scholarly journals Grammatikopoulosite, NiVP, a New Phosphide from the Chromitite of the Othrys Ophiolite, Greece

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 131 ◽  
Author(s):  
Luca Bindi ◽  
Federica Zaccarini ◽  
Elena Ifandi ◽  
Basilios Tsikouras ◽  
Chris Stanley ◽  
...  
Keyword(s):  
Empirical Formula ◽  
Polarized Light ◽  
Orthorhombic Space Group ◽  
Average Composition ◽  
International Mineralogical Association ◽  
Small Crystals ◽  
Podiform Chromitite ◽  
Of Greece ◽  
The Ideal

Grammatikopoulosite, NiVP, is a new phosphide discovered in the podiform chromitite and hosted in the mantle sequence of the Othrys ophiolite complex, central Greece. The studied samples were collected from the abandoned chromium mine of Agios Stefanos. Grammatikopoulosite forms small crystals (from 5 μm up to about 80 μm) and occurs as isolated grains. It is associated with nickelphosphide, awaruite, tsikourasite, and an undetermined V-sulphide. It is brittle and has a metallic luster. In plane-polarized light, it is creamy-yellow, weakly bireflectant, with measurable but not discernible pleochroism and slight anisotropy with indeterminate rotation tints. Internal reflections were not observed. Reflectance values of mineral in air (R1, R2 in %) are: 48.8–50.30 at 470 nm, 50.5–53.5 at 546 nm, 51.7–55.2 at 589 nm, and 53.2–57.1 at 650 nm. Five spot analyses of grammatikopoulosite give the average composition: P 19.90, S 0.41, Ni 21.81, V 20.85, Co 16.46, Mo 16.39, Fe 3.83, and Si 0.14, total 99.79 wt %. The empirical formula of grammatikopoulosite—based on Σ(V + Ni + Co + Mo + Fe + Si) = 2 apfu, and taking into account the structural results—is (Ni0.57Co0.32Fe0.11)Σ1.00(V0.63Mo0.26Co0.11)Σ1.00(P0.98S0.02)Σ1.00. The simplified formula is (Ni,Co)(V,Mo)P and the ideal formula is NiVP, which corresponds to Ni 41.74%, V 36.23%, P 22.03%, total 100 wt %. The density, calculated on the basis of the empirical formula and single-crystal data, is 7.085 g/cm3. The mineral is orthorhombic, space group Pnma, with a = 5.8893(8), b = 3.5723(4), c = 6.8146(9) Å, V = 143.37(3) Å3, and Z = 4. The mineral and its name have been approved by the Commission of New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA 2019-090). The mineral honors Tassos Grammatikopoulos, geoscientist at the SGS Canada Inc., for his contribution to the economic mineralogy and mineral deposits of Greece.

scholarly journals Tsikourasite, Mo3Ni2P1+x (x < 0.25), a New Phosphide from the Chromitite of the Othrys Ophiolite, Greece

Minerals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 248 ◽  
Author(s):  
Zaccarini ◽  
Bindi ◽  
Ifandi ◽  
Grammatikopoulos ◽  
Stanley ◽  
...  
Keyword(s):  
Empirical Formula ◽  
Polarized Light ◽  
Average Composition ◽  
Synthetic Compound ◽  
Space Group ◽  
International Mineralogical Association ◽  
Mineralogical Association ◽  
Brunei Darussalam ◽  
Podiform Chromitite

Tsikourasite, Mo3Ni2P1+x (x < 0.25), is a new phosphide discovered in a mantle-hosted podiform chromitite collected in the abandoned mine of Agios Stefanos (Othrys ophiolite), Central Greece. It forms tiny grains (from a few μm up to about 80 μm) and occurs as isolated grains or associated with other known minerals such as nickelphosphide and awaruite, and with undetermined minerals such as Ni-allabogdanite or Ni-barringerite and a V-sulphide. Tsikourasite is brittle and has a metallic luster. In plane-polarized light, tsikourasite is white yellow and it shows no bireflectance, anisotropism or pleochroism. Internal reflections were not observed, Reflectance values of tsikourasite in air (R in %) are: 55.7 at 470 nm, 56.8 at 546 nm, 57.5 at 589 nm and 58.5 at 650 nm. Five spot analyses of tsikourasite give the average composition: P 7.97, S 0.67, V 14.13, Fe 14.37, Co 7.59, Ni 23.9, and Mo 44.16, total 99.60 wt%, corresponding to the empirical formula (Mo1.778V1.071Fe0.082Co0.069)Σ3.000(Ni1.572Co0.428)Σ2.000(P0.981S0.079)Σ1.060, on the basis of Σ(Mo +V + Fe + Co + Ni) = 5 apfu and taking into account the structural results. The simplified formula is Mo3Ni2P1+x (x < 0.25). The density, which was calculated based on the empirical formula and single-crystal data, is 9.182 g/cm3. The mineral is cubic, space group F-43m, with a = 10.8215(5) Å and Z = 16. Although tsikourasite is similar in composition to those of monipite (MoNiP), polekhovskyite (MoNiP2), and the synthetic compound MoNiP2, all these phases are hexagonal and not cubic like tsikourasite. It exhibits the same structure as the cubic Mo3Ni2P1.18 compound [space group F-43m, a = 10.846(2) Å] synthesized at 1350 °C. The mineral and its name have been approved by the Commission of New Minerals, Nomenclature and Classification of the International Mineralogical Association (No. 2018-156). The mineral honors Professor Basilios Tsikouras of the Universiti Brunei Darussalam.

scholarly journals Eliopoulosite, V7S8, A New Sulfide from the Podiform Chromitite of the Othrys Ophiolite, Greece

Minerals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 245 ◽  
Author(s):  
Luca Bindi ◽  
Federica Zaccarini ◽  
Paola Bonazzi ◽  
Tassos Grammatikopoulos ◽  
Basilios Tsikouras ◽  
...  
Keyword(s):  
Empirical Formula ◽  
Mineral Exploration ◽  
Polarized Light ◽  
Structural Data ◽  
Ore Deposits ◽  
New Mineral ◽  
International Mineralogical Association ◽  
New Mineral Species ◽  
Geochemical Studies ◽  
Of Greece

The new mineral species, eliopoulosite, V7S8, was discovered in the abandoned chromium mine of Agios Stefanos of the Othrys ophiolite, located in central Greece. The investigated samples consist of massive chromitite hosted in a strongly altered mantle tectonite, and are associated with nickelphosphide, awaruite, tsikourasite, and grammatikopoulosite. Eliopoulosite is brittle and has a metallic luster. In plane-reflected polarized light, it is grayish-brown and shows no internal reflections, bireflectance, and pleochroism. It is weakly anisotropic, with colors varying from light to dark greenish. Reflectance values of mineral in air (Ro, Re’ in %) are: 34.8–35.7 at 470 nm, 38–39 at 546 nm, 40–41.3 at 589 nm, and 42.5–44.2 at 650 nm. Electron-microprobe analyses yielded a mean composition (wt.%) of: S 41.78, V 54.11, Ni 1.71, Fe 1.1, Co 0.67, and Mo 0.66, totali 100.03. On the basis of Σatoms = 15 apfu and taking into account the structural data, the empirical formula of eliopoulosite is (V6.55Ni0.19Fe0.12Co0.07Mo0.04)Σ = 6.97S8.03. The simplified formula is (V, Ni, Fe)7S8 and the ideal formula is V7S8, which corresponds to V 58.16%, S 41.84%, total 100 wt.%. The density, based on the empirical formula and unit-cell volume refined form single-crystal structure XRD data, is 4.545 g·cm−3. The mineral is trigonal, space group P3221, with a = 6.689(3) Å, c = 17.403(6) Å, V = 674.4(5) Å3, Z = 3, and exhibits a twelve-fold superstructure (2a × 2a × 3c) of the NiAs-type subcell with V-atoms octahedrally coordinated by S atoms. The distribution of vacancies is discussed in relation to other pyrrhotite-like compounds. The mineral name is for Dr. Demetrios Eliopoulos (1947–2019), a geoscientist at the Institute of Geology and Mineral Exploration (IGME) of Greece and his widow, Prof. Maria Eliopoulos (nee Economou, 1947), University of Athens, Greece, for their contributions to the knowledge of ore deposits of Greece and to the mineralogical, petrographic, and geochemical studies of ophiolites, including the Othrys complex. The mineral and its name have been approved by the Commission of New Minerals, Nomenclature, and Classification of the International Mineralogical Association (No. 2019-96).

Palladothallite, Pd3Tl, a new mineral from the Monchetundra layered intrusion, Kola Peninsula, Russia

2021 ◽  
Vol 59 (6) ◽  
pp. 1821-1832
Author(s):  
Tatiana L. Grokhovskaya ◽  
Anna Vymazalová ◽  
František Laufek ◽  
Chris J. Stanley ◽  
Sergey Ye. Borisovskiy
Keyword(s):  
Kola Peninsula ◽  
Empirical Formula ◽  
Polarized Light ◽  
Layered Intrusion ◽  
Structure Type ◽  
New Mineral ◽  
Near Surface ◽  
Holotype Specimen ◽  
Powder Neutron Diffraction Data ◽  
The Ideal

ABSTRACT Palladothallite, Pd3Tl, is a new mineral discovered in the Monchetundra layered intrusion, Kola Peninsula, Russia. Palladothallite occurs in orthopyroxenite with disseminated Ni-Cu-Fe sulfides and in near-surface oxidized ore of an orthopyroxenite unit. In the holotype specimen, the new mineral forms anhedral grains about 1 to 20 μm in size intergrown with bortnikovite (Pt4Cu3Zn). Palladothallite and bortnikovite form a rim around tulameenite (Pt2FeCu), Pt-Pd-Fe-Cu alloys, and Pt-Pd-Fe-Cu “oxides” in a goethite matrix. In plane-polarized light, palladothallite is white, anisotropy was not observed; it exhibits no internal reflections. Reflectance values of palladothallite in air (R' in %) are: 53.9 at 470 nm, 57.1 at 546 nm, 59.4 at 589 nm and 61.7 at 650 nm. Twelve electron probe microanalyses of palladothallite gave an average composition (in wt.%): Pd 59.99, Cu 1.19, Fe 0.35, Ag 1.1, Tl 35.64, Se 0.34, and S 0.09, total 99.67, corresponding to the empirical formula (Pd2.894Cu0.096Fe0.032Ag0.053)∑3.075(Tl0.895Se0.023S0.008)∑0.926 based on four atoms, with the ideal formula Pd3Tl. The density, calculated on the basis of the empirical formula, is 13.04 g/cm3. Palladothallite crystallizes with the same structure as synthetic Pd3Tl, which was solved by Kurtzemann & Kohlmann (2010) from powder neutron diffraction data. Palladothallite is tetragonal, space group I4/mmm, with a 4.10659(9), c 15.3028(4) Å, V 258.07(1) Å3, and Z = 4. Palladothallite crystallizes in the ZrAl3 structure type. The name corresponds to its chemical composition, palladium and thallium.

Magnesio-ferri-fluoro-hornblende from Portoscuso, Sardinia, Italy: description of a newly approved member of the amphibole supergroup

2016 ◽  
Vol 80 (2) ◽  
pp. 269-275 ◽  
Author(s):  
Roberta Oberti ◽  
Massimo Boiocchi ◽  
Frank C. Hawthorne ◽  
Neil A. Ball ◽  
Luigi Chiappino
Keyword(s):  
Empirical Formula ◽  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Volcanic Rocks ◽  
Polarized Light ◽  
Monoclinic Space Group ◽  
Formula Unit ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Ideal

AbstractMagnesio-ferri-fluoro-hornblende has the ideal formula A□B Ca2C(Mg4Fe3+)T(Si7Al)O22WF2(Hawthorne et al., 2012). The holotype sample described in this work occurs as prismatic crystals in vugs of volcanic rocks (Seruci ignimbrites), found along the coast road ∼5.5 km northeast of Portoscuso, Cagliari, Sardinia; associated minerals are tridymite, todorokite, magnetite, and hematite. The name and the mineral were approved by the IMA CNMNC (2014-091). Holotype magnesio-ferri-fluoro-hornblende is monoclinic, space group C2/m, a = 9.839(5), b = 18.078(9), c = 5.319(3) Å, β = 104.99(3)°, V = 913.9(9) Å3, Z = 2. The density calculated from the empirical formula is 3.315 g cm–3. In plane-polarized light, magnesio-ferri-fluoro-hornblende is pleochroic, X = pale grey (least), Y = dark grey (most), Z = pale brownish grey (intermediate); X^a= 47.6° (β obtuse), Y // b, Z^c= 33.4° (β acute). It is biaxial negative, α = 1.669, β = 1.676, γ = 1.678, all ±0.002; 2Vobs= 74(1)°, 2Vcalc= 56°. The strongest eight lines in the powder X-ray diffraction pattern are [d in Å (I)(hkl)]: 2.711 (100)(151), 8.412 (89)(110), 3.121 (64)(310), 2.553 (61)(2̄02), 3.389 (55)(131), 2.599 (45)(061), 2.164 (36)(261), and 2.738 (34)(3̄31). Electron-microprobe analysis of the refined crystal gave SiO245.34, Al2O36.18, TiO21.22, FeO 15.24, Fe2O36.27, MgO 9.71, MnO 0.78, ZnO 0.06, CaO 10.18, Na2O 1.35, K2O 1.15, F 3.22, Cl 0.30, H2Ocalc 0.37, sum 99.95 wt.%. The empirical formula unit, calculated on the basis of 24 (O, OH, F, Cl) apfu with (OH + F + Cl) = 2 apfu is: (Na0.15K0.22)∑0.37(Na0.25Ca1.66Mn0.09)∑2.00(Mg2.20Fe2+1.94Mn0.01Zn0.01Fe3+0.72Ti0.13)∑5.01(Al1.11Si6.89)∑8.00O22[F1.55(OH)0.37Cl0.08)∑2.00.

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 &gt;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).

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 Arsenotučekite, Ni18Sb3AsS16, a new mineral from the Tsangli chromitites, Othrys ophiolite, Greece

2020 ◽  
Vol 114 (5) ◽  
pp. 435-442
Author(s):  
Federica Zaccarini ◽  
Luca Bindi ◽  
Basilios Tsikouras ◽  
Tassos Grammatikopoulos ◽  
Christopher J. Stanley ◽  
...  
Keyword(s):  
Mass Density ◽  
Polarized Light ◽  
Mantle Peridotite ◽  
New Mineral ◽  
Forming Process ◽  
International Mineralogical Association ◽  
Magmatic Sulfides ◽  
New Mineral Species ◽  
Reflected Light

Abstract Arsenotučekite, Ni18Sb3AsS16, is a new mineral discovered in the abandoned chromium mine of Tsangli, located in the eastern portion of the Othrys ophiolite complex, central Greece. Tsangli is one of the largest chromite deposit at which chromite was mined since 1870. The Tsangli chromitite occurs as lenticular and irregular bodies. The studied chromitites are hosted in a strongly serpentinized mantle peridotite. Arsenotučekite forms anhedral to subhedral grains that vary in size between 5 μm up to 100 μm, and occurs as single phase grains or is associated with pentlandite, breithauptite, gersdorffite and chlorite. It is brittle and has a metallic luster. In plane-polarized light, it is creamy-yellow, the bireflectance is barely perceptible and the pleochroism is weak. In crossed polarized reflected light, the anisotropic rotation tints vary from pale blue to brown. Internal reflections were not observed. Reflectance values of arsenotučekite in air (Ro, Re′ in %) are: 41.8–46.4 at 470 nm, 47.2–50.6 at 546 nm, 49.4–52.3 at 589 nm, and 51.3–53.2 at 650 nm. The empirical formula of arsenotučekite, based on 38 atoms per formula unit, and according to the structural results, is (Ni16.19Co1.01Fe0.83)Σ18.03Sb3(As0.67Sb0.32)Σ0.99S15.98. The mass density is 6.477 g·cm−3. The simplified chemical formula is (Ni,Co,Fe)18Sb3(As,Sb)S16. The mineral is tetragonal and belongs to space group I4/mmm, with a = 9.7856(3) Å, c = 10.7582(6) Å, V = 1030.2(6) Å3 and Z = 2. The structure is layered (stacking along the c-axis) and is dominated by three different Ni-coordination polyhedral, one octahedral and two cubic. The arsenotučekite structure can be considered as a superstructure of tučekite resulting from the ordering of Sb and As. The name of the new mineral species indicates the As-dominant of tučekite. Arsenotučekite occurs as rims partly replacing pentlandite and irregularly developed grains. Furthermore, it is locally associated with chlorite. These observations suggest that it was likely precipitated at relatively low temperatures during: 1) the late hydrothermal stages of the ore-forming process by reaction of Sb- and As-bearing solutions with magmatic sulfides such as pentlandite, or 2) during the serpentinization of the host peridotite. The mineral and its name have been approved by the Commission of New Minerals, Nomenclature, and Classification of the International Mineralogical Association (number 2019–135).

Fluoro-tremolite from the Limecrest-Southdown quarry, Sparta, New Jersey, USA: crystal chemistry of a newly approved end-member of the amphibole supergroup

2018 ◽  
Vol 82 (1) ◽  
pp. 145-157
Author(s):  
Roberta Oberti ◽  
Fernando Cámara ◽  
Fabio Bellatreccia ◽  
Francesco Radica ◽  
Antonio Gianfagna ◽  
...  
Keyword(s):  
New Jersey ◽  
Structure Refinement ◽  
X Ray ◽  
International Mineralogical Association ◽  
Holotype Specimen ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
The Ideal

ABSTRACTDuring systematic characterization of amphiboles that still lack a complete mineral description, fluoro-tremolite was identified in a specimen from the Limecrest-Southdown quarry, Sparta, New Jersey, USA, which was provided by the Franklin Mineral Museum. The ideal formula of fluoro-tremolite is A□ BCa2CMg5TSi8O22WF2 and the empirical formula derived for the holotype specimen, based on the results of electron-microprobe analysis and single-crystal structure refinement, is A(Na0.28K0.02)Σ0.30B(Ca1.99Na0.01)Σ2.00C(Mg4.70${\rm Fe}_{{\rm 0}{\rm. 28}}^{{\rm 2 +}} $Zn0.01${\rm Ti}_{{\rm 0}{\rm. 01}}^{{\rm 4 +}} $)Σ5.00T(Si7.68Al0.32)Σ8.00O22W(F1.16OH0.84)Σ2.00. The unit-cell dimensions in space group C2/m are a = 9.846(2), b = 18.050(3), c = 5.2769(14) Å, β = 104.80(2)° and V = 906.7 (3) Å3 and Z = 2; the a:b:c ratio is 0.545:1:0.292. Fluoro-tremolite is biaxial (+), with α = 1.5987(5), β = 1.6102(5), γ = 1.6257(5), 2V(meas.) = 85(1)o and 2V(calc.) = 82o. The strongest ten reflections in the powder X-ray pattern [d values (in Å), I, (hkl)] are: 2.706, 100, (151); 3.126, 67, (310); 2.531, 59, ($\bar 2$02); 3.381, 57, (131); 2.940, 43, ($\bar 1$51, 221); 3.276, 37, (240); 2.337, 36, ($\bar 3$51); 2.592, 35, (061); 2.731, 34, ($\bar 3$31); 2.163, 34, (261). Both the mineral and the mineral name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA2016–018); the holotype has been deposited at the Franklin Mineral Museum (32 Evans Street, Franklin, 07416 New Jersey, US), under the catalogue number 7710.Comparison with new data on tremolite and synthetic fluoro-tremolite provides a more sound crystal-chemical model of the end-member compositions and their solid-solution.

The crystal structure of comancheite, Hg2+55N3–24 (OH,NH2)4(Cl,Br)34, and crystal-chemical and spectroscopic discrimination of N3– and O2– anions in Hg2+ compounds

2013 ◽  
Vol 77 (8) ◽  
pp. 3217-3237 ◽  
Author(s):  
M. A. Cooper ◽  
Y. A. Abdu ◽  
F. C. Hawthorne ◽  
A. R. Kampf
Keyword(s):  
Crystal Structure ◽  
Three Dimensional ◽  
Direct Methods ◽  
Major Change ◽  
Orthorhombic Space Group ◽  
International Mineralogical Association ◽  
Mineralogical Association ◽  
Stretching Vibrations ◽  
Anion Species

AbstractThe crystal structure of comancheite, Hg2+55N3–24(OH, NH2)4(Cl,Br)34, orthorhombic, space group Pnnm, a = 18.414(5), b = 21.328(6), c = 6.6976(19) Å, V = 2630(2) Å3, Z = 1, was solved by direct methods and refined to an R1 index of 4.3% based on 4160 unique observed reflections. In the structure of comancheite, there are nine crystallographically distinct Hg2+ cations, each of which is coordinated by two N3– anions to form near-linear N3––Hg2+–N3– groups. Four other crystallographically distinct Hg2+ cations are coordinated by a mixture of N3–, O2–, (OH)– and (NH2)– anions, and there is a small amount of [Hg–Hg]2+ dimer. In addition, there are eight crystallographically distinct halogen sites, three of which are completely occupied by Cl–, and five of which are occupied by both Cl– and Br–. The principal anion, N3–, shows a strong preference for tetrahedral coordination by Hg2+, which results in a strongly bonded three-dimensional {–Hg2+–N3––} framework. This framework is both interrupted and contains large interstices that incorporate additional Hg2+ cations, a very small amount of [Hg+–Hg+]2+ dimer and additional anion species, O2–, (OH)– and (NH2)–, that coordinate Hg2+.Comancheite was described originally as an Hg-oxide mineral. The major change in chemical composition indicated by the present work was approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (Voting Proposal 13-B). The presence of N provides some analytical challenges, particularly in the presence of Hg. New bond-valence parameters were derived for Hg2+–N3– bonds [Ro(N3–) = 1.95] using well refined Hg2+ structures, and this allows discrimination between Hg2+–O2– and Hg2+–N3– bonds based on the valence-sum rule. Comparison of the Raman spectra of several Hg-bearing minerals shows that peaks in the range 500–700 cm–1 are characteristic of Hg2+–N3– stretching vibrations whereas peaks in the range 350–500 cm–1 are characteristic of Hg2+–O2– stretching vibrations; Hg2+–O2– and Hg2+ – N3– bonds may be discriminated on this basis.

Ferri-obertiite from the Rothenberg quarry, Eifel volcanic complex, Germany: mineral data and crystal chemistry of a new amphibole end-member

2017 ◽  
Vol 81 (3) ◽  
pp. 641-651 ◽  
Author(s):  
Roberta Oberti ◽  
Massimo Boiocchi ◽  
Frank C. Hawthorne ◽  
Neil A. Ball ◽  
Günter Blass
Keyword(s):  
Structure Refinement ◽  
Volcanic Complex ◽  
X Ray ◽  
International Mineralogical Association ◽  
Holotype Specimen ◽  
Cell Dimensions ◽  
Mineral Data ◽  
Unit Cell Dimensions ◽  
The Ideal

AbstractPink-orange crystals of a composition within the ferri-obertiite compositional space were found in vesicles in a pale beige silicate vein found from a basalt quarry at Mount Rothenberg, Eifel district, Germany. Associated minerals are potassic feldspar, alpha quartz paramorphic afterbeta quartz, eifelite (the second occurrence after the Caspar quarry at Bellerberg volcano, Eifel region), tridymite, rutile, roedderite and other amphiboles. The ideal formula of ferri-obertiite is ANaBNa2C(Mg3Fe3+Ti)TSi8O22WO2; the empirical formula derived for the holotype specimen from Mount Rothenberg from the results of electron-microprobe analysis and single-crystal structure refinement is A(Na0.76K0.22)∑0.98B(Na1.61Ca0.35Mn0.042+)∑2.00C(Mg3.58Mn0.112+Fe0.623+Ti0.664+Cr0.013+Zn0.01Ni0.01)∑5.00T(Si7.82Ti0.124+Al0.06)∑8.00O22W[O1.26F0.55(OH)0.19]∑2.00. The unit-cell dimensions are a = 9.7901(7), b = 17.9354(13), c = 5.2892(4)Å, β= 104.142(2)°, V = 900.58 (11) Å3. The space group is C2/m, Z = 2. Ferri-obertiite is biaxial (+), with α = 1.664, β = 1.680, γ = 1.722, all ±0.002 and 2V (meas.) = 66.4(3)o, 2V (calc.) = 64.7o.The strongest eight reflections in the powder X-ray pattern [d values (in Å), I, (hkl)] are: 2.704, 100, (151); 3.116, 76, (310); 3.388, 72, (131); 8.931, 72, (110); 2.529, 67, (202); 2.583, 39, (061); 2.160, 38, (261); 3.260, 37, (240). Both the mineral and thename have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA 2015-079); the rock specimen has been deposited at the Museo di Mineralogia, Dipartimento di Scienze della Terra e dell'Ambiente, Universitàdegli Studi di Pavia, under the code 2015-02.

Sign in / Sign up

Export Citation Format

Share Document