Irregular Aggregates Research Articles

Structure and properties of ZrO2-MgO powders

It have been studied magnesia stabilized zirconia (ZrO2-MgO) powders produced by high-frequency decomposition of water salt solutions. It have been shown that due to precursor dissociation powders consist of spherical particles with smooth surface and irregular hollow aggregates resembling foam. An increase in the magnesium concentration in the precursor has an effect on the powder properties, namely, the specific surface decreases significantly and the bulk density increases. Zirconia in the nanostructured state is present only in the powders with 8.6 and 13.9 mole% MgO, with the size of the c-ZrO2 crystallites in them no more than 100 nm. In powder with 43.3 mole% of MgO the magnesia content in c-ZrO2 solid solution corresponds to its solubility limit of 22.2 mole% at temperature 2100°C.

Self-Organization and Vesicle Formation of Amphiphilic Fulleromonodendrons Bearing Oligo(poly(ethylene oxide)) Chains.

A new series of N-methylfulleropyrrolidines bearing oligo(poly(ethylene oxide))-appended Percec monodendrons (fulleromonodendrons, 4a-f) have been synthesized. The substituted position of the oligo(poly(ethylene oxide)) chain(s) on the phenyl group of the Percec monodendron for 4a-f was varied, which is at the 4-, 2,4-, 3,5-, 3,4,5-, 2,3,4- and 2,4,6- position, respectively. 4a-e are obtained as solids at 25 °C and can self-organize into lamellar phases as revealed by X-ray diffraction (XRD) and small-angle X-ray scattering (SAXS) measurements, while 4f appears as a viscous liquid. The substitution patterns of the oligo(poly(ethylene oxide)) chain(s) also significantly influence the solubility of 4a-f, especially in ethanol and water. Formation of self-organized supramolecular structures of 4d and 4e in water as well as 4d in ethanol is evidenced from UV-vis and dynamic light scattering (DLS) measurements. Further studies in water using various imaging techniques including transmission electron microscopy (TEM), freeze-fracture TEM (FF-TEM), cryo-TEM and atomic force microscopy (AFM) observations revealed the formation of well-defined vesicles for 4d and plate-like aggregates for 4e, indicating that the aggregation behavior of the fulleromonodendrons is highly dependent on their molecular structures. For 4d in ethanol, only irregular aggregates were noticed, indicating the solvent also plays a role on regulating the aggregation behavior. After functionalization with the Percec monodendrons, 4a-f can preserve the intriguing electrochemical properties of pristine C60 as revealed by cyclic voltammetries. The thermotropic properties of 4a-f have also been investigated. It was found that all of them show good thermal stability, but no mesophases were detected within the investigated temperature ranges.

How does the anionic surfactant SDS affect the association of hydrophobically end-modified PNIPAM chains in aqueous solution?

The studies on the interaction between thermo-responsive polymer PNIPAM and various ionic surfactants have been extensively investigated in the past few years. Unfortunately, the role of the hydrophobic end-group which is inevitably introduced by the initiator or chain transfer agent was generally overlooked in related studies. In this work, to show the interplay between the hydrophobic end-group and the surfactant molecule, five n-dodecyl-terminated poly(N-isopropylacrylamide)s (PNIPAMs-C12H25) with different chain lengths were prepared by RAFT polymerization. The unambiguous molecular parameters were obtained by GPC, LLS, 1H-NMR and UV–Vis measurements. Further study on the association behaviors in SDS aqueous solutions showed that, these PNIPAM-C12H25 chains can form uniform spherical micelles accompanied with a trace amount of large irregular aggregates in pure water at 20 °C, and the size-molar mass relation of aggregates presents a scaling law. The addition of SDS could continuously weaken the association of these alkyl-terminated PNIPAMs, reflected in the decrease of average hydrodynamic radius (<Rh>) and average aggregation number (<Nagg>) of aggregates. Also, it could endow the PNIPAM chains the polyelectrolyte characteristics, reflected in the emergency of a slow relaxation mode in dynamic LLS measurement. More interestingly, the reversal of the dependence of cloud point on the chain length was observed at high SDS concentration, which may be attributed to the preferentially van der Waals interaction between the SDS dodecyl tail and the PNIPAM dodecyl chain end.

Starch-assisted synthesis and optical properties of ZnS nanoparticles

ZnS nanoparticles are fabricated via starch-assisted method. The effects of different starch amounts on structure and properties of samples are investigated, and the forming mechanism of ZnS nanoparticles is discussed. By X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible (UV–vis) spectroscopy and fluorescence (FL) spectrometer, their phases, crystalline lattice structure, morphologies, chemical and optical properties are characterized. The results show that ZnS has polycrystalline spherical structure with the mean diameter of 130nm. Sample without starch reveals irregular aggregates with particle size distribution of 0.5–2μm. The band gap value of ZnS is 3.97eV. The chemical interaction exists between starch molecules and ZnS nanoparticles by hydrogen bonds. The stronger FL emission peaks of ZnS synthesized with starch, indicate a larger content of sulfur vacancies or defects than ZnS synthesized without starch.

Temperature-Induced Aggregate Transitions in Mixtures of Cationic Ammonium Gemini Surfactant with Anionic Glutamic Acid Surfactant in Aqueous Solution.

The aggregation behaviors of the mixtures of cationic gemini surfactant 1,4-bis(dodecyl-N,N-dimethylammonium bromide)-2,3-butanediol (C12C4(OH)2C12Br2) and anionic amino acid surfactant N-dodecanoylglutamic acid (C12Glu) in aqueous solution of pH = 10.0 have been studied. The mixture forms spherical micelles, vesicles, and wormlike micelles at 25 °C by changing mixing ratios and/or total surfactant concentration. Then these aggregates undergo a series of transitions upon increasing the temperature. Smaller spherical micelles transfer into larger vesicles, vesicles transfer into solid spherical aggregates and then into larger irregular aggregates, and entangled wormlike micelles transfer into branched wormlike micelles. Moreover, the larger irregular aggregates and branched micelles finally lead to precipitation and clouding phenomenon, respectively. All these transitions are thermally reversible, and the transition temperatures can be tuned by varying the mixing ratios and/or total concentration. These temperature-dependent aggregate transitions can be elucidated on the basis of the temperature-induced variations in the dehydration, electrostatic interaction, and hydrogen bonds of the headgroup area and in the hydrophobic interaction between the hydrocarbon chains. The results suggest that the surfactants carrying multiple binding sites will greatly improve the regulation ability and temperature sensitivity.

Shape-controlled CH3NH3PbI3 nanoparticles for planar heterojunction perovskite solar cells

Hybrid organic/inorganic perovskites such as methylammonium lead iodide (CH3NH3PbI3) are potential candidates for thin-film photovoltaics because of their excellent cost- and energy-efficient light absorption. In this work, we have prepared CH3NH3PbI3 nanoparticles (NPs) on the TiOx/ITO glass substrates by a simple spin-coating method to control the size and shape of NPs. The effect of varying the weight percentage (wt %) of ionic liquid (IL) has also been investigated. Analysis of the films revealed spherical NP morphology in the presence of 1, 3, and 7 wt % IL with respective diameters of 540, 350, and 600 nm. Conversely, 10 wt % IL resulted in irregular aggregation of NP blocks. The power conversion efficiency (PCE) changed upon varying the NP size, shape, and morphology. The optimization of the concentration with 3 wt % IL yielded NPs with the most uniform shape, size, and morphology and, consequently, the maximum PCE.

Insights into the Role of Biomineralizing Peptide Surfactants on Making Nanoemulsion-Templated Silica Nanocapsules.

We recently developed a novel approach for making oil-core silica-shell nanocapsules using designed bifunctional peptides (also called biomineralizing peptide surfactants) having both surface activity and biomineralization activity. Using the bifunctional peptides, oil-in-water nanoemulsion templates can be readily prepared, followed by the silicification directed exclusively onto the oil droplet surfaces and thus the formation of the silica shell. To explore their roles in the synthesis of silica nanocapsules, two bifunctional peptides, AM1 and SurSi, were systematically studied and compared. Peptide AM1, which was designed as a stimuli-responsive surfactant, demonstrated quick adsorption kinetics with a rapid decrease in the oil-water interfacial tension, thus resulting in the formation of nanoemulsions with a droplet size as small as 38 nm. Additionally, the nanoemulsions showed good stability over 4 weeks because of the formation of a histidine-Zn(2+) interfacial network. In comparison, the SurSi peptide that was designed by modularizing an AM1-like surface-active module with a highly cationic biosilicification-active module was unable to effectively reduce the oil-water interfacial tension because of its high molecular charge at neutral pH. The slow adsorption resulted in the formation of less stable nanoemulsions with a larger size (60 nm) than that of AM1. Besides, both AM1 and SurSi were found to be able to induce biomimetic silica formation. SurSi produced well-dispersed and uniform silica nanospheres in the bulk solution, whereas AM1 generated only irregular silica aggregates. Consequently, well-defined silica nanocapsules were synthesized using SurSi nanoemulsion templates, whereas silica aggregates instead of nanocapsules predominated when templating AM1 nanoemulsions. This finding indicated that the capability of peptide surfactants to form isolated silica nanospheres might play a role in the successful fabrication of silica nanocapsules. This fundamental study provides insights into the design of bifunctional peptides for making silica nanocapsules.

Establishment of primmorphs from three Red Sea sponge species

Background Primmorphs are a special form of 3D-cell aggregates obtained from sponge cells. They can be used as biofermenters for the production of bioactive secondary metabolites. In the commercial development of sponge-derived drug leads, the production of primmorphs is one of the methods proposed to solve the supply problem. In addition, using primmorphs for the production of drugs can preserve the sponge population from extinction by producing enough quantities of the extracts and compounds that present in wild sponges. Objectives The presented work aimed to produce primmorphs of Red Sea sponges Hemimycale aff arabica , Stylissa carteri , and Crella (Yvesia) spinulata as long-term cultivation in vitro and identify the impact of different cell densities on their formation and growth. Results Microscopic studies suggested that primmorphs are formed through four stages: amorphous large cell floc within 1–3 h; small irregular cell aggregations in 1 day; large primary cell aggregations and round-shaped primmorphs after 3 days. Primmorphs of C. spinulata and S. carteri remained alive for 3–6 months. The primmorphs of H. arabica remained alive for 1 month. Long-term primmorph cultivation in vitro allows the creation of a controlled live model under experimental conditions. Conclusion This work may provide a solution to the ‘supply problem’ in the commercial development of sponge-derived drugs, as primmorphs can be used as biofermenters for bioactive secondary metabolite production. In addition, primmorphs can be used to study the morphogenesis of their sponges at different stages and transdifferentiation as well as the processes of spiculogenesis.

Shear induced self-thickening of chitosan/β-cyclodextrin compound solution

The molecular association and rheological behavior of the compound solutions of chitosan (CS) and β-cyclodextrin (CD) were investigated. The results show that an appropriate amount of CD could significantly affect the viscoelastic behavior of CS aqueous solution. The CS/CD compound solution presents an obvious multiple shear-thinning and a subsequent shear induced thickening (SIT) behavior which is similar to that of chitosan-grafted polyacrylamide aqueous solution, depending on the mass ratio of CD and CS. Too high or too low CD concentration is unfavorable for shear induced self-thickening of the CS/CD compound solution when CS concentration is fixed. TEM observations of the CS/CD compound solution show that larger CS–CD aggregates induced by hydrogen bonding appear with CD concentration increasing, and result in the increases of viscosity and moduli, which are in agreement with the results of steady and oscillation flows. The increased viscosity of the CS/CD compound solution after strong shearing is attributed mainly to the larger and irregular hydrogen-bonded aggregates inclined to connect into large pieces instead of isolated spheres. This superior and unique rheological property of the compound solution can be promisingly applied for various industrial fields in which accurate control of the solution rheology is required.

Structure and Properties of ZrO2–MgO Powders

It have been studied magnesia stabilized zirconia (ZrO2-MgO) powders produced by high-frequency decomposition of water salt solutions. It have been shown that due to precursor dissociation powders consist of spherical particles with smooth surface and irregular hollow aggregates resembling foam. An increase in the magnesium concentration in the precursor has an effect on the powder properties, namely, the specific surface decreases significantly and the bulk density increases. Zirconia in the nanostructured state is present only in the powders with 8.6 and 13.9 mole% MgO, with the size of the c-ZrO2 crystallites in them no more than 100 nm. In powder with 43.3 mole% of MgO the magnesia content in c-ZrO2 solid solution corresponds to its solubility limit of 22.2 mole% at temperature 2100°C.

Flocculated Laponite–PEG/PEO dispersions with monovalent salt, a SAXS and simulation study

It is well-known that clay can form lamellar structures i.e. tactoids, and recently it has been shown that the tactoid formation is dependent on the platelet diameter. To the authors knowledge, no tactoid formation has been observed for montmorillonite platelets with a diameter less than 60nm. In this study, small angle X-ray scattering in combination with coarse-grained modeling and molecular dynamics simulations have been utilized to study the sediment of Laponite–polyethylene glycol/polyethylene oxide (PEG/PEO) at elevated salt concentrations (150mM–1M). Laponite consists of platelets with a diameter of 25nm and it is known to have a relatively monodisperse size-distribution. At pH 10, the face of the platelets has a strong negative charge, whereas the rim is slightly positive. Here we show that it is possible to induce tactoids for Laponite if two constraints are fulfilled: (1) addition of high amount of salt such as NaCl, and (2) addition of a neutral polymer such as PEG. The role of the salt is to screen the repulsive interactions between the platelets and the role of the polymer is to bridge the platelets together: hence the loss in configurational entropy of the polymer is counteracted by the gain in attractive polymer–platelet interaction. As the concentration of NaCl and/or PEG increases, the Bragg peak becomes sharper, which is an indication of that larger tactoids are formed.Comparison between Laponite and montmorillonite shows that the interlayer distance between the platelets increases linearly with an increased Debye screening length for both type of clays, whereas the structure peaks of Laponite are broader compared to the montmorillonite. We argue that the main reason to the latter is due to the size of the platelets: (i) smaller platelets are less rotationally restricted and (ii) the effect of positive edge charges is larger when the platelets are smaller, which results in more irregular aggregates. In absence of the polymer, montmorillonite form tactoids above ∼0.3MNaCl whereas Laponite does not.Even though the model used is simple, we find qualitative agreement between experiments and simulations, which verifies that the underlying physics for tactoid formation is captured.

Microwave assisted reflux synthesis of NiCo2O4/NiO composite: Fabrication of high performance asymmetric supercapacitor with Fe2O3

NiCo2O4/NiO nanocomposite is successfully synthesized by rapid microwave assisted reflux method at various reaction times. XRD analysis is performed to reveal the crystalline nature and the compound formation. Further, the chemical environment of the surface composition of NiCo2O4/NiO is identified by X-ray Photoelectron spectroscopy. The morphological analysis (FESEM and TEM) of the composite showed that the formation of bundle like irregular large aggregates, which consists of nearly spherical particles. The maximum specific capacitance of 1924Fg−1 at 1mVs−1 in 1M KOH electrolyte with an excellent energy density of 75WhKg−1 at a power density of 103Wkg−1 is revealed for the NiCo2O4/NiO electrode. An asymmetric supercapacitor (ASC) is constructed using optimized NiCo2O4/NiO as positive and synthesized Fe2O3 as negative electrodes. This novel NiCo2O4/NiOǁFe2O3 architecture provides superior capacitive performance with a specific capacitance of 417Fg−1 at 1mVs−1. Subsequently the charge-discharge analysis exhibits the specific capacitance of 79Fg−1 at 1mAcm−2. The fabricated asymmetric supercapacitor (ASC) delivers an energy density of 19Whkg−1 at 157Wkg−1. Moreover, it provides an excellent cycle stability of about 97% capacitance retention over 5000 cycles.

Controlled Growth of Ferrihydrite Branched Nanosheet Arrays and Their Transformation to Hematite Nanosheet Arrays for Photoelectrochemical Water Splitting.

The morphology engineering represents an alternative route toward efficient hematite photoanodes for photoelectrochemical (PEC) water splitting without changing the chemical composition. In this work, a facile and mild solvothermal synthesis of unique ferrihydrite branched nanosheet arrays vertically aligned on FTO substrate was achieved at around 100 °C. The hierarchical branched ferrihydrite nanosheet arrays consisted of tiny branches up to 40 nm in length grown almost vertically on stem nanosheets ∼10 nm in thickness. Moreover, the variation of the morphology of the ferrihydrite nanostructures from bare nanosheet arrays through branched nanosheet arrays to dense branched structures can be readily achieved through the regulation of the reaction time and temperature. The obtained ferrihydrite branched nanosheet arrays can be in situ transformed into α-Fe2O3 nanosheet arrays with small surface protrusions upon annealing at 550 °C. After a simple postgrowth Ti-doping process, the resulting Ti-doped α-Fe2O3 nanosheet arrays showed a good PEC performance for water splitting with a photocurrent density of 1.79 mA/cm(2) at 1.6 V vs RHE under AM 1.5G illumination (100 mW/cm(2)). In contrast, the Ti-doped irregular aggregates of the α-Fe2O3 nanograins transformed from dense ferrihydrite branched structures exhibited a much lower photocurrent density (0.41 mA/cm(2) at 1.6 V vs RHE), demonstrating the important influence of the morphology of α-Fe2O3 photoanodes on the PEC performance.

Aggregate particles in the plumes of Enceladus

Estimates of the total particulate mass of the plumes of Enceladus are important to constrain theories of particle formation and transport at the surface and interior of the satellite. We revisit the calculations of Ingersoll and Ewald (Ingersoll, A.P., Ewald, S.P. [2011]. Icarus 216(2), 492–506), who estimated the particulate mass of the Enceladus plumes from strongly forward scattered light in Cassini ISS images. We model the plume as a combination of spherical particles and irregular aggregates resulting from the coagulation of spherical monomers, the latter of which allows for plumes of lower particulate mass. Though a continuum of solutions are permitted by the model, the best fits to the ISS data consist either of low mass plumes composed entirely of small aggregates or high mass plumes composed of mostly spheres. The high particulate mass plumes have total particulate masses of (166±42)×103kg, consistent with the results of Ingersoll and Ewald (Ingersoll, A.P., Ewald, S.P. [2011]. Icarus 216(2), 492–506). The low particulate mass plumes have masses of (25±4)×103kg, leading to a solid to vapor mass ratio of 0.07±0.01 for the plume. If indeed the plumes are made of such aggregates, then a vapor-based origin for the plume particles cannot be ruled out. Finally, we show that the residence time of the monomers inside the plume vents is sufficiently long for Brownian coagulation to form the aggregates before they are ejected to space.

Characteristics of PM10 and PM2.5 at Mount Wutai Buddhism Scenic Spot, Shanxi, China

A survey was conducted to effectively investigate the characteristics of airborne particulate pollutants PM10 and PM2.5 during the peak tourist season at Mount Wutai Buddhism scenic spot, Shanxi, China. Characteristics of the PM10 and PM2.5 in Wu Ye Temple (core incense burners), Manjusri Temple (a traffic hub), Yang Bai Lin Village (a residential district), and Nan Shan Temple (located in a primitive forest district), were determined. The results showed that the PM10 concentration was more than 1.01–1.14 times higher than the threshold (50 μg/m3) of World Health Organization Air Quality Guidelines (2005), and the PM2.5 concentration was 1.75–2.70 times higher than the above standard (25 μg/m3). Particle size analysis indicated that the distribution of fine particulate matter in Wu Ye Temple ranged from 0 to 3.30 μm. In other sampling points, the fine particulate was mainly distributed in the range of 0–5.90 μm. The particulates in Wu Ye Temple were mainly characterized by spherical, rod-like, and irregular soot aggregates (PM10) and spherical particles of dust (PM2.5). Manjusri Temple and Yang Bai Lin Village predominantly exhibited irregular soil mineral particulate matter (PM10), and amorphous ultrafine soot particulate matter (PM2.5).

Experimental evidence of how the fractal structure controls the hydrodynamic resistance on granular aggregates moving through water

Summary A comprehensive set of experiments was carried out to investigate the effect of the fractal architecture of granular aggregates on the free-fall acceleration through a still water column. Test aggregates were first generated numerically with a method that allowed to control the fractal dimension d and, next, three stochastic replicates were lithographically fabricated for each of six values of d ranging between 1.9 and 2.7. The recorded position, velocity and acceleration served to analyze their dynamics in the Reynolds and Galilei number space, and to calculate the momentum rate of change and the intensity of drag (viscous and impact) and inertial forces (added mass and Basset–Bousinnesq). Analysis of these forces highlighted a strong dependence on d ; additionally, integration of these forces in the particle momentum equation allowed to identify an additional resistance R x that showed a strong correlation with d . A correlation analysis of R x with various scaling laws combining velocity and acceleration suggested that R x could be described by a nonlinear drag force and a force intermediate between drag and inertia. It was therefore concluded that irregular granular fractal aggregates accelerating in water are subject to highly complex and nonlinear hydrodynamic effects caused by surface roughness and volume porosity, and that these effects have tight connection with the internal and external fractal characteristics of the aggregates.

An Example of Synorogenic Sediment-Hosted Copper Mineralization: Geologic and Geochronologic Evidence from the Paleoproterozoic Nussir Deposit, Finnmark, Arctic Norway

Sediment-hosted copper-silver mineralization in the Raipas Supergroup of the Repparfjord tectonic window of Finnmark, northernmost Norway, is present in two main stratigraphic horizons at Nussir and Ulveryggen. The stratigraphically lower Ulveryggen deposit is hosted by irregular lenses of dominantly fluviatile sandstone and conglomerate, whereas the Nussir deposit, with a strike length of ~9 km, is associated with dolomitic siltstone and dolomite. Both deposits display intense structural control, and apart from the classic stratiform geometry of the disseminated cupriferous sulfides, high-grade mineralization includes abundant foliation parallel and transgressive veinlets, fissures, and irregular lenses and aggregates, with or without quartz, carbonate, chlorite, and biotite gangue. A close association with ductile deformation is apparent. Although scarce, molybdenite occurs intimately associated with the cupriferous sulfides at Nussir, in a paragenetic sequence comprising chalcopyrite-bornite-molybdenite-chalcocite-neodigenite in both the stratiform disseminated and veinlet mineralization. U-Pb zircon dating of a tuffaceous horizon from the dominantly volcanic Nussir Group, collected 60 m above the ore horizon at Nussir, yielded an age of 2073.1 +23.2/−12.4 Ma that confirms accumulation in an intercontinental rift or island-arc environment during construction of the Paleoproterozoic Columbia supercontinent. Re-Os geochronology on Nussir molybdenite returned ages of 1761 ± 8 and 1768 ± 7 Ma, which represent the timing of the copper-silver mineralization in the area. This age, the oldest direct, unambiguous determination reported for a sediment-hosted copper deposit, implies that the copper mineralization took place ~300 m.y. after the sedimentation and volcanism responsible for the host sequence, and syntectonically with the Svecofennian (Svecokarelian) orogeny in the Fennoscandian Shield.

Grumiplucite from the Rudňany deposit, Slovakia: a second world-occurrence and new data

Grumiplucite, ideally HgBi2S4 was identified at the Droždiak vein, Rudňany deposit (Spissko-gemerske Rudohorie Mts., Slovakia). This rare Hg-sulfosalt forms metallic lead-grey to steel-grey, prismatic to acicular crystals up to 1 cm long, often grouped into irregular aggregates. It occurs in cavities of siderite with abundant cinnabar, Hg-rich tetrahedrite and chalcopyrite aggregates. Minor quartz or barite crystals and microscopic aggregates of Sb-rich bismuthinite to Birich antimonite were also observed. On the basis of chemical analyses, two types of grumiplucite were distinguished at the Rudňany deposit. The first is close to an ideal composition and has empirical formula Hg0.99Bi1.94S4.08 (based on 7 apfu). The second is characterized by regularly elevated contents of Sb ranging from 0.02 to 0.77 apfu. Grumiplucite is monoclinic, space group C2/m, with unit-cell parameters refined from X-ray powder data: a = 14.172(2), b = 4.0525(7), c = 13.975(1) A, β = 118.257(8)o and V = 707.0(2) A3 (Sb-free) and a = 14.183(1), b = 4.0538(5), c = 13.980(1) A, β = 118.239(1)o and V = 708.1(2) A3 (Sb-rich). Raman spectra for grumiplucite crystals with variable Sb contents are mutually well comparable. Therefore it seems that different Sb occupation does not affect the energy and intensity of Raman bands and they significantly differ from spectra of particularly structure-related mineral livingstonite, HgSb4S8. The dominant feature in the Raman spectra of grumiplucite is a series of spectral bands that corresponds to the stretching and bending vibrations of BiS5 polyhedra and Hg–S bonds.

Phosphate minerals from the hydrothermal quartz veins in specialized S-type granites, Gemerská Poloma (Western Carpathians, Slovakia)

An interesting association of phosphate minerals (fluorapatite, triplite, arrojadite-group minerals and viitaniemiite) was studied from intra-granitic hydrothermal quartz veins with minor amounts of albite, orthoclase, muscovite, fluorite, rhodochrosite, arsenopyrite, pyrite, bismuthinite and kobellite. The veins occur in highly evolved, Permian topaz-zinnwaldite leucogranite at the Elisabeth adit near Gemerska Poloma, Gemeric Unit, Western Carpathians (eastern Slovakia). Fluorapatite is enriched in Mn (similar to 4 wt. % MnO, 0.3 apfu Mn) and frequently replaced by triplite, representing the first known triplite occurrence in Western Carpathians. This mineral forms irregular aggregates (<= 7 cm across), Mn/(Mn + Fe) atomic ratio of which attains 0.68 to 0.78 and F/(F + OH) = 0.89-0.92. Fluorarrojadite-(BaNa) to its Mn-dominant analogue fluordickinsonite-(BaNa) (both minerals still not approved by IMA-CNMNC) occurs as aggregates up to 2 cm across, showing Sr-rich (similar to 1.7 wt. % SrO, similar to 0.36 apfu Sr) and Sr-poor (<= 0.6 wt. % SrO, <= 0.13 apfu Sr) compositions with W site F/(F + OH) = 0.74-0.80 and M site Mn/(Mn + Fe) = 0.39-0.52. Rare viitaniemiite is Mn-rich (10 to 11 wt. % MnO, 0.34-0.38 apfu Mn). The phosphate mineralization in quartz represents a high-temperature hydrothermal assemblage. The F-rich Mn, Fe, Ca-bearing phosphates, fluorite, and muscovite precipitated most likely in presence of alkali-and fluorine-bearing post-magmatic fluids which altered primary magmatic minerals (especially Li-rich micas and alkali feldspars) and liberated some elements (Fe, Mn, Al, Ba, Sr, Na, K) from the adjacent granite.

Unusual morphological forms of hodrušite from the Rozália vein, Hodruša-Hámre near Banská Štiavnica (Slovak Republic)

Rare Cu–Bi sulphosalt, hodrusite, occurs in the Rozalia vein (levels X–XIV of the Rozalia mine, Hodrusa-Hamre ore deposit near Banska Stiavnica, central Slovakia) in two unusual morphological forms. The first type are brownish bronze thin acicular striated crystals, up to 3 mm long, in drusy cavities of quartz–hematite gangue, which are usually grouped into chaotic or irregular aggregates. The second hodrusite type comprises flattened columnar aggregates, up to 1.5 cm long, overgrown by hematite in quartz gangue. These aggregates are distinctly striated with brownish bronze colour and metallic lustre. Abundant W- and Al-rich hematite, chalcopyrite, kaolinite/dickite, siderite, baryte, rare bismuthinite and kupcikite were found in the association. The earliest columnar aggregates of hodrusite are locally substantially replaced by bismuthinite; these hodrusite–bismuthinite aggregates are further intensively pushed back by hematite displaying W- and Al-rich zones. Acicular crystals of hodrusite in gangue cavities were later than bismuthinite and hematite and their formation was related to remobilisation of Cu and Bi from earlier altered gangue. Powder X-ray diffraction data and chemical composition of both hodrusite types are similar; their unit-cell parameters were refined (monoclinic space group C2/m) as: a 17.552(5), b 3.905(1), c 27.167(9) A, β 92.44(3) o