X-ray Powder Reflections Research Articles

Potassic-magnesio-arfvedsonite, KNa2(MgFe2+Fe3+)5Si8O22(OH)2: mineral description and crystal chemistry

AbstractThe complete mineral description of potassic-magnesio-arfvedsonite, a recently approved (IMA2016-083) new species of the amphibole supergroup is provided using electron microprobe analysis (EMPA), laser ablation inductively coupled plasma mass spectrometry, single-crystal structure refinement, Mössbauer and Raman spectroscopy, as well as measurement of optical and physical properties. The holotype material was found in syenitic and granitic dyke rocks in association with quartz, potassium feldspar and aegirine–augite from the Buhovo–Seslavtsi pluton, Bulgaria. Potassic-magnesio-arfvedsonite is monoclinic C2/m, with unit-cell parameters: a = 9.9804(11), b = 18.0127(19), c = 5.2971(6) Å, β = 104.341(2)° and V = 922.61 Å3. In transmitted plane-polarised light (λ = 590 cm–1), potassic-magnesio-arfvedsonite is pleochroic: X = yellow pale-green, Y = green and Z = dark-violet brown. It is biaxial (–), α = 1.645(2), β = 1.655(2), γ = 1.660(2) and 2Vmeas. = 60° and 2Vcalc. = 70°. The empirical unit formula obtained from EMPA and structure refinement is A(K0.86Na0.0.08)0.94B(Na1.74Ca0.25 Mn2+0.01)2.00C(Mg2.67Fe2+1.42Fe3+0.76Ti0.12Mn2+0.03)5.00TSi8O22W(OH1.58F0.22O0.20)2.00. The Fe3+/Fetot ratio (0.35) is consistent with both the Mössbauer spectra and the single-crystal structure refinement. The 10 strongest X-ray powder reflections [d values (in A°), I, (hkl)] are: 8.519, 80.5, (110); 3.402, 67.3, (131); 3.295, 41.0, (240); 3.173, 65.0, (310); 2.752, 35.6, ($\bar{3}$31); 2.715, 100.0 (151); 2.591, 44.1, (061); 2.542, 73.2, ($\bar{2}$02); 2.348, 38.5, ($\bar{3}$51); 2.174, 42.0, (261). Potassic-magnesio-arfvedsonite is the product of strongly peralkaline and potassic (perpotassic) magma compositions. Trace-element analysis shows that this amphibole did not exert significant control on trace-element distribution in the crystallising peralkaline magma.

Discovery of low aluminium nevadaite from the Kara-Chagyr Area, Kyrgyzstan

The rare phosphate—nevadaite has been found at Kara-Chagyr (Batken region, Kyrgyzstan) in a zone of alteration of vanadium bearing “black shales”. It occurs as blue crusts of spherulitic aggregates of tiny tabular crystals (0.1–10 μm). It is associated with metahewettite, hummerite, carnotite, minyulite, fluellite, crandallite, variscite, and woodhouseite. Optical properties: n = 1.542–1.555, D meas (for aggregates) = 2.58(1) g/cm3, D calc = 2.582 g/cm3. The most intense X-ray powder reflections are as follows: [d/n, A, (I meas), (hkl)]: 9.54 (80) (020), 6.03 (100) (200), 5.61 (100) (130), 3.91 (60) (310), 3.41 (80) (041), 2.982 (100) (241), 2.804 (60) (331), 2.672 (70) (061), 1.845 (60) (352) 1.507 (70) (243). Calculated cell dimensions are: a = 12.072(10) A, b = 18.958(15) A, c = 4.969(5) A, α = β = γ = 90°, V = 1137.2 A3. Electron microprobe analyses gives (wt %): (observed (average of 8 analyses); (calculated for 22H2O)): P2O5 34.69 (31.85), SiO2 0.25 (0.24), Al2O3 25.61 (23.50), V2O 5.58 (5.13), Fe2O3 0.48 (0.46), MnO 0.03 (0.03), CuO 10.79 (9.90), ZnO 0.69 (0.65), CaO 0.18 (0.15), MgO 0.17 (0.17), K2O 0.08 (0.08), F 7.40 (6.79), H2O 17.16 (by diff.) (23.90), −F2 =O $$ \bar 3 $$ .11 ( $$ \bar 2 $$ .86), total 100.00 (100.00).The crystal-chemical formula of the mineral is (Cu 2.2 +2 □2.03V 1.21 +3 Al0.15Zn0.14Fe0.10Mg0.07Ca0.05K0.03Mn0.01)6.00(Al8.00(P7.93Si0.07O32)F6.32(OH)2.98 · 22(H2O) for the ideal number of water molecules. Nevadaite from Kara-Chagyr differs from that from the type locality, Gold Quarry (Nev., USA), by its lower Al content. The IR-spectrum, and microphotographs of nevadaite and associated minerals are given.

Superconductivity in La-doped Bi “2201”

La 3+ substitution into the Bi 2201 structure, of the “ideal” composition Bi 2Sr 2CuO δ, has been investigated by means of an extensive phase diagram study into the solid solution formation at 885°C in air. Single phase solid solutions may be presented by the formula Bi 2+ x Sr 2- x- y La y CuO δ, where y has a maximum value of 0.6. With increasing La content, the crystal symmetry changes from orthorhombic to tetragonal and the incommensurate supercell becomes less pronounced, as indicated by a decrease in intensity of the supercell X-ray powder reflections. Superconducting T conset values vary systematically with cation contents x,y and oxygen content δ; a maximum T c of 36.5 K is observed for composition x=-0.05, y=0.4.

Studies of Distortion in Potassium Manganese Fluoride, KMnF3, at 10°K: an Example of Powder Profile Analysis Using the Pearson Type VII Distribution

AbstractPearson VII functions, some of the most useful descriptions of the intensity distribution within the X-ray powder reflection, have been used to study distortion in the perovskite-type structure of KMnF3. Separate full-widths, Δ, at half-maximum intensity, and Pearson exponents, m, were taken for the low- and high-angle sides of the profiles. The background was assumed to be linear. For the distorted structure, summation was made over all overlapping lines that might possibly contribute to the observed profile. Measurements were performed using a powder diffractometer with a specially adapted electronic system consisting of an automatic data recorder and a method, developed at this laboratory, for transferring data to an IBM PC/AT computer. By these means it could be shown that at 10° K the crystal structure of KMnF3distorts from cubic to monoclinic.

A program for the calculation of the positions of X-ray powder reflections

A novel heteronuclear Salen complex, [NiHgCl2(L)] (1) (H2L = N,N′-bis(3-methoxysalicylidene)-2,2-dimethylpropane-1,3-diamine) has been integrated using two different synthetic lines. The complex is characterized by various spectroscopic techniques, matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), and single-crystal X-ray diffraction (SC-XRD). Powder X-ray diffraction (PXRD) confirms complex phase purity and crystallinity. The scanning electron microscope and energy-dispersive X-ray analysis (SEM-EDX) identified the element’s chemical composition, morphology, and crystal size. X-ray diffraction revealed ligand released phenoxide-type deprotonated form [L]2− and had spent two pockets, N2O2 pocket occupied by Ni(II) comprises square planar geometry (NiN2O2). In contrast, Hg(II) occupies a large open O4 compartment accompanied by two chloride ions (HgO4Cl2), switching to achieve a trigonal prismatic structure. The close surveillance of the crystal structure discloses various non-covalent interactions like H-bonding, CH⋯π, and π⋯π. The complex’s geometry was fully optimized, employing the quantum chemistry method at the DFT/B3LYP with the 6-31G (d, p) basis set to divine the vibrational spectra, NMR chemical shifts, and solvent effect on the electronic properties. Natural Bond Orbital (NBO) dissected the stability of the molecular structure and the intermolecular orbital interactions. The highest stabilizing energy was 132.84 kcal/mol between the lone pair C12 and the antibonding of N7-C17 atoms. The Hirshfeld Surface (HS) is detectable that the H⋯N input is maximum than H⋯O. The electrophilic-nucleophilic sites, non-covalent interactions, and reactivity were investigated based on Molecular Electrostatic Potential (MESP), Reduced Density Gradient (RDG), atoms in a molecule (AIM), and the HOMO-LUMO difference. Eventually, a significant correlation was anticipated between theoretical and experimental spectroscopic criteria.

Calculation of the X-ray powder reflection profiles of very small needle-like crystals. II. Quantitative results on eskisehir sepiolite fibers

A calculation method for the X-ray profiles from small, needle-like crystallites [Yücel, Rautureau, Tchoubar & Tchoubar (1980). J. Appl. Cryst. 13, 370–374] is applied to natural Eskisehir sepiolite mineral. By analysing the hk0 reflections, quantitative results are given on the average cross-sectional dimensions, their distribution, preferred directions of growth, lattice parameters, hydration state, and imperfections. Practical methods for the determination of the zeolitic water content and the importance of boundary effects are proposed.

Calculation of the X-ray powder reflection profiles of very small needle-like crystals. I. Principles of the method

The aim of this paper is to develop a calculation method which allows the theoretical profiles of X-ray powder reflections to be obtained in the case of very small needle-like crystallites. This method takes into account not only the shape transform of the crystallite but also the variation of the structure factor. The study is limited to the case where the cross section of the needles contains two of the principal crystallographic axes and the third axis is along the crystallite direction of elongation. An example of the application of this method is given for a microcrystallized fibrous silicate known as sepiolite.

Hisingerite Occurring as a Weathering Product of Iron-Rich Saponite

AbstractHisingerite occurs as a weathering product of iron-rich saponite in rhyolitic tuff of Oya, Tochigi Prefecture. The chemical composition: SiO2, 40·68%; Al2O3, 4·44%; Fe2O3, 28·54%; MgO, 1·85%; CaO, 1·42%; Na2O, 1·50%; K2O, 0·33%; H2O+, 6·43%; H2O−, 13·70%; total 98·89%. Very broad and weak X-ray powder reflections occur at 16, 4·5, 2·5, 1·7 and 1·5 Å, which correspond to the main peaks of nontronite. It is considered that trioctahedral iron-rich saponite was altered to hisingerite, a very poorly crystalline form of nontronite, by oxidation of iron and advanced leaching of octahedral Mg ions.

On Dehydration of Bound Water of Sepiolite

AbstractBound water of sepiolite dehydrates in two steps in the temperature range of 250-650°C, as shown in the TG-curve. These steps are described here as steps II and III. At step II, half of the bound water is removed; other half at step III. From step II to III, discontinuous changes are confirmed in such properties as activation energy of dehydration, a-dimension, axial ratio, and intensities and spacings of X-ray powder reflections. A structural state at step II may be recognized as a distinct phase in the dehydration process.

SUBSOLIDUS PHASE RELATIONS IN THE SYSTEM Ag–Sb

Phase relations were determined in the Ag–Sb system through the temperature range 500° to 300 °C to permit a better understanding of the origin of certain silver ores and to provide a base for the study of more complex sulfosalt systems. The Sb-rich solvus for the ε phase (Ag6 ± xSb) at 500°, 450°, 350°, and 300 °C occurs at 18.2, 17.75, 17.75, and 17.7 weight percent Sb, respectively. The Ag-rich solvus of the ε′ phase (dyscrasite) occurs at 22.5% Sb at 500 °C and 22.9% at 450°, 400°, 350°, and 300 °C. The Sb-rich solvus of this phase occurs at 27.2% Sb at 500°, 450°, 400°, and 350 °C. Therefore the atomic silver to antimony ratio ranges from nearly 4 to 3, and the formula may be written Ag7 ± xSb2. An order–disorder transition of ε′ to a third phase, ε″, reported to occur at about 440° to 449 °C, was not observed. The compositions of the solid solutions relate to high angle X-ray powder reflections through the following functions: for ε phase, d = 0.000150x + 0.79743, and for ε′ phase, d = 0.00160x + 0.76608, where d is the specific interplanar spacing in Ångstroms and x is the weight percent antimony.

Bentonite deposits at Hattari, Hokkaido (II)

The Hattari bentonite deposits which are situated at the southwestern end of the Shakotan Peninsula occur in the Miocene green tuff formation. This formation in the neighborhood of the deposits is divided into the following three zones from the lower side by kinds of zeolites in the tuff: (1) Analcime zone in the northeastern part of this mining area. (2) Non-zeolite zone in the middle part. (3) Clinoptilolite zone in the southwestern part. These zones do not always correspond with the subdivision of the strata. The bentonite deposits are found in the clinoptilolite zone and the ore bodies form irregularly lenticular beds. The original rock of the bentonite is rhyolitic vitric tuff. The main mineral compositions of the ore are montmorillonite, zeolite, α-cristobalite, opal, quartz, plagioclase and biotite. Microscopically, montmorillonite fills up the interspaces of glass fragments, and is also formed in these marginal zones. Most of zeolite, α-cristobalite and opal are probably included in glass fragments. X-ray investigation shows that bentonite in water is mechanically divided into montmorillonite group and zeolite one which is identified as clinoptilolite. The differential thermal analysis curve of the material shows no remarkable thermal peak up to 1, 000°C. X-ray powder reflections after heating at 100°C, ......, 800°C, 850°C, 900°C and 1, 000°C and effects of the treatments with HCl against the material do not completely agree with the already known data of clinoptilolite. The rate of swelling of the bentonite is related to the shape of 15_??_; peak of X-ray reflection pattern, and it decreases by repetition of swelling and drying. The cation-exchange capacity of the bentonite is 96 me/100gr. It is considered that the existence of the hydrothermal sulfides ore deposits in this mining area, the relation with the division of the strata and the zonal arrangement of zeolities, the mode of occurrence of the bentonite, and the silicification and adulariazation of the country rocks show that the Hattari bentonite deposits might be formed by a diagenesis and a hydrothermal alteration of vitric tuff.

Bentonite deposits at Hattari, Hokkaido (I)

The Hattari bentonite deposits which are situated at the southwestern end of the Shakotan Peninsula occur in the Miocene green tuff formation. This formation in the neighborhood of the deposits is divided into the following three zones from the lower side by kinds of zeolites in the tuff: (1) Analcime zone in the northeastern part of this mining area. (2) Non-zeolite zone in the middle part. (3) Clinoptilolite zone in the southwestern part. These zones do not always correspond with the subdivision of the strata. The bentonite deposits are found in the clinoptilolite zone and the ore bodies form irregularly lenticular beds. The original rock of the bentonite is rhyolitic vitric tuff. The main mineral compositions of the ore are montmorillonite, zeolite, α-cristobalite, opal, quartz, plagioclase and biotite. Microscopically, montmorillonite fills up the interspaces of glass fragments, and is also formed in these marginal zones. Most of zeolite, α-cristobalite and opal are probably included in glass fragments. X-ray investigation shows that bentonite in water is mechanically divided into montmorillonite group and zeolite one which is identified as clinoptilolite. The differential thermal analysis curve of the material shows no remarkable thermal peak up to 1, 000°C. X-ray powder reflections after heating at 100°C, ......, 800°C, 850°C, 900°C and 1, 000°C and effects of the treatments with HCl against the material do not completely agree with the already known data of clinoptilolite. The rate of swelling of the bentonite is related to the shape of 15_??_; peak of X-ray reflection pattern, and it decreases by repetition of swelling and drying. The cation-exchange capacity of the bentonite is 96 me/100gr. It is considered that the existence of the hydrothermal sulfides ore deposits in this mining area, the relation with the division of the strata and the zonal arrangement of zeolities, the mode of occurrence of the bentonite, and the silicification and adulariazation of the country rocks show that the Hattari bentonite deposits might be formed by a diagenesis and a hydrothermal alteration of vitric tuff.

X-RAY STUDY OF TRIDYMITE (3)

Four phases named S1, S2, S3 and S4 in tridymite of type S were confirmed on the close examination of the change of X-ray powder reflections with increasing temperatures.Unit cell dimensions are: S1; monoclinic, a=10.04Å, b=17.28Å, c=8.20Å, β=91.50°, S2; orthorhombic, a=10.04Å, b=17.28Å, c=8.20Å, S3; domain structure, and S4; hexagonal, a=5.046-5.06Å, c=8.236-8.30Å. Their relations are as follows, S1 → 60-75°C S2 → 115° S3 → 250°C S4. Though the change of the patterns with decreasing temperatures is not thoroughly investigated, the transition is reversible.

X-RAY STUDY OF TRIDYMITE (1)

Tridymite was synthesized under various conditions with respect to starting materials and mineralizers in room pressures. Some of them, in its X-ray powder diffraction data, show the features of tridymite M and tridymite S, which were confirmed by Hill and Roy in sythetic tridymite under the hydrothermal condition, and the others are grouped into the intermediate between M and S. As the rusults of examination of their X-ray powder reflections and their D. T. A. curves, detailed criteria for grouping the tridymites by X-ray means in the present experiments were given along with the suggestions that these differences are due to the distortion of the structure at high-low inversion.

On the Clay Showing the X-ray Powder Reflections of Tridymite

On the Clay Showing the X-ray Powder Reflections of Tridymite