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Quartz (trigonal, low-temperature α-quartz) is the most important polymorph of the silica (SiO2) group and one of the purest minerals in the Earth crust. The mineralogy and mineral chemistry of quartz are determined mainly by its defect structure. Certain point defects, dislocations and micro-inclusions can be incorporated into quartz during crystallisation under various thermodynamic conditions and by secondary processes such as alteration, irradiation, diagenesis or metamorphism. The resulting real structure is a fingerprint of the specific physicochemical environment of quartz formation and also determines the quality and applications of SiO2raw materials. Point defects in quartz can be related to imperfections associated with silicon or oxygen vacancies (intrinsic defects), to different types of displaced atoms, and/or to the incorporation of foreign ions in lattice sites and interstitial positions (extrinsic defects). Due to mismatch in charges and ionic radii only a limited number of ions can substitute for Si4+in the crystal lattice or can be incorporated in interstitial positions. Therefore, most impurity elements in quartz are present at concentrations below 1 ppm. The structural incorporation in a regular Si4+lattice site has been proven for Al3+, Ga3+, Fe3+, B3+, Ge4+, Ti4+, P5+and H+, of which Al3+is by far the most common and typically the most abundant. Unambiguous detection and characterisation of defect structures in quartz are a technical challenge and can only be successfully realised by a combination of advanced analytical methods such as electron paramagnetic resonance (EPR) spectroscopy, cathodoluminescence (CL) microscopy and spectroscopy as well as spatially resolved trace-element analysis such as laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and secondary-ion mass spectrometry (SIMS). The present paper presents a review of the state-of-the-art knowledge concerning the mineralogy and mineral-chemistry of quartz and illustrates important geological implications of the properties of quartz.

Genetic models for the formation of uranium deposits almost invariably invoke the reduction of U(VI) to U(IV) as the deposition mechanism. However, the questions of when and how this reduction occurred are often not clear in most uranium deposits. For example, mineralization in the giant Olympic Dam Cu-U-Au-Ag deposit (Australia) occurs mainly in hematite-rich breccias of the oxidizing hematite-quartz-barite assemblage. Similarly, unconformity-related uranium deposits in the Athabasca Basin (Canada) are accompanied by extensive and intensive hematite- and quartz-rich alteration halos, pointing to a possible linkage between uranium mineralization and silicification. However, this linkage is not understood due to the lack of knowledge about the speciation and mechanism of uranium incorporation in microcrystalline and macrocrystalline silicas. In this contribution, microcrystalline silicas (agate and opal-CT) containing 27–137 ppm U have been investigated by microbeam synchrotron X-ray fluorescence mapping, microbeam synchrotron X-ray diffraction analysis, synchrotron X-ray absorption spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, and electron paramagnetic resonance spectroscopy. These data unravel the binding mechanism of uranyl silicate complexes in microcrystalline silicas and suggest a new mechanism of uranium deposition involving uranyl co-precipitation without the putative reduction process, providing a potential missing link between uranium mineralization and silicification for the formation of uranium deposits. In addition, new data on the uptake and long-term retention of elevated uranyl contents in microcrystalline silicas extend previous findings from their amorphous counterparts on these materials as an effective sink for uranium attenuation to higher temperatures, important to the storage and disposal of heat-generating nuclear waste in deep geological repositories.

To optimally design integrated energy systems a widely used approach is the Energy Hub. The conversion, storage and transfer of different energy vectors is represented by a coupling matrix. Yet, the coupling matrix restricts the configuration of the Energy Hub and the constraints, that can be included. This paper proposes a MILP based optimization framework, which allows a high variability and adaptability and is based on energy flows. The functionality of the developed framework is tested on four use cases depicting different system sizes and Energy Hub configurations. It is shown that the framework is able to simplify the design process of an Energy Hub.

Large single crystals of GdCa4O(BO3)3 (space group Cm) were grown by the Czochralski method. Dielectric, piezoelectric and elastic coefficients at room temperature as well as specific heat capacity, thermal expansion and cation disorder were studied employing a variety of methods including resonant ultrasound spectroscopy, differential scanning calorimetry, dilatometry and X-ray diffraction techniques. The electromechanical parameters (4 dielectric, 10 piezoelectric and 13 elastic stiffness coefficients) obtained on different samples are in excellent agreement indicating high internal consistency of our approach, whereas the values reported in literature differ significantly. The elastic behaviour of GdCa4O(BO3)3 resembles the one of structurally related fluorapatite, i.e. the elastic anisotropy is relatively small and the longitudinal effect of the deviations from Cauchy-relations exhibit a pronounced minimum along the direction of the dominating chains of cation polyhedra. GdCa4O(BO3)3 exhibits a maximum longitudinal piezoelectric effect of 7.67 × 10−12 CN−10, a value in the order of that of langasite-type materials. Significant changes of the calcium/gadolinium distribution on the 3 independent cation sites accompanied by characteristic anomalies of heat capacity and thermal expansion suggest processes of nonconvergent cation ordering above about 900 K in GdCa4O(BO3)3.

The chemical composition of different rocks as well as volatile-bearing and volatile-free minerals has been used to assess the presence of fluids in the Closepet batholith and to estimate the intensity of the fluid−rock interactions. The data were processed using polytopic vector analysis (PVA). Additional data include measurements of water content in the structure of volatile-free minerals and an examination of growth textures. The composition of mineral domains indicated formation/transformation processes with common fluid−mineral interactions. In general, the results suggested that the processes occurred in a ternary system. Two end-members were likely magmas and the third was enriched in fluids. In contrast, analysis of the apatite domains indicated that they likely formed/transformed in a more complex, four-component system. This system was fluid-rich and included hybrid magma with a large mafic component. PVA implies that the fluids do not appear to come from one source, given their close affinity and partial association with mantle-derived fluids. A dynamic tectonic setting promoting heat influx and redistribution, and interaction of fluids suggests that the formation/ transformation processes of minerals and rocks occurred in a hot-spot like environment.

Agates in Paleocene/Eocene tuffs from El Picado/Los Indios, Cuba were investigated to characterize the mineral composition of the agates and to provide data for the reconstruction of agate forming processes. The volcanic host rocks are strongly altered and fractured and contain numerous fissures and veins mineralized by quartz and chalcedony. These features indicate secondary alteration and silicification processes during tectonic activities that may have also resulted in the formation of massive agates. Local accumulation of manganese oxides/hydroxides, as well as uranium (uranyl), in the agates confirm their contemporaneous supply with SiO2 and the origin of the silica-bearing solutions from the alteration processes. The mineral composition of the agates is characterized by abnormal high bulk contents of opal-CT (&gt, 6 wt%) and moganite (&gt, 16 wt%) besides alpha-quartz. The presence of these elevated amounts of “immature” silica phases emphasize that agate formation runs through several structural states of SiO2 with amorphous silica as the first solid phase. A remarkable feature of the agates is a heterogeneous distribution of moganite within the silica matrix revealed by micro-Raman mapping. The intensity ratio of the main symmetric stretching-bending vibrations (A1 modes) of alpha-quartz at 465 cm−1 and moganite at 502 cm−1, respectively, was used to depict the abundance of moganite in the silica matrix. The zoned distribution of moganite and variations in the microtexture and porosity of the agates indicate a multi-phase deposition of SiO2 under varying physico-chemical conditions and a discontinuous silica supply.

Agate—a spectacular form of SiO2 and a famous gemstone—is commonly characterized as banded chalcedony. In detail, chalcedony layers in agates can be intergrown or intercalated with macro-crystalline quartz, quartzine, opal-A, opal-CT, cristobalite and/or moganite. In addition, agates often contain considerable amounts of mineral inclusions and water as both interstitial molecular H2O and silanol groups. Most agate occurrences worldwide are related to SiO2-rich (rhyolites, rhyodacites) and SiO2-poor (andesites, basalts) volcanic rocks, but can also be formed as hydrothermal vein varieties or as silica accumulation during diagenesis in sedimentary rocks. It is assumed that the supply of silica for agate formation is often associated with late- or post-volcanic alteration of the volcanic host rocks. Evidence can be found in association with typical secondary minerals such as clay minerals, zeolites or iron oxides/hydroxides, frequent pseudomorphs (e.g., after carbonates or sulfates) as well as the chemical composition of the agates. For instance, elements of the volcanic rock matrix (Al, Ca, Fe, Na, K) are enriched, but extraordinary high contents of Ge (>90 ppm), B (>40 ppm) and U (>20 ppm) have also been detected. Calculations based on fluid inclusion and oxygen isotope studies point to a range between 20 and 230 °C for agate formation temperatures. The accumulation and condensation of silicic acid result in the formation of silica sols and proposed amorphous silica as precursors for the development of the typical agate micro-structure. The process of crystallization often starts with spherulitic growth of chalcedony continuing into chalcedony fibers. High concentrations of lattice defects (oxygen and silicon vacancies, silanol groups) detected by cathodoluminescence (CL) and electron paramagnetic resonance (EPR) spectroscopy indicate a rapid crystallization via an amorphous silica precursor under non-equilibrium conditions. It is assumed that the formation of the typical agate microstructure is governed by processes of self-organization. The resulting differences in crystallite size, porosity, kind of silica phase and incorporated color pigments finally cause the characteristic agate banding and colors.

The morphology, chemical, and mineralogical composition of subsurface filamentous fabrics (SFF) from the Deccan Volcanic Province (DVP) were investigated to determine the origin of these spectacular aggregates. SFF occur in a wide variety of morphologies ranging from pseudo-stalactites to irregular fabrics and are classified as SFFIr (irregular) or SFFMa (matted). The SFF samples exhibit a thread-like (or filament-like) center from which mineral precipitation starts to form the final macroscopic morphologies. Detailed investigations revealed organic material (fungal chitin) in the innermost filamentous core, which may have acted as an initial nucleus for the mineralization processes. The morphometric characteristics of certain filamentous fabrics are very similar to those of microbial filaments and the fabrics formed from them but are clearly distinct from similar types of non-biological precipitates (fibrous minerals, speleothems, and &ldquo, chemical gardens&rdquo, ). These features indicate that the filamentous cores might be products of microbial communities that were active in the basaltic cavities. The SFF cross-sections display similar concentric layers of the mineral succession and reach thicknesses of several centimeters with spectacular lengths up to 100 cm and constant diameters. The typical mineralization sequence points to temporal variation in the chemical composition of the mineralizing fluids from Fe(Mg)-rich (Fe-oxides/-hydroxides, Fe-rich sheet silicates such as celadonite and di-/tri-smectite) to Ca-dominated (Ca-rich zeolites) and finally pure SiO2 (opal-CT, chalcedony, and macro-crystalline quartz). Assuming biological activity at least during the early mineralization processes, circumneutral pH conditions and maximum temperatures of 100&ndash, 120 &deg, C were supposed. The formation of filamentous cores including Fe-bearing phyllosilicates probably occurred near the surface after cooling of the lava, where the elements necessary for mineral formation (i.e., Si, Mg, Al, Fe) were released during alteration of the volcanic host rocks by percolating fluids.

Die Phasenlehre und das Verstandnis heterogener Gleichgewichte stellen ein sehr komplexes Gebiet dar. Hier sollen ausgehend von den Grundbegriffen das geometrische Verstandnis von unaren, binaren und im Ansatz ternaren Systemen erlautert werden. Dabei dienen viele Abbildungen dazu, in einzelnen Schritten das Verstandnis der Zusammenhange logisch aufzubereiten.

The study of the oldest surviving rock suites is crucial for understanding the processes that shaped the early Earth and formed an environment suitable for life. The metasedimentary and metavolcanic rocks of the early Archean Isua supracrustal belt contain abundant apatite, the geochemical signatures of which may help decipher ancient environmental conditions. However, previous research has shown that secondary processes, including amphibolite-facies metamorphism, have reset the original hydrogen isotope composition (δD) of apatite from the Isua belt; therefore, δD values are not indicative of primary conditions in the Archean. Here, we report the first in situ chlorine isotope (δ37Cl) analyses by Secondary Ion Mass Spectrometry (SIMS) from Isua apatite, which we combine with information from transmission electron microscopy, cathodoluminescence imaging, and spectroscopy, documenting the micron-scale internal features of apatite crystals. The determined δ37ClSMOC values (chlorine isotope ratios vs. standard mean ocean chloride) fall within a range from −0.8‱ to 1.6‱, with the most extreme values recorded by two banded iron formation samples. Our results show that δ37Cl values cannot uniquely document primary signatures of apatite crystals, but the results are nonetheless helpful for assessing the extent of secondary overprint.

Agates with spectacular micro-structural features were found in volcanic rocks at several occurrences in the Saar-Nahe region (Germany). These agates include spirals of several tens up to several hundreds of μm in size within zones lacking the characteristic structural agate banding. A combined mineralogical study by polarising microscopy, scanning electron microscopy, cathodoluminescence microscopy and spectroscopy, and electron backscatter diffraction provided evidence that the spirals consist of well-ordered trigonal α-quartz, whereas the surrounding matrix is composed of strongly disordered or amorphous SiO2phases. The quartz micro-crystals show a systematic rotation of the crystal orientation perpendicular to the direction of the spiral loops indicating helical growth.It is assumed that the spiral growth is initiated by dislocations with a screw component. The lacking symmetry of the strongly disordered or amorphous matrix initiated a curved development by a screw dislocation in a system far from equilibrium. The atoms/molecules are packed into spiral layers, which is energetically favoured in comparison with the incorporation into plane crystal faces. Such self-organisation growth and polymerisation initiated by a screw dislocation can produce variable spiral morphologies sometimes resembling living forms.

The Nomarski differential interference contrast (DIC) microscopy in the reflected–light visualizes a virtual surface relief of rock components through varying resistance to grinding and polishing of different mineral phases. In the case of sandstones, illustrated here with an example of the Cergowa sandstones (Lower Oligocene) from the Flysch Carpathians, the used analytical technique depicts a homogeneity with no or very weak relief in the surface morphology of all components besides clay particles, where a virtual relief is observed. Thereby, the Nomarski DIC imaging proved to be very useful in a distinction between an interstitial matrix and other binders of sedimentary rocks. Such separation with standard petrographic examinations is often far from clear which causes usually an overstatement of the matrix content and an incorrect rock classification. Such monotonous picture of sandstones as from the Nomarski DIC microscopy seems to be easy to apply in an image analysis. In the case of the Cergowa sandstones, an automatic extraction of clay matrix in an image analysis was disturbed by numerous replacements of some minerals (especially feldspars) by clay minerals that were detected as a matrix with an illusory relief. The applied manual approach in the ImageJ analysis programme pointed out: two of six analysed images were overestimated by means of the polarising microscopy. In both cases, the matrix content was estimated >15%, whilst in the Nomarski DIC images showed contents of 10.5% and 10.2%, what classifies them as arenites, not wackes. The presence of clay matrix in sandstones has a great influence on their petrophysical properties, including the most important porosity and permeability, a sufficient amount of which permits to accumulate crude oil or natural gas under adequate trapping conditions. Therefore, their correct extraction and measurement is so substantial.

A continental magmatic arc (the Famatinian magmatic arc) was developed on the western margin of Gondwana during the Early to Middle Ordovician. This has a northwestern orientation in the northern Chile-Argentina Andes between 21° and 26° south latitude with a northeastern directed subduction zone and developed on a continental crust represented by a metamorphic basement. A paleogeographical scheme for the Ordovician magmatic arc is proposed and two tectonic environments can be recognized from our own data and data from the literature: forearc and arc. The Cordon de Lila Complex can be assigned to a forearc position. Here the turbiditic flows become paralell to the northwestern elongation of the magmatic arc. The sedimentation in the frontal-arc high platform of the forearc is represented by stromatolitic limestones and a zone of phosphate production. The internal structure of the arc can be inferred from the petrographic composition of the turbidites: basaltic and andesitic lavas, dacitic and/or rhyolitic lavas and ash fall tuffs. Also the Quebrada Grande Formation was developed on the forearc. Plutonic Ordovician rocks testify the continuity of the magmatic arc. The data about the basement exposed in the present paper do not support the existence of the Arequipa-Antofalla Terrane.

Radiation-induced damage in quartz from the overlying Athabasca Supergroup sandstones and the basement host rocks at the Arrow uranium deposit in the southwestern margin of the Athabasca basin, Saskatchewan, has been investigated by electron paramagnetic resonance (EPR) spectroscopy as well as cathodoluminescence (CL) imaging and spectroscopy. Powder EPR spectra confirm that quartz from the Arrow deposit contains a suite of radiation-induced defects, including characteristic silicon vacancy hole centers formed from bombardment of α particles emitted from the radioactive decay of U, Th, and their daughter isotopes. The EPR intensity distribution of α particle-induced defects in detrital quartz close to the sandstone–basement unconformity suggests that uranium-bearing fluids at Arrow are restricted to areas directly above the basement-hosted mineralization. Pink quartz in the basement, which occurs as veins and breccias in spatial association with uranium mineralization, is characterized by elevated, homogeneously distributed radiation-induced defects, suggesting its crystallization from uranium-bearing fluids most likely linked to the main mineralization event. Smoky quartz in veins and cavities often exhibits characteristic α particle-induced CL rims, which crosscut the growth zoning and apparently record late uranium remobilization. Abundant radiation-induced defects in the basement at the Arrow deposit are restricted to quartz within ∼7 m from uranium mineralization, confirming structurally controlled fluid flows. These results highlight the application of radiation-induced defects in quartz for determining the loci of uranium-bearing fluids.

Energy systems with a high share of renewable energy sources (RES) require a large degree of flexibility due to the inherent volatility of wind and photovoltaic based power generation. Here, cross-sector coupling of the power and district heating system can add such flexibility and increase the self-consumption of RES. To couple these two systems, components such as electric boilers, heat storages and combined heat and power (CHP) systems must be optimally sized. Existing optimization algorithms mostly size the components based on volatile energy prices. In contrast, this paper investigates the sizing based on the reduction of network charges for different degrees of self-consumption in two future RES scenarios. For that, the operating mode of an existing CHP system is changed to "power-led" by introducing a hot water storage and an electrode boiler. The optimization determines the best design of the hot water storage and electrode boiler for a district of a town in Germany. It is shown, that such a system can add flexibility to a micro grid and increase the degree of self-consumption while reducing the network charges and thus being economical up to 60 % of self-consumption.

Multiple tools have been used to determine the sensitivity of phosphates from the early Archaean Barberton greenstone belt to transformation. The assessment of the degree of transformation is crucial for verifying data about the parameters of the paleo-environment. From the obtained results, three generations of phosphates can be distinguished. Group A is observed in cherts and banded iron formation BIF early-generation fluor-hydroxyapatite that precipitated from seawater. It is characterized by flat rare earth element (REE) patterns with a positive Eu anomaly and high Y/Ho ratio in the range of 54–70. Apatites in this group lack any visible indicators of secondary alterations at the micro- and nanoscales. Fourier transform infrared spectra indicate that these apatites are relatively rich in water, and, due to cationic substitution, their OH-stretching regions exhibit complex ordering and numerous component bands. The characteristics observed in the cherts and silicified felsic volcaniclastics of group B imply advanced metasomatic alteration. They exhibit light and heavy REE depletion and an absence of water in the halogen site. Nanoscale investigations reveal cracks, pores, nanofluid inclusions and nanochannellike structures, as well as inclusions. Group C is represented by igneous-derived apatites that partially reflect their igneous origin. The phosphates are predominantly fluorapatite with typical magmatic apatite REE distribution patterns. Imaging at the micro- and nanoscales indicates that they partially preserve the signature of igneous origin. It seems that some of the analyzed apatite partially preserved their primordial features; therefore, they might be used for the reconstruction of Archaean abiotic systems. peerReviewed

The quartz veins and pegmatites of the Sierra de Comechingones (Sierras de Cordoba, NE Argentina) belong to the Comechingones Pegmatite field (CPF). For the quartz veins and the zoned pegmatites related parental granites are missing. The country rock of the quartz veins are mylonitic augengneisses in granulite to upper amphibolite facies. Field relations, microscopy, cathodoluminescence, radiometric age data, fluid inclusion, chemical and isotopic composition and literature define the quartz veins as synorogenic formed during the high-temperature phase of the Famatinian (480–460 Ma) event. During the Famatinian up to the Achalian (382–366 Ma) event the synorogenic quartz veins were subjected to high temperature ductile deformation documented by folding, boudinage and finally brittle shearing. K-Ar ages of illite from the shear zones of about 166 Ma document the final cooling of the Sierras Pampeanas below 100 °C. The long lasting thermal and deformational history of the study area is reflected by very different populations of fluid inclusions in vein quartz with remarkably high contents of thermogenic hydrocarbons in the early-formed fluid inclusions. LA–ICP–MS analysis reveals very low lattice-bound trace element contents, i.e. high purity quartz.

Mineralogical and geochemical investigations of agates from Permian volcanic rocks of the Sub-Erzgebirge basin (Saxony, Germany) were made to constrain the genesis and characteristics of these spectacular forms of silica in acidic volcanic host rocks. Samples from the main agate occurrences of Chemnitz, Hohenstein-Ernstthal, St. Egidien and Zwickau were selected for detailed analyses. The results of the study show that agate formation can be related to volcanic activity (Rochlitz ignimbrite) and the subsequent alteration of the volcanic rocks. Most agates originate from the infill of silica into cavities of lithophysae (high-temperature crystallization domains), which formed during cooling of welded ignimbrite. Agate formation temperatures of probably > 150 °C were calculated from fluid inclusion and oxygen isotope studies, which indicate that the mobilization and accumulation of silica started already during a late phase of or soon after the volcanic activity. The trace-element composition of chalcedony and macrocrystalline quartz in agates is different from that of quartz from magmatic or metamorphic rocks and pegmatites. Elements of the volcanic rock matrix (Al, Ca, Fe, Na, K) were released during the alteration processes and accumulated in the SiO2 matrix of the agates. Extraordinary high contents of Ge (> 90 ppm), B (46 ppm) and U (> 18 ppm) were also detected, which can exceed the Clark concentration and sometimes the element concentration in the surrounding host rocks. In addition, chondrite-normalized REE distribution patterns of the agates show strong negative Eu-anomalies, enriched HREE as well as tetrad effects. These patterns are different from the REE patterns of the volcanic host rocks and point to fractionation processes during agate formation. The specific geochemical features indicate interactions of the host rocks with magmatic volatile fluids and heated meteoric water, and transport of SiO2 and other elements both in aqueous solution and via stable fluorine (and chlorine) compounds such as SiF4, BF3, GeF4, and UO2F2. The results of cathodoluminescence (CL) microscopy and spectroscopy revealed a microstructure of the agates that is similar for all occurrences. Characteristic features are irregular internal textures and sector zoning in quartz as well as luminescence colours and spectra, respectively, which are caused by a typical high defect density (oxygen vacancies, silanol groups). According to these results, the formation of agates can be explained by crystallization via an amorphous silica precursor under non-equilibrium conditions.

Silicified Agathoxylon -type wood of Late Palaeozoic age was characterized by means of cathodoluminescence (CL) and LA-ICP-MS of the quartz mass, which was found to contain wakefieldite, characterized by electron-microprobe (EMP) analysis, Raman microspectroscopy and X-ray diffraction. Although former organic matter is almost absent, plant anatomy served as the template for the quartz mass texture. Two generations of quartz mass were distinguished; the large proportion of the silicified wood consisting of brownish α-quartz with a dark reddish CL emission, and the minor portion of whitish ‘leached’ wood with a short-lived (transient) blue CL. On the outer edge, a silicified texture of formerly slightly humified wood also emits a dark reddish CL. Likely the wood specimen has been fossilized and diagenetically altered in several steps. The marginal part had been humified (reductively degraded) before the initial stages of silicification. The LA-ICP-MS analyses revealed chemical differences in all three distinct parts. The quartz mass relatively enriched in REEs and As and giving the dark reddish CL is interpreted as a primary diagenetic mineral mass. Whitish zones relatively depleted in U and V, and enriched in Al, Li, Rb, Cu, and Sr producing the blue CL would then be a secondary diagenetic overprint. An EMP/WDS analysis identified As-rich xenotime-(Y) and a solid solution of wakefieldite–(Ce) and wakefieldite–(Y), which locally enclose individual silicified tracheids. Wakefieldite, identified in silicified plant tissue for the first time, was most likely formed as a secondary mineral during post-depositional diagenesis. The mineral diagenesis did not erase the original anatomy of the wood.

Different quartz types from several localities in the Czech Republic and Sweden were examined by polarizing microscopy combined with cathodoluminescence (CL) microscopy, spectroscopy, and petrographic image analysis, and tested by use of an accelerated mortar bar test (following ASTM C1260). The highest alkali–silica reaction potential was indicated by very fine-grained chert, containing significant amounts of fine-grained to cryptocrystalline matrix. The chert exhibited a dark red CL emission band at ~640 nm with a low intensity. Fine-grained orthoquartzites, as well as fine-grained metamorphic vein quartz, separated from phyllite exhibited medium expansion values. The orthoquartzites showed various CL of quartz grains, from blue through violet, red, and brown. Two CL spectral bands at ~450 and ~630 nm, with various intensities, were detected. The quartz from phyllite displayed an inhomogeneous dark red CL with two CL spectral bands of low intensities at ~460 and ~640 nm. The massive coarse-grained pegmatite quartz from pegmatite was assessed to be nonreactive and displayed a typical short-lived blue CL (~480 nm). The higher reactivity of the fine-grained hydrothermal quartz may be connected with high concentrations of defect centers, and probably with amorphized micro-regions in the quartz, respectively; indicated by a yellow CL emission (~570 nm).

The occurrence and formation of silicified wood from five late Paleozoic basins in Central Europe was investigated. Fossil wood from diverse geological settings was studied using field observations, taphonomic determinations as well as mineralogical analyses (polarizing microscopy, cathodoluminescence (CL) microscopy and spectroscopy). The results indicate that silicification is either a monophase or multiphase process under varying physico-chemical conditions. In particular, CL studies revealed complex processes of silica accumulation and crystallization. The CL characteristics of quartz phases in silicified wood can mostly be related to blue (390 and 440 nm), yellow (580 nm), and red (650 nm) emission bands, which may appear in different combinations and varying intensity ratios. Yellow CL is typical for initial silicification, reflecting quick precipitation under oxygen-deficient conditions caused by initial decay of the organic material. Blue CL is predominantly of secondary origin, resulting from replacement of precursor phases by a secondary hydrothermal quartz generation or subsequent silicification of wood. The red CL can be related to a lattice defect (non-bridging oxygen hole center&mdash, NBOHC).

The origin of yellow cathodoluminescence (CL) in quartz has been investigated by a combination of CL microscopy and spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, and spatially resolved trace-element analysis by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The study shows that the appearance of a ~570 nm (2.17 eV) emission band can be attributed to high oxygen deficiency and local structural disorder in quartz. A proposed luminescence center model implies self-trapped exciton (STE) emission from localized amorphized regions in quartz. Although the high-intensity emission at 570 nm is in general consistent with high concentrations of E ′1 defects detected by EPR spectroscopy, CL studies with different electron beam parameters and annealing experiments up to 600 °C show a temperature and irradiation dependence of the luminescence related defects excluding the role of E ′1 centers as direct luminescence activators for the 570 nm emission. The evaluation of geochemical data shows that quartz with yellow CL occurs in low-temperature hydrothermal environment (mostly

Quartz samples of different origin from 10 localities in the Southern Ural region, Russia have been investigated to characterize their trace element compositions and defect structures. The analytical combination of cathodoluminescence (CL) microscopy and spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, and trace-element analysis by inductively coupled plasma mass spectrometry (ICP-MS) revealed that almost all investigated quartz samples showed very low concentrations of trace elements (cumulative concentrations of

Maximum Mesozoic transgressions flooded many continental areas worldwide, forming a wide and shallow seaway on the Iberian Microplate during the Late Cretaceous. Several siliciclastic and mixed siliciclastic–carbonate units developed along the Iberian Massif (cratonic area) while, at the same time, epeiric carbonate platforms spanned Iberia. These siliciclastic deposits unconformably cover the Variscan basement, as well as the Permian and Triassic deposits. This study focuses on sandstone provenance in central Spain, in a transgressive, relatively quiet tectonic setting with a wide rock variety in the potential source areas. Results shown in this paper can be applied in analogue systems; transgressive sandstones often form important hydrocarbon reservoirs due to their high primary porosity. The Cretaceous siliciclastic deposits are included in four formations ranging in age from the Cenomanian to the early Coniacian. The deposits were initially of fluvial origin, followed by a coastal-tidal setting. Quantitative petrographic analysis of sandstones from these formations reveals compositional variations related to provenance and weathering degree. The oldest formation (Utrillas Fm.) was deposited on a paleorelief surface. Sandstone composition changes from arkosic sandstones in the depressed area (Petrofacies P1a) to younger quartzarenites when sediments were deposited on top of the paleotopographic high (Petrofacies P1b). Quartz grains in both sub-petrofacies are angular to subangular, and the framework is poorly sorted. Intense weathering conditions are deduced for Petrofacies P1b, manifested by grain infiltration, clay coatings, and the absence of plagioclase grains and alteration features on K-feldspars. All these observations have been related to wetter conditions during P1b deposition. Main source areas of the Utrillas Fm were Ordovician metasediments and orthogneisses, Permian volcanic rocks, and Triassic Buntsandstein facies. Petrofacies 2 encompasses the three coastal-tidal formations, constituted mainly by subarkoses generally showing a subangular and poorly sorted framework. The deduced source areas are mainly associated with Variscan granitoids, pre-Ordovician schists and paragneisses, and Ordovician metasediments. Glauconite and carbonate grains support intrabasinal inputs. The low degree of sorting of this petrofacies related to a low-energy sedimentary environment produced lower values of original porosity compared to transgressive sandstone hydrocarbon reservoirs. Also, intrabasinal inputs promoted carbonate cementation and contribute to almost occlude the porosity., Funding for this research was provided by the Spanish Direcci´on General de Investigación Científica y T´ecnica (DIGICYT) projects CGL2011-22709 and CGL2014-52670-P and by the research group ‘‘Sedimentary Basin Analysis’’ UCM 910429 of the Complutense University of Madrid, and by the Geosciences Institute (IGEO-CSIC).

Materialien lassen sich vereinfacht grundsatzlich in 2 unterschiedliche Gruppen einordnen: Einkristalle und Keramiken. Einkristalle sind strukturell als Individuum anzusehen, Keramiken als polykristalline und oft als mehrphasige Aggregate. Trotz der einkristallinen Individualitat treten bei Einkristallen strukturelle Baufehler und/oder chemische Variationen auf, die entscheidend fur die Eigenschaften sind. Bei Keramiken, die aus vielen einkristallinen Individuen bestehen, kommen daruber hinaus noch Aspekte des Gefuges mit ins Spiel, die auch die Eigenschaften deutlich beeinflussen konnen. In diesem Kapitel wird die Basis fur das Verstandnis von Materialien korreliert mit den Eigenschaften gelegt.

Mineralische Rohstoffe sind durch geologische Prozesse gebildete, ausreichend erkundete und aufgrund ihrer Gebrauchseigenschaften nutzbare Bestandteile der Erde. Sie sind das Blut der Wirtschaft und stellen das Bindeglied zwischen den Geowissenschaften und den Ingenieurwissenschaften/Technik dar. Im Allgemeinen lassen sich die mineralischen Rohstoffe an Hand ihrer Eigenschaften und Einsatzkriterien in drei grose Gruppen einteilen: Energierohstoffe (z. B. Kohle, Erdol/Erdgas), Elementrohstoffe (z. B. Erze) sowie Eigenschaftsrohstoffe (z. B. Natursteine, Industrieminerale). Eine besondere Rolle spielen dabei die anorganisch-nichtmetallischen Eigenschaftsrohstoffe, auch oftmals als Steine, Erden und Industrieminerale bezeichnet. Fur eine optimale Nutzung dieser mineralischen Rohstoffe sind vor allem detaillierte Kenntnisse ihrer spezifischen Eigenschaften notwendig. Es wird ein Uberblick uber wichtige Steine, Erden und Industrieminerale wie z. B. Naturstein, Tonminerale, Quarzrohstoffe, Karbonate, Sulfate oder Edelsteine gegeben und an diesen Beispielen der Zusammenhang zwischen Mineraleigenschaften und technischer Nutzung diskutiert.