km E of Murghab, Eastern Pamir, Gorno-Badakhshan Autonomous Oblast, Tajikistan. Badakhshanite-(Y) occurs in medium- to coarse-grained non-graphic albite-microcline-quartz pegmatites in close association with smoky quartz, Sc-bearing spessartine, Sc-bearing tusionite, and schorl. It often grows together with Sc-bearing tusionite and occurs as single columnar crystals ranging from 50 to 400 μm in length, as inclusions in spessartine and tourmaline, and rarely as crystals in blebs along boundaries between garnet, tourmaline, and quartz. Badakhshanite-(Y) is yellow brown and has a white streak and a vitreous luster. It is brittle, with a conchoidal fracture, Mohs hardness of 6.5–7, and calculated density of 4.41 g/cm. In thin section it is transparent and pale yellow, non-pleochroic, biaxial (–), with α = 1.805(2), βcalc = 1.827, γ = 1.835(3) (λ = 590 nm); 2V (meas.) = –60(10)°. Dispersion is weak, r &gt; v. Extinction is straight, elongation is negative. FTIR spectra show the absence of (OH) and H2O groups. Chemical analysis by electron microprobe using WDS (6 points), SIMS, and ICP-OES for B and Be gave SiO2 11.96, ThO2 0.12, Sm2O3 0.17, Gd2O3 0.30, Tb2O3 0.10, Dy2O3 0.73, Ho2O3 0.19, Er2O3 1.34, Tm2O3 0.54, Yb2O3 8.82, Lu2O3 2.32, Y2O3 16.60, Sc2O3 1.57, Al2O3 3.06, B2O3 22.06, FeO 0.94, MnO 23.33, CaO 0.58, BeO 2.84, total 97.57 wt.%.The empirical formula based on 24 O apfu is (Y1.21REE0.78Th0.01)Σ2(Mn3.47Y0.34Ca0.11Fe2+0.08)Σ4(Al0.63Sc0.24Fe2+0.06□0.07)Σ1[(Si2.10B6.69Be1.20)Σ9.99O24], where REE = (Yb0.47Lu0.12Dy0.04Er0.07Tm0.03 Ho0.01Gd0.02Sm0.01Tb0.01)Σ0.78. Badakhshanite-(Y) is orthorhombic, space group Pnma, a 12.852(1), b 4.5848(5), c 12.8539(8) Å, V 757.38(7) Å3, Z = 2. The crystal structure was refined to R1 = 4.31% based on 1431 unique [F &gt; 4σF] reflections. In the crystal structure of badakhshanite-(Y), a layer of tetrahedra parallel to (010) is composed of four different tetrahedrally coordinated sites: Si, B(1), B(2), and T (&lt;Si–O&gt; = 1.623 Å, &lt;B(1)–O&gt; = 1.485 Å, &lt;B(2)–O&gt; = 1.479 Å, &lt;T–O&gt; = 1.557 Å), which form four-, five-, and eight-membered rings, having the composition (Si2B7BeO24). Between the sheets of tetrahedra, there are three cation sites: M(1), M(2), and M(3) (&lt;M(1)–O&gt; = 2.346 Å, &lt;M(2)–O&gt; = 2.356 Å, &lt;M(3)–O&gt; = 2.016 Å) occupied by Y(REE), Mn2+(Y, Ca, Fe2+), and Al(Sc), respectively. The M(1,2) sites ideally give Y2Mn4apfu; the M(3) site ideally gives Al apfu. Badakhshanite-(Y) is an Al- and Be-analogue of perettiite-(Y).

Barikaite, Pb10Ag3(Sb8As11)Σ19S40, a new member of the sartorite homologous series

2013 ◽  
Vol 77 (7) ◽  
pp. 3039-3046 ◽  
Author(s):  
D. Topa ◽  
E. Makovicky ◽  
H. Tajedin ◽  
H. Putz ◽  
G. Zagler
Keyword(s):  
Homologous Series ◽  
Empirical Formula ◽  
Mean Value ◽  
Crystal Structure Analysis ◽  
New Mineral ◽  
Calculated Density ◽  
Cell Parameters ◽  
New Mineral Species ◽  
Reflected Light ◽  
Mohs Hardness

AbstractBarikaite, ideally Pb10Ag3(Sb8As11)Σ19S40, is a new mineral species from the Barika Au-Ag deposit, Azarbaijan Province, western Iran. It was formed in fractures developed in silica bands situated in massive banded pyrite and baryte ores. These fractures house veinlets that contain a number of Ag-As-Sb-Pb-rich sulfosalts, tetrahedrite-tennantite, realgar, pyrite and electrum. Barikaite appears as inclusions in guettardite. The mineral is opaque, greyish black with a metallic lustre; it is brittle without any discernible cleavage. In reflected light barikaite is greyish white, pleochroism is distinct, white to dark grey. Internal reflections are absent. In crossed polars, anisotropism is distinct with rotation tints in shades of grey. The reflectance data (%, in air) are: 37.0, 39.3 at 470 nm, 34.1, 36.9 at 546 nm, 33.1, 36.2 at 589 nm and 31.3, 34.1 at 650 nm. The Mohs hardness is 3–3½, microhardness VHN50 exhibits the range 192 – 212, with a mean value of 200 kg mm–2. The average results of five electron-microprobe analyses in a grain are (in wt.%): Pb 35.77(33), Ag 5.8(1), Tl 0.15(08), Sb 18.33(09), As 15.64(16), S 24.00(15), total 99.69(10) wt.%, corresponding to Pb9.31Ag2.90Tl0.04(Sb8.12As11.26)Σ19.36S40.37 (on the basis of 32Me + 40S = 72 a.p.f.u.). The simplified formula, Pb10Ag3(Sb8As11)Σ19S40, is in accordance with the results of a crystal-structure analysis, and requires Pb 37.89, Ag 5.91, Sb 17.79, As 15.05 and S 23.42 (wt.%). The variation of chemical composition is minor, the empirical formula ranging from Pb10.39Ag2.32Tl0.02Sb7.52As11.27S40.49 to Pb9.24Ag2.93Tl0.04Sb8.13As11.35S40.31. Barikaite has monoclinic symmetry, space group P21/n and unit-cell parameters a 8.5325(7) Å, b 8.0749(7) Å, c 24.828(2) Å, and b 99.077(6)o, Z = 1. Calculated density for the empirical formula is 5.34 (g cm–3). The strongest eight lines in the (calculated) powder-diffraction pattern [d in Å(I)(hkl)] are: 3.835(63)(022), 3.646(100)(016), 3.441(60)(212), 3.408(62)(14), 2.972(66)(16), 2.769(91)(222), 2.752(78)(24) and 2.133(54)(402). Barikaite is the N = 4 member of the sartorite homologous series with a near-equal role of As and Sb, which have an ordered distribution pattern in the structure. It is a close homeotype of rathite and more distantly related to dufrénoysite (both distinct, pure arsenian N = 4 members) and it completes the spectrum of Sb-rich members of the sartorite homologous series. The new mineral and its name have been approved by the IMA-CNMNC (IMA 2012-055).

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