Structural, chemical and spectroscopic re-examination of type uklonskovite leads to its redefinition

2017 ◽  
Vol 81 (6) ◽  
pp. 1397-1404 ◽  
Author(s):  
S. Menchetti ◽  
L. Bindi ◽  
D. Belakovskiy ◽  
F. Zaccarini
Keyword(s):  
Crystal Structure ◽  
Scientific Literature ◽  
Careful Analysis ◽  
Chemical Formula ◽  
International Mineralogical Association ◽  
Mineralogical Association ◽  
Structural Details ◽  
First Time ◽  
Shed Light

AbstractThe crystal structure and the chemical composition of uklonskovite from the holotype material was reinvestigated to shed light on its correct chemical formula. On the basis of information gained from this characterization, we revised the formula from NaMg(SO4)OH·2H2O to NaMg(SO4)F·2H2O (F instead of OH). A careful analysis of the structural details together with a critical review of all the chemical data listed in the scientific literature for uklonskovite support our redefinition. We also present Raman data for the mineral for the first time. Our proposal was approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (voting proposal 16-J).

scholarly journals Spiridonovite, (Cu1-xAgx)2Te (x ≈ 0.4), a New Telluride from the Good Hope Mine, Vulcan, Colorado (U.S.A.)

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 194
Author(s):  
Marta Morana ◽  
Luca Bindi
Keyword(s):  
Crystal Structure ◽  
Vickers Hardness ◽  
Maximum Size ◽  
Unit Cell ◽  
New Mineral ◽  
Unit Cell Parameters ◽  
International Mineralogical Association ◽  
Cell Parameters ◽  
Mineralogical Association

Here we describe a new mineral in the Cu-Ag-Te system, spiridonovite. The specimen was discovered in a fragment from the cameronite [ideally, Cu5-x(Cu,Ag)3+xTe10] holotype material from the Good Hope mine, Vulcan, Colorado (U.S.A.). It occurs as black grains of subhedral to anhedral morphology, with a maximum size up to 65 μm, and shows black streaks. No cleavage is observed and the Vickers hardness (VHN100) is 158 kg·mm-2. Reflectance percentages in air for Rmin and Rmax are 38.1, 38.9 (471.1 nm), 36.5, 37.3 (548.3 nm), 35.8, 36.5 (586.6 nm), 34.7, 35.4 (652.3 nm). Spiridonovite has formula (Cu1.24Ag0.75)Σ1.99Te1.01, ideally (Cu1-xAgx)2Te (x ≈ 0.4). The mineral is trigonal and belongs to the space group P-3c1, with the following unit-cell parameters: a = 4.630(2) Å, c = 22.551(9) Å, V = 418.7(4) Å 3, and Z = 6. The crystal structure has been solved and refined to R1 = 0.0256. It can be described as a rhombohedrally-compressed antifluorite structure, with a rough ccp arrangement of Te atoms. It consists of two Te sites and three M (metal) sites, occupied by Cu and Ag, and is characterized by the presence of edge-sharing tetrahedra, where the four-fold coordinated M atoms lie. The mineral and its name have been approved by the Commission of New Minerals, Nomenclature and Classification of the International Mineralogical Association (No. 2018-136).

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.

scholarly journals The crystal structure of cesbronite, Cu3TeO4(OH)4: a novel sheet tellurate topology

2018 ◽  
Vol 74 (1) ◽  
pp. 24-31 ◽  
Author(s):  
O. P. Missen ◽  
S. J. Mills ◽  
M. D. Welch ◽  
J. Spratt ◽  
M. S. Rumsey ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Bond Valence ◽  
Chemical Formula ◽  
Charge Balance ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
International Mineralogical Association ◽  
Average Structure ◽  
Bond Valence Analysis

The crystal structure of cesbronite has been determined using single-crystal X-ray diffraction and supported by electron-microprobe analysis, powder diffraction and Raman spectroscopy. Cesbronite is orthorhombic, space group Cmcm, with a = 2.93172 (16), b = 11.8414 (6), c = 8.6047 (4) Å and V = 298.72 (3) Å3. The chemical formula of cesbronite has been revised to CuII 3TeVIO4(OH)4 from CuII 5(TeIVO3)2(OH)6·2H2O. This change has been accepted by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association, Proposal 17-C. The previously reported oxidation state of tellurium has been shown to be incorrect; the crystal structure, bond valence studies and charge balance clearly show tellurium to be hexavalent. The crystal structure of cesbronite is formed from corrugated sheets of edge-sharing CuO6 and (Cu0.5Te0.5)O6 octahedra. The structure determined here is an average structure that has underlying ordering of Cu and Te at one of the two metal sites, designated as M, which has an occupancy Cu0.5Te0.5. This averaging probably arises from an absence of correlation between adjacent polyhedral sheets, as there are two different hydrogen-bonding configurations linking sheets that are related by a ½a offset. Randomised stacking of these two configurations results in the superposition of Cu and Te and leads to the Cu0.5Te0.5 occupancy of the M site in the average structure. Bond-valence analysis is used to choose the most probable Cu/Te ordering scheme and also to identify protonation sites (OH). The chosen ordering scheme and its associated OH sites are shown to be consistent with the revised chemical formula.

Classification of the minerals of the graftonite group

2018 ◽  
Vol 82 (6) ◽  
pp. 1301-1306 ◽  
Author(s):  
Frank C. Hawthorne ◽  
Adam Pieczka
Keyword(s):  
Crystal Structures ◽  
Distinct Species ◽  
International Mineralogical Association ◽  
Coordination Numbers ◽  
Mineralogical Association ◽  
Strong Order

ABSTRACTA classification and nomenclature scheme has been approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification for the minerals of the graftonite group. The crystal structures of these minerals have three distinct sites that are occupied by Fe2+, Mn2+and Ca2+. These sites have coordination numbers [8], [5] and [6], and these differences lead to very strong order of Fe2+, Mn2+and Ca2+over these sites. As a result of this strong order, the following compositions have been identified as distinct species: graftonite: FeFe2(PO4)2; graftonite-(Ca): CaFe2(PO4)2; graftonite-(Mn): MnFe2(PO4)2; beusite: MnMn2(PO4)2; and beusite-(Ca): CaMn2(PO4)2.

Crystal chemistry and nomenclature of rhodonite-group minerals

2019 ◽  
Vol 83 (6) ◽  
pp. 829-835 ◽  
Author(s):  
Nadezhda V. Shchipalkina ◽  
Igor V. Pekov ◽  
Nikita V. Chukanov ◽  
Cristian Biagioni ◽  
Marco Pasero
Keyword(s):  
Crystal Chemistry ◽  
Structural Formula ◽  
Structure Type ◽  
Mineral Species ◽  
Triclinic Space Group ◽  
Space Group ◽  
International Mineralogical Association ◽  
Mineralogical Association ◽  
General Chemical

AbstractThis paper presents the nomenclature of the rhodonite group accepted by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA). An overview of the previous studies of triclinic (space group P$\bar{1}$) pyroxenoids belonging to the rhodonite structure type, with a focus on their crystal chemistry, is given. These minerals have the general structural formula VIIM(5)VIM(1)VIM(2)VIM(3)VIM(4)[Si5O15]. The following dominant cations at the M sites are known at present: M(5) = Ca or Mn2+, M(1–3) = Mn2+; and M(4) = Mn2+ or Fe2+. In accordance with the nomenclature, the rhodonite group consists of three IMA-approved mineral species having the following the general chemical formulae: M(5)AM(1–3)B3M(4)C[Si5O15], where A = Ca or Mn2+; B = Mn2+; and C = Mn2+ or Fe2+. The end-member formulae of approved rhodonite-group minerals are as follows: rhodonite CaMn3Mn[Si5O15]; ferrorhodonite CaMn3Fe[Si5O15]; and vittinkiite MnMn3Mn[Si5O15].

The crystal-structure determination and redefinition of eztlite, Pb22+ Fe33+(Te4+O3)3(SO4)O2Cl

2018 ◽  
Vol 82 (6) ◽  
pp. 1355-1367 ◽  
Author(s):  
Owen P. Missen ◽  
Stuart J. Mills ◽  
John Spratt ◽  
Mark D. Welch ◽  
William D. Birch ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Mixed Valence ◽  
Lone Pair ◽  
Water Molecules ◽  
Monoclinic Space Group ◽  
Charge Balance ◽  
X Ray Diffraction ◽  
International Mineralogical Association ◽  
Bond Valence Analysis

ABSTRACTThe crystal structure of eztlite has been determined using single-crystal synchrotron X-ray diffraction and supported using electron microprobe analysis and powder diffraction. Eztlite, a secondary tellurium mineral from the Moctezuma mine, Mexico, is monoclinic, space group Cm, with a = 11.466(2) Å, b = 19.775(4) Å, c = 10.497(2) Å, β = 102.62(3)° and V = 2322.6(9) Å3. The chemical formula of eztlite has been revised to ${\rm Pb}_{\rm 2}^{2 +} {\rm Fe}_3^{3 +} $(Te4+O3)3(SO4)O2Cl from that stated previously as ${\rm Fe}_6^{3 +} {\rm Pb}_{\rm 2}^{2 +} $(Te4+O3)3(Te6+O6)(OH)10·nH2O. This change has been accepted by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association, Proposal 18-A. Eztlite was reported originally to be a mixed-valence Te oxysalt; however the crystal structure, bond-valence analysis and charge balance considerations clearly show that all Te is tetravalent. Eztlite contains a unique combination of elements and is only the second Te oxysalt to contain both sulfate and chloride. The crystal structure of eztlite contains mitridatite-like layers, with a repeating triangular nonameric [${\rm Fe}_9^{3 +} $O36]45– arrangement formed by nine edge-sharing Fe3+O6 octahedra, decorated by four trigonal pyramidal Te4+O3 groups, compared to PO4 or AsO4 tetrahedra in mitridatite-type minerals. In eztlite, all four tellurite groups associated with one nonamer are orientated with the lone pair of the Te atoms pointing in the same direction, whereas in mitridatite the central tetrahedron is orientated in the opposite direction to the others. In mitridatite-type structures, interlayer connections are formed exclusively via Ca2+ and water molecules, whereas the eztlite interlayer contains Pb2+, sulfate tetrahedra and Cl–. Interlayer connectivity in eztlite is achieved primarily by connections via the long bonds of Pbφ8 and Pbφ9 groups to sulfate tetrahedra and to Cl–. Secondary connectivity is via Te–O and Te–Cl bonds.

scholarly journals Raman Spectroscopy and Single-Crystal High-Temperature Investigations of Bentorite, Ca6Cr2(SO4)3(OH)12·26H2O

Minerals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 38
Author(s):  
Rafał Juroszek ◽  
Biljana Krüger ◽  
Irina Galuskina ◽  
Hannes Krüger ◽  
Martina Tribus ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Single Crystal ◽  
Chemical Formula ◽  
Crystal Chemical Formula ◽  
Single Crystal Diffraction ◽  
Bending Vibrations ◽  
X Ray ◽  
First Time

The crystal structure of bentorite, ideally Ca6Cr2(SO4)3(OH)12·26H2O, a Cr3+ analogue of ettringite, is for the first time investigated using X-ray single crystal diffraction. Bentorite crystals of suitable quality were found in the Arad Stone Quarry within the pyrometamorphic rock of the Hatrurim Complex (Mottled Zone). The preliminary semi-quantitative data on the bentorite composition obtained by SEM-EDS show that the average Cr/(Cr + Al) ratio of this sample is >0.8. Bentorite crystallizes in space group P31c, with a = b = 11.1927(5) Å, c =21.7121(10) Å, V = 2355.60(18) Å3, and Z = 2. The crystal structure is refined, including the hydrogen atom positions, to an agreement index R1 = 3.88%. The bentorite crystal chemical formula is Ca6(Cr1.613Al0.387)Σ2[(SO4)2.750(CO3)0.499]Σ3.249(OH)11.502·~25.75H2O. The Raman spectra of bentorite from two different localities exhibit the presence of the main stretching and bending vibrations related to the sulfate group at 983 cm−1 (ν1), 1109 cm−1 (ν3), 442 cm−1 (ν2), and 601 cm−1 (ν4). Moreover, the presence of bands assigned to the symmetric Cr(OH)63− stretching mode and hydroxyl deformation vibrations of Cr–OH units at ~540 cm−1 and ~757 cm−1, respectively, may be used to distinguish between ettringite and bentorite. In situ high temperature single crystal XRD experiments show that the decomposition of bentorite starts at ca. 45 °C and that a dehydroxylation product similar to metaettringite is formed.

Tl-bearing sulfosalt from the Lengenbach quarry, Binn Valley, Switzerland: Philrothite, TlAs3S5

2014 ◽  
Vol 78 (1) ◽  
pp. 1-9 ◽  
Author(s):  
L. Bindi ◽  
F. Nestola ◽  
E. Makovicky ◽  
A. Guastoni ◽  
L. De Battisti
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Double Layers ◽  
New Mineral ◽  
Monoclinic Space Group ◽  
Electron Pairs ◽  
International Mineralogical Association ◽  
Mineralogical Association ◽  
Reflected Light ◽  
Mohs Hardness

AbstractPhilrothite, ideally TlAs3S5, is a new mineral from the Lengenbach quarry in the Binn Valley, Valais, Switzerland. It occurs as very rare crystals up to 200 mm across on realgar associated with smithite, rutile and sartorite. Philrothite is opaque with a metallic lustre and shows a dark brown streak. It is brittle; the Vickers hardness (VHN25) is 128 kg/mm2 (range: 120–137) (Mohs hardness of 3–3½). In reflected light philrothite is moderately bireflectant and weakly pleochroic from dark grey to light grey. Under crossed polars it is anisotropic with grey to bluish rotation tints. Internal reflections are absent. Reflectance percentages for the four COM wavelengths (Rmin and Rmax) are: 26.5, 28.8 (471.1 nm), 25.4, 27.2 (548.3 nm), 24.6, 26.3 (586.6 nm) and 24.0, 25.1 (652.3 nm), respectively.Philrothite is monoclinic, space group P21/c, with a = 8.013(2), b = 24.829(4), c = 11.762(3) Å, β = 132.84(2)°, V = 1715.9(7) Å3, Z = 8. It represents the N = 4 homologue of the sartorite homologous series. In the crystal structure [R1 = 0.098 for 1217 reflections with I > 2σ(I)], Tl assumes tricapped prismatic sites alternating to form columns perpendicular to the b axis. Between the zigzag walls of Tl coordination prisms, coordination pyramids of As(Sb) form diagonally-oriented double layers separated by broader interspaces which house the lone electron pairs of these elements.The eight strongest calculated powder-diffraction lines [d in Å(I/I0) (hkl)] are: 12.4145 (52) (020); 3.6768 (100) (61); 3.4535 (45) (131); 3.0150 (46) (53); 2.8941 (52) (81); 2.7685 (76) (230); 2.7642 (77) (34); 2.3239 (52) (092). A mean of five electron microprobe analyses gave Tl 26.28(12), Pb 6.69(8), Ag 2.50(4), Cu 0.04(2), Hg 0.07(2), As 32.50(13), Sb 3.15(3), S 26.35(10), total 97.58 wt.%, corresponding, on the basis of a total of nine atoms, to (Tl0.789Pb0.198)∑=0.987 (As2.662Sb0.159Ag0.142Cu0.004Hg0.002)∑=2.969S5.044. The new mineral has been approved by the Commission on New Minerals, Nomenclature and Classification (CNMNC) of the International Mineralogical Association (2013-066) and named for Philippe Roth (b. 1963), geophysicist and well known mineral expert on the Lengenbach minerals for more than 25 years.

Coquandite, Sb6+xO8+x(SO4)(OH)x·(H2O)1–x (x = 0.3), from the Cetine mine, Tuscany, Italy: crystal structure and revision of the chemical formula

2014 ◽  
Vol 78 (4) ◽  
pp. 871-888
Author(s):  
L. Bindi ◽  
C. Biagioni ◽  
L. Ceccantini ◽  
M. Batoni ◽  
S. Menchetti
Keyword(s):  
Crystal Structure ◽  
Scientific Literature ◽  
Crystal Chemical ◽  
Anisotropic Model ◽  
Chemical Formula ◽  
Crystal Chemical Formula ◽  
Form Complex ◽  
Triclinic Space Group ◽  
Bonding System ◽  
Sulfate Hydrate

AbstractThe crystal structure of the mineral coquandite, a rare Sb oxy-sulfate hydrate, was solved using intensity data collected from a crystal from the Cetine mine, Tuscany, Italy. This study revealed that the structure is triclinic, space group P, with a = 11.4292(5), b = 29.772(1), c = 11.2989(5) Å, α = 91.152(3), β = 119.266(4), γ = 92.624(3)° and V = 3346.4(2) Å3. The refinement of an anisotropic model led to an R index of 0.0347 for 21,061 independent reflections. Thirty-two Sb sites, five S sites and 67 oxygen sites occur in the crystal structure of coquandite. Sb atoms display the characteristic SbO3E and SbO4E coordinations whereas S fills (SO4) tetrahedral groups. These atoms are arranged in five symmetry-independent layers perpendicular to b*. Four of them and their centrosymmetrical counterparts form complex modules stacked along b* and bonded through two Sb atoms and H bonds. The complex H bonding system in the structure is discussed. On the basis of information gained from this characterization, the crystal-chemical formula was revised according to the structural results, yielding Sb6+xO8+x(SO4)(OH)x·(H2O)1–x (Z = 10) with x = 0.3 instead of Sb6O8(SO4)·H2O (Z = 12) as reported previously. A recalculation of the chemical data listed in the scientific literature for coquandite according to the structural results obtained here leads to a satisfactory agreement.

Mesaite, (V2O7)3·12H2O, a new vanadate mineral from the Packrat mine, near Gateway, Mesa County, Colorado, USA

2017 ◽  
Vol 81 (2) ◽  
pp. 319-327 ◽  
Author(s):  
Anthony R. Kampf ◽  
Barbara P. Nash ◽  
Joe Marty ◽  
John M. Hughes
Keyword(s):  
Powder Diffraction ◽  
New Mineral ◽  
Formula Unit ◽  
International Mineralogical Association ◽  
Mineralogical Association ◽  
Interlayer Region ◽  
Perfect Cleavage ◽  
Mohs Hardness ◽  
Measured Density

AbstractMesaite (IMA2015-069), ideally (V2O7)3·12H2O, is a new mineral from the Packrat mine, Gateway district, Mesa County, Colorado, USA. Crystals of mesaite occur as orangish red blades up to 0.1 mm long and ∼10 μm thick. The streak is light pinkish orange and the lustre is vitreous, transparent. Mesaite has a brittle tenacity, {010} perfect cleavage; fracture is irregular, and no parting was observed. The mineral has a Mohs hardness ≈ 2. The measured density of mesaite is 2.74(1) g cm–3. Mesaite is biaxial (–), α = 1.760(calc), β = 1.780(5), γ = 1.795(5) in white light; the measured 2V value = 81(2)°. Dispersion is strong, r < v, and pleochroism is present in shades of brownish orange. Mesaite is monoclinic, P2/n, with a = 9.146(2), b = 10.424(3), c = 15.532(4) Å, β = 102.653(7)° and V = 1444.7(6) Å3. The strongest four diffraction lines in the powder diffraction pattern are [(dobs in Å, (Iobs), (hkl)]: 10.47 (100) (010), 2.881 (25) (132, 3̄12, 033, 310), 3.568 (24) (1̄14, 1̄23, 2̄13), 3.067 (17) (1̄24, 1̄32, 2̄23). The composition of mesaite was determined by electron microprobe, and yielded an empirical formula of Mn5.32Ca0.56Zn0.31V5.96As0.04O33H23.61 on the basis of 33 O atoms per formula unit (apfu).The atomic arrangement of mesaite was solved and refined to R1 = 0.0600. The structure is formed of zigzag octahedral chains of edge-sharing Mn2+O6 octahedra. Oxygen atoms of the octahedra are shared with V2O7 groups, which link with adjacent octahedral chains to form {010} heteropolyhedral layers. The interlayer region contains Ca atoms and H2O groups. Each Ca bonds to two O6 atoms in the heteropolyhedral layer and to two fully occupied and six partially occupied O (H2O) sites in the interlayer, resulting in an effective Ca coordination of approximately seven. Similar zigzag chains of edge-sharing MnO6 octahedra decorated with V2O7 groups are also found in the mineral fianelite. Mesaite has beenapproved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA2015-069). The name mesaite is conferred for Mesa County, Colorado, USA.

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