W. Hofmeister

• Johannes Gutenberg University Mainz

Metamorphic gem corundum (mainly ruby) deposits are robust indicators of continent-continent collision processes. However, a systematic link of primary magmatic blue sapphire occurrences to orogenic belts is less understood. An example is the Ilmenogorsky alkaline complex, within the Ilmen Mountains region and part of the Uralian orogenic belt. The...

Natural aluminum oxide (α-Al2O3), the mineral corundum, is a component of some metamorphosed and igneous rocks and appears in secondary placers as detrital crystal fragments. Rare gem-quality corundum varieties-ruby and sapphire occur only in a few primary rock types (Giuliani et al., 2014; Hughes, 2017). This reflects the scarcity of geological en...

Corundum is a mineral frequently found in many magmatic and metamorphic rocks. Furthermore, its red variety ruby detected in orogenic belts is the rare but powerful indicators of plate collision events (Stern et al. 2013, Sorokina et al. 2017 etc.). Meanwhile, the genesis of sapphire and its accompanying minerals found in situ in primary beari...

K- feldspars in pegmatites from Luc Yen gem mining area, Yen Bai province, Vietnam were studied by XRF, XRD and Raman spectroscopy. Chemical analysis determined the K-Feldspars in the form of (K0.8909Na0.0388Ca0.002Pb0.0042Cs0.0024Rb0.0338)(Al0.9975Fe0.0053Ti0.0004)Si2.988O8. Both XRD and Raman spectroscopy indicated Luc Yen K-feldspars as orthocla...

In this paper, we study the influence of the Fe2O3 content on the Raman spectra of sapphires by confocal micro Raman spectroscopy and Electron Probe Micro Analysis (EPMA) on a wide variety of sapphire samples collected from 18 different mining regions. Almost all of the samples have a basaltic origin, which is often characterized by a high Fe2O3 co...

The subject of the paper is lead free bismuth layer structure oxides (1-x)Bi3TiNbO9-xBaBi2Nb2O9 (x=0; 1; 2; 3 mol). The influence of Bi3TiNbO9-xBaBi2Nb2O9 ratio on dielectric and structural properties was studied in a wide range of temperatures. Change in the ratio causes a decrease in the maximum value of dielectric permittivity and shifts the tem...

Luc Yen is a well-known gem mining area for ruby, sapphire, spinel, tourmaline and green K-feldspar, located in Yen Bai province in the north of Vietnam, 270 km northwest from the capital city Hanoi. Green K-feldspars can be found together with tourmalines in pegmatite bodies, and they have been of scientific interests as many of them possess disti...

Discovered during the late 1970s, the Snezhnoe ruby and sapphire deposit in Tajikistan was active until the collapse of the former Soviet Union in the early 1990s and the outbreak of regional conflicts. This marble-hosted occurrence has seen renewed interest, as it is a large and potentially productive deposit that has not been sufficiently studied...

The single crystals of Gd7-xYxPd3 (x = 0-6) system were grown by the Czochralski method. All samples crystallized in Th7Fe3-type of crystal structure. The Gd ions in this crystal structure are located in the triangular configurations in three nonequivalent crystallographic positions. The XRD and XPS examinations allow to determine which positions o...

Concordant ultramafic rocks are exposed in the lower crustal granulites of Sri Lanka. The ultramafic rocks at Rupaha had emplaced early. They had been subjected to deformation and granulite facies metamorphism at 850oC at 9 kbar during the Pan-African tectono-thermal episode. The results of thermometry of ultramafic rocks are consistent with those...

Single crystal inclusions in natural single crystals bear a lot of information on the genesis and phase stabilities between host and guest crystals. Not only parameters of the natural environment of crystallization may be elucidated, also the history of up-rise within the earth to the surface and the development during procedures, eventually applie...

A comparative analysis on the physical nature of the fly ashes, obtained from three thermal power plants, situated in West Bengal, India is presented in this work. The particle size of the fly ash samples are estimated, and their morphology and compositional analysis are made. These samples are crystalline, and the major components are mullite and...

Physical Characteristics of Fly Ashes from Three Thermal Power Plants in West Bengal, India: A Comparative Study

Corundum from Snezhnoye deposit in Tajikistan was investigated using the complex of mineralogical methods. Special features of corundum ontogeny were studied in details with identifying its generations. The role of ontogeny in formation of the gem quality ruby was determined.

Raman spectroscopy is a powerful tool in identifying different calcium carbonate polymorphs. Here, the method is applied to cultured pearls from freshwater (genus Hyriopsis) and marine bivalve species (Pinctada maxima) as well as to shells of Diplodon chilensis patagonicus bivalves. Raman spectra for vaterite, detected for the first time in an adul...

This paper presents the characteristics of iron oxides obtained through thermal degradation of a molecular ferrimagnet, {N(n-C4H9)4[FeIIFeIII(C2O4)3]}∞ and sheds light on the reaction pathways of degradation. The powder XRD pattern and the IR spectra of the degraded material reveal the formation of hematite. The SEM study exhibits that the degraded...

Metamict minerals contain radioactive elements that degrade their crystal structure. Unlike other metamict minerals, annealing process under ambient pressure do not lead to direct recrystallization of steenstrupine.

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Gd4Y3Pd3 belongs to Gd7−xYxPd3 series examined as prospective materials for magnetic refrigeration. Single crystal of Gd4Y3Pd3 was grown by the Czochralski method from a levitated melt. Investigations of X-ray diffraction, electronic structure, dc-magnetization M(T), ac-magnetic susceptibility (ac-χ) and electrical resistivity (ρ) for the hexagonal...

The growth of gem quality metamorphic minerals is most likely in fluid rich systems, where growth rate exceed the rate of nucleation. This condition typically occurs when crystallizing is close to equilibrium. This communication discusses metasomatic growth of corundum crystals at the boundary between ultramafic and acidic granulites. The phase pet...

Electronic structure, temperature dependences of the lattice parameters and magnetic properties of a crystal belonging to the series Gd7−xYxPd3 has been measured. Gd3Y4Pd3 orders ferromagnetically at 197K and all measured physical properties show a strong anisotropy. The saturation magnetic moment per Gd ion is enhanced in relation to the theoretic...

Experimental results of the single-crystal X-ray diffraction, XPS, ac-magnetic susceptibility (ac-χ), dc-magnetization M(T), and electrical resistivity (ρ) measurements for the hexagonal Th7Fe3-type Gd5Y2Pd3 single crystal are presented. Anomalies in (ac-χ), (T) and M(T)-curves have allowed to establish that Gd5Y2Pd3 undergoes a long-range ferromag...

Raman spectroscopy was used to study vaterite samples of biological, geological and synthetic origin. The Raman band positions and the full width at half-maximum (FWHM) of the lattice modes and the internal modes of the carbonate ion of all specimens show no significant differences between vaterites of different origin. With increasing Mg concentra...

The pair aragonite and calcite are some of the most intensively studied polymorphous minerals. These CaCO3 polymorphs are most commonly observed in biological minerals produced by marine molluscs, whereas in freshwater molluscs mostly aragonite and vaterite, the third CaCO3 polymorph is identified (e.g. Wehrmeister et al., 2007). Vaterite is the th...

Shells and pearls of unionid mussels (Hyriopsis cumingii, Margaritifera margaritifera, Diplodon chilensis patagonicus) were studied by high resolution microbeam methods and -computer tomography to gather insight into the nanostructure and chemical composition of nacre and prism layers. Natural and cultured pearls are formed by many mollusc species...

Freshwater and marine cultured pearls form via identical processes to the shells of bivalves and can therefore serve as models for the biomineralization of bivalve shells in general. Their nanostructure consists of membrane-coated granules (vesicles) which contain amorphous calcium carbonate (ACC) at the beginning of the biomineralization sequence,...

Vaterite and aragonite polymorphs in freshwater cultured pearls from mussels of the genus Hyriopsis (Unionidae) were structurally and compositionally characterized by Raman spectroscopy, Micro computer tomography, high resolution field emission scanning electron microscopy, electron microprobe analysis and laser ablation inductively coupled plasma...

The metastable calcium carbonate polymorph vaterite has recently been found to occur commonly in freshwater cultured pearls from Japan and China. Organic pigment molecules in these vaterite regions of freshwater cultured pearls were analysed by resonance and near-resonance micro-Raman spectroscopy, in single spectra and in mapping modes and are com...

The lattice parameters, the electrical resistivity and magnetic susceptibility of the Gd7Rh3 and Gd7Pd3 single crystals have been measured and the electronic structure of both the compounds has been obtained from a careful analysis of XPS spectra. These two compounds crystallize in the hexagonal Th7Fe3 type of structure with the same ratio c/a = 0....

The lattice parameters, the electrical resistivity and magnetic susceptibility of the Gd7Rh3 and Gd7Pd3 single crystals have been measured and the electronic structure of both the compounds has been obtained from a careful analysis of XPS spectra. These two compounds crystallize in the hexagonal Th7Fe3 type of structure with the same ratio c/a=0.63...

Japanese and Chinese beaded-and non-beaded-nucleated cultured freshwater pearls of good quality were investigated with Raman spectroscopy and LA-ICP-MS. In 50% of the investigated non-beaded samples vaterite was identified by Raman spectrometry in polished cross-sections near the centre of the pearl as well as in small blemishes on the pearl surfac...

Thermal variation of the lattice parameters, magnetic susceptibility and magnetization of a Dy 5 Pd 2 single crystal has been measured. The single crystal obtained by the Czochralski method crystallized in the cubic Dy 5 Pd 2 type structure. The compound exhibits two characteristic temperatures. The former equals about 40 K, and the latter about 20...

Generally, it has been assumed that signal intensity variations in back-scattered electron (BSE) images of minerals are mainly controlled by chemical heterogeneity. This is especially true for images of single crystals, where effects of different crystal orientations with respect to the incident beam on the observed BSE are excluded. In contrast, w...

Ternary GdPdX (X = Al, Si, Ga, Ge, In, Sn) compounds, obtained by the induction melting, crystallize in the stable orthorhombic structure similarly to GdRhAl. The magnetic ordering temperatures of the GdPdX and GdRhAl compounds are close to 30 K. The electrical resistivity measurements of the GdPdX compounds revealed that at higher temperatures mai...

The concepts of template-induced crystallization on self-assembled monolayers (SAMs) and the use of polymer additives are combined into a new strategy, where, through the cooperative interaction of a SAM matrix involved in the nucleation process, poly(acrylic acid), a dissolved polyelectrolyte, and the dissolved ions, hierarchically ordered mineral...

The Raman mapping technique provides a non-destructive means of studying internal growth textures and other micro-structural heterogeneity inside diamond single-crystals. Raman maps showing distribution patterns of the bandwidth (FWHM) of the main first-order lattice vibration of diamond (LO = TO phonon at similar to 1332 cm(-1)) along two-dimensio...

The effects of palladium (Pd) catalyst film thickness and ammonia (NH3) in thermal chemical vapor deposition (CVD) growth of carbon nanotubes (CNTs) are systematically compared per the resulting morphologies, Raman spectra and field emission characteristics. The CNT field emitters were tested under identical experimental configurations. Field emiss...

We have studied high-pressure inclusions (Ca-silicates, coesite, graphite) in three large diamonds, one from the Kankan district, Guinea, and the other two from the Panda kimberlite, Ekati diamond mines, Canada. Using the in situ point-by-point mapping technique with a confocal Raman system, the mineralogy of the inclusions, as well as their area d...

We report on the first study of the cleaved (001) topaz surface and the characterization of the chemical composition and atomic arrangement of the surface. We conclude that there is strong evidence for a hydroxyl group termination appropriate for further chemical reactions. The surface itself is easily accessible, atomically flat and suitable for p...

¶Diffusion modeling of zoning profiles in garnet rims from mafic granulites is used to estimate cooling rates in the Proterozoic basement of Sri Lanka, which represents a small, but important fragment of the Gondwana super-continent. Metamorphic peak temperatures and pressures, estimated with two-pyroxene thermometry and garnet–clinopyroxene–plagio...

The Ratnapura and Elahera gem fields of Sri Lanka have been renowned for their high quality gemstone for centuries. An improved understanding of the origin of gem minerals does not only have important regional geologic implications, but is also of economic significance. This paper presents the origin of some important gem minerals at Bakamuna (a kn...

Organic and other volatile metal(loid) species (e.g. hydrides) in environmental gases can be determined with high sensitivity and selectivity by low-temperature gas chromatography coupled on-line to plasma mass spectrometry (LTGC/ICP–MS). A standard reference solution is analysed simultaneously for calibration of the results as well as for monitori...

Magmatic activities in the Saar-Nahe-Trough began in the upper Carboniferous. It resulted in the formation of: 1) dark-coloured basic to intermediate intrusions of high level sills or dykes, 2) thick volcanic flows of basic to intermediate chemistry, 3) extensive laccoliths (subvolcanoes) of light-coloured rhyolites, and 4) diatremes with basic, ma...

Brucite-related double layer structures are characterized by a regular but distinct stacking of [MexMe (OH)2x+2]+ octahedral layers with ordered cation distribution and usually x = 2 or x = 3, alternating with anionic {A·nH2O}- interlayers. The stacking sequence of the layers is rhombohedral (3R) or hexagonal (2H) parallel to [001]. Evidence of ord...

CuFe 2 (PO 4 ) 2 (OH) 2 cristallise dans le systeme monoclinique avec le groupe d'espace P2 1 /n. Affinement de la structure jusqu'a 0,037. Des octaedres Fe(OH) 2 O 4 et des polyedres deformes Cu(OH) 2 O 4 ont des faces communes et forment des groupes octaedriques triples CuFe 2 (OH) 4 O 8

Wie Röntgen- Einkristalluntersuchungen zeigen, kristallisiert die Titelverbindung in der Raumgruppe Pl mit Z=4.

X-ray single crystal work on arsenbrackebuschite, Pb2(Fe, Zn) (OH, OH2) (AsO4)2 (with Fe∶Zn∼2∶1), gave space groupP21/m witha 0=7.763(1),b 0=6.046(1),c 0=9.022(1) Å, β=112.5(1)°,V=391.2(1) Å3,Z=2 and ρx =6,54 g/cm3. 3-dimensional Fourier syntheses and least-squares refinement (finalR=0.073) showed that the new mineral belongs to a group of lead min...