Calcite Crystals Research Articles

Origin of Zn-Pb Mineralization of the Vein Bt23C, Bytíz Deposit, Příbram Uranium and Base-Metal Ore District, Czech Republic: Constraints from Occurrence of Immiscible Aqueous–Carbonic Fluids

The mineralogical, fluid inclusion, and stable isotope (C, O) study was conducted on a Late Variscan Zn-Pb vein Bt23C, Příbram uranium and base-metal district, Bohemian Massif, Czech Republic. The vein is hosted by folded Proterozoic clastic sediments in exo-contact of a Devonian-to-Lower-Carboniferous granitic pluton. Siderite, dolomite-ankerite, calcite, quartz, baryte, galena, sphalerite, V-rich mica (roscoelite to an unnamed V-analogue of illite), and chlorite (chamosite) form the studied vein samples. The banded texture of the vein was modified by the episodic dissolution of earlier carbonates and/or sphalerite. Petrographic, microthermometric, and Raman studies of fluid inclusions proved a complicated fluid evolution, related to the activity of aqueous fluids and to an episode involving an aqueous–carbonic fluid mixture. Homogenization temperatures of aqueous inclusions decreased from ~210 to ~50 °C during the evolution of the vein, and salinity varied significantly from pure water up to 27 wt.% NaCl eq. The aqueous–carbonic fluid inclusions hosted by late quartz show highly variable phase compositions caused by the entrapment of accidental mixtures of a carbonic and an aqueous phase. Carbonic fluid is dominated by CO2 with minor CH4 and N2, and the associated aqueous solution has a medium salinity (6–14 wt.% NaCl eq.). The low calculated fluid δ18O values (−4.7 to +3.6‰ V-SMOW) suggest a predominance of surface waters during the crystallization of dolomite-ankerite and calcite, combined with a well-mixed source of carbon with δ13C values ranging between −8.2 and −10.5‰ V-PDB. The participation of three fluid endmembers is probable: (i) early high-temperature high-salinity Na>Ca-Cl fluids from an unspecified “deep” source; (ii) late low-salinity low-temperature waters, likely infiltrating from overlying Permian freshwater partly evaporated piedmont basins; (iii) late high-salinity chloridic solutions with both high and low Ca/Na ratios, which can represent externally derived marine brines, and/or local shield brines. The source of volatiles can be (i) in deep crust, (ii) from interactions of fluids with sedimentary wall rocks and/or (iii) in overlying Permian piedmont basins containing, in places, coal seams. The event dealing with heterogeneous CO2-bearing fluids yielded constraints on pressure conditions of ore formation (100–270 bar) as well as on the clarification of some additional genetic aspects of the Příbram’s ores, including the reasons for the widespread dissolution of older vein fill, the possible re-cycling of some ore-forming components, pH changes, and occasionally observed carbon isotope shift due to CO2 degassing.

Paleoclimatic and paleoenvironmental significance of late Pleistocene pedogenic carbonates (‘Caliche Cordão’) from the coastal Pampa of southern Brazil

The pedogenic carbonates found in Pleistocene units of the coastal Brazilian Pampa, informally designated as ‘Caliche Cordão', include rhizocretions, soft masses and isolated or coalescent nodules, either isolated within the sediment or forming discrete horizons, the most developed horizons (Ca-01 and Ca-02) stretching for hundreds of meters along the banks of Chuy Creek. Petrographic analyses show micritic (Alpha-type) matrix in most samples, with few signs of recrystallization as circumgranular spar rims or cracked sand grains. Stable carbon (δ13C) and oxygen (δ18O) isotope values in samples from the lower horizon Ca-01 exhibit small variation and indicate C3-dominated plant assemblages and carbonate precipitation from relatively 18O-enriched water, whereas the δ13C and δ18O in samples from the upper horizon (Ca-02) exhibit wider variation, higher proportion of C4 plants and precipitation from 18O-depleted water in some samples. The δ18O variations can be explained by variable degrees of evaporative enrichment, or to relative contributions of 18O-depleted (tropical) or 18O-enriched (subtropical) rainfall, based on the similarity with estimates from fossils of mastodons. Nodules from other sites are similar, but larger isotopic variations indicate carbonate precipitation at distinct times and environmental conditions, and a few exhibit partial recrystallization as larger spar calcite crystals. Luminescence ages of ∼74.7 and ∼71.3 ka of quartz grains in two nodules from Ca-01 indicate precipitation during MIS 4, whereas ages of ∼52 ka from Ca-02, and ≥30 ka in nodules from the shores of Mirim Lagoon indicate carbonate formation between MIS 3 and MIS 2. The probable source of carbonate was calcium released from eolian-sourced silty dust produced by Andean glaciers and transported from loess deposits in Argentina during cold and dry intervals of the last glacial, when arid/semiarid environments expanded from Patagonia across the Pampas up to southern Brazil. The variations of δ13C in calcretes formed between MIS 4 and 2 point to changes in plant assemblages that could have contributed for the local extinction of the mammalian megafauna.

Application of Blast Furnace Granulated Slag for Self-Healing Bio-Concretes

The properties of fine-grained concrete containing 20–80% granulated blast furnace slag and bacteria species Bacillus Subtilis have been studied. An assessment was made of changes in strength, self-healing of cracks using optical and electron microscopy and measuring the speed of ultrasound propagation perpendicular to the crack plane; composition and characteristics of the healing agent in cracks using X-ray analysis methods. Self-healing of cracks in concrete without bacteria occurred due to calcite deposition as a result of carbonation of portlandite during 50–65 cycles of humidification-drying, and in the presence of Bacillus Subtilis bacteria due to calcite deposition during their vital activity in 10–15 cycles. It is shown that the addition of granulated blast furnace slag slows down the crystallization of calcite, which forms a healing substance in the crack. It is assumed that the combined use of granulated blast furnace slag in dosages of 40–80% and Bacillus Subtilis bacteria in concrete structures operating under conditions of variable humidification can ensure the process of self-healing cracks and maintaining the strength of concrete in the long term due to simultaneous processes of strengthening the structure due to prolonged hydration of slag minerals and calcite deposition in cracks due to the vital activity of Bacillus Subtilis bacteria.

Multi-GW Peak Power Scaling in a Multi-pass Cell by Divided Pulse Scheme

Multi-pass cells, known for their efficient spectral broadening, currently face a challenge in their peak power scalability. To address this, we implemented a strategy where the input pulse was split into 8 replicas, resulting in an increased pulse energy following nonlinear compression. The used laser delivered 208 fs pulses at 1030 nm, with pulse energies reaching up to 140μJ. Using 3 calcite crystals, the input pulse was divided and passed through the MPC, achieving a spectral broadening down to a 40 fs bandwidth limit. Subsequently, the replicas were recombined using an identical set of crystals and compressed via chirped mirrors. FROG measurements revealed a duration of 43 fs. The recombination losses amounted to less than 5 % of the output energy. This method is particularly attractive and cost-effective for spectral broadening of ultrafast lasers with adjustable repetition rate.

A natural multifunction and multiscale hierarchical matrix as a drug-eluting scaffold for biomedical applications.

Sea urchin spines are biogenic single crystals of magnesium calcite that are stiff, strong, damage tolerant and light and have a bicontinuous porous structure. Here, we showed that the removal of their intraskeletal organic matrix materials did not affect the compressive mechanical properties and generated an open porosity. This matrix was able to adsorb and release oxytetracycline, a broad-spectrum antibiotic. The drug-loaded sea urchin matrix induced bacterial cell death after 4 and 8 hours of incubation of both Gram-negative E. coli and Gram-positive S. aureus strains and this process induces an inhibition of bacterial cell adhesion. In conclusion, this study shows that thermally treated sea urchin spines are a compressive resistant and lightweight matrix able to load drugs and with potential use in spine fusion, a challenging application that requires withstanding high compressive loading.

Remediation of Cd-polluted soil, improving Brassica napus L. growth and soil health with Hardystonite synthesized with zeolite, limestone, and green Zinc oxide nanoparticles

Acidic laterite may exhibit high cadmium (Cd) bioavailability and thus can cause potential environmental and human health hazards. We investigated the soil addition of zeolite (Ze), limestone (LS), and green synthesized zinc oxide nanoparticles (G-ZNPs) as sole soil additives, their mixture (LZ-Zn) and synthesized hardystonite {(S-Hyd), produced by calcination of all three additives}, to reduce Cd uptake and mitigate oxidative stress in Brassica napus L. (B. napus). Synthesis of hardystonite (S-Hyd) was confirmed by SEM, EDS, FTIR, and XRD and showed superior results than other additives for improving various parameters of plants and soil. Porous structure, larger surface area, alkaline properties, different functional groups (-OH, CO32−, Zn–O), and mineral crystals (cristobalite, calcite, zincite, and hardystonite) in S-Hyd facilitated Cd adsorption, reducing DTPA-Cd by 50%, compared to sole Cd polluted soil. S-Hyd enhanced soil enzymes and notably reduced Cd concentrations in plant roots and shoots by 59% and 78%, respectively, thereby decreasing the expression of Cd transport-related genes in plants. Interestingly, S-Hyd enhanced antioxidative defense, bioactive compounds, and photosynthetic pigments while lowering oxidative stress at molecular and physiological levels of plants. Economic comparison revealed that using S-Hyd was 87.0% more cost-effective than naturally occurring hardystonite (Hyd) to remediate Cd-polluted soil.

The solubility product controls the rate of calcite dissolution in pure water and seawater.

Quantification of calcite dissolution underpins climate and oceanographic modelling. We report the factors controlling the rate at which individual crystals of calcite dissolved. Clear, generic criteria based on the change of calcite particle dimensions measured microscopically with time are established to indicate if dissolution occurs under kinetic or thermodynamic control. The dissolution of calcite crystals into water is unambiguously revealed to be under thermodynamic control such that the rate at which the crystal dissolved is controlled by the rate of diffusion of ions from a saturated surface layer adjacent to the calcite surface. As such the dissolution rate is controlled by the true stoichiometric solubility product which is inferred from the microscopic measurement as a function of the concentration of NaCl. Comparison with accepted literature values shows that the role of ion pairing at high ionic strengths as in seawater, specifically that of CaCO3 and other ion pairs, exerts a significant influence since these equilibria control the amount of dissolved calcium and carbonate ions in the later of solution immediately adjacent to the solid.

Transport-Limited Growth of Coccolith Crystals.

Biogenic crystals present a variety of complex morphologies that form with exquisite fidelity. In the case of the intricate morphologies of coccoliths, calcite crystals produced by marine algae, only a single set of crystallographic facets is utilized. It is unclear which growth process can merge this simple crystallographic habit with the species-specific architectures. Here, a suite of state-of-the-art electron microscopies is used to follow both the growth trajectories of the crystals exsitu, and the cellular environment insitu, in the species Emiliania huxleyi. It is shown that crystal growth alternates between a space filling and a skeletonized growth mode, where the crystals elongate via their stable crystallographic facets, but the final morphology is a manifestation of growth arrest. This process is reminiscent of the balance between reaction-limited and transport-limited growth regimes underlying snowflake formation. It is suggested that localized ion transport regulates the kinetic instabilities that are required for transport-limited growth, leading to reproducible morphologies.

The decline of tufa deposition in an alkaline fen ecosystem in East-Central Europe and its impact on biotic assemblages: Insights from monitoring and paleoecological data

Protection and restoration of the CaCO3 depositing alkaline fens require an in-depth understanding of these unique and declining ecosystems. The present study investigates the development of the formerly heavy tufa depositing alkaline fen in East-Central Europe after CaCO3 precipitation markedly declined ca. 5400 cal yr BP. By combining palaeoecological and monitoring data, we aim to identify the limiting factors for tufa deposition and to recognise the vegetation and mollusc response to the change. Investigation of the current fen ecosystem included a botanical and malacological inventory and a monthly monitoring of the physicochemical properties of the groundwater emerging at the fen. It was also tested whether CaCO3 precipitates there. Transformations of the fen ecosystem since the mid-Holocene tufa decline were recognized by applying plant macrofossil and malacological analyses supplemented with organic matter and CaCO3 contents and the radiocarbon chronologies of the sediment cores. Although macroscopic tufa is currently not observed at the fen surface, the monitoring study revealed the microscopic calcite crystals at the glass slides during the spring and summer. A combination of cooling, gradual depletion of the Ca2+ pool, acidification of soils, and water table fluctuations was likely responsible for limiting tufa deposition in the mid-Holocene and maintaining this state during the late Holocene. Share of the calciphilous species' macrofossils (e.g. moss Tomentypnum nitens) declined following the sedimentary CaCO3 drop, whereas the contribution of species associated with high nutrient levels raised (e.g. Juncus articulatus). Inspection of the contemporary vegetation of the fen revealed that only Carex paniculata is associated with the calcium-rich substrate. The response of molluscs to the decline in tufa deposition remains unclear as mollusc shells did not preserve in CaCO3-depleted sediments, except for the youngest deposits. The present-day malacofauna consists of 21 species, including two rare and protected calciphilous species, namely Vertigo angustior and V. geyeri.

Dynamic quantitative phase imaging using calcite crystal-based temporally stable interferometer

This paper describes the development of a common path off-axis quantitative phase microscope (QPM), enabling high-speed quantitative measurements of sub-cellular dynamics in a live cell. The proposed 4f optical system consists of a polarizer, lenses, calcite crystal, pinhole and analyser, attached to the output port of an optical microscope converting it into a temporally stable QPM. The temporal phase stability of this optical configuration is measured to be equal to ∼20 mrad without a vibration isolation table. The utility of the microscope is demonstrated by conducting experiments on a polystyrene sphere (dia. 12 μm) and human red blood cells (RBCs). Furthermore, the developed system is implemented to study temporal membrane fluctuation in human RBCs over ∼30s and mouse embryonic fibroblast cell dynamics over 2 hours. Therefore, the system offers an energy-efficient and simple solution for generating object and reference beams for common-path QPM, making it an attractive alternative to existing approaches.

The mosaic tesserae in the industrial Byzantine wine press, Yavne, Israel: A natural unusually hard chalk or a chemically transformed chalk?

Many of the surfaces of a large industrial scale wine press from the Byzantine period in Yavne, Israel, are covered in mosaic tesserae. These surfaces are part of the grape presses, storage pools, fermentation pools and also the walkways between these structures. The calcitic tesserae resemble limestone in color, texture and fracture properties. We were therefore surprised to discover that they are more disordered at the atomic level than consolidated limestone and in fact they are as disordered as porous and friable chalk. In addition SEM examination of fracture surfaces reveals abundant nannofossils, mostly coccoliths and foraminifera; properties that are also reminiscent of chalk. The nanofossil identifications shows that the tesserae are from the Middle Eocene, and this includes the chalky Maresha Formation that outcrops about 15kms from the site. SEM examination of polished surfaces shows that the larger pores of tesserae are lined with euhedral calcite crystals. Vickers hardness measurements show that the tesserae are much harder than chalk, and are comparable to limestone. There are two scenarios for explaining these seemingly contradictory observations. One scenario is that a chalky limestone geological formation with all these properties exists somewhere in the Mediterranean region and is the source of the raw material for the tesserae. The second scenario is that the Byzantine constructors of the wine press transformed a chalk into a harder and more consolidated material. Chalk transformation processes akin to plaster formation can be excluded based on the analyses of the stable carbon isotopic compositions of the tesserae, as well as their 14C concentrations. A chemical transformation using a weak acid that would only affect the calcite in the vicinity of the accessible pores, and leave the bulk of the chalk and its microfossils in a good state of preservation, is conceivable. In fact a by-product of producing wine is vinegar and the acetic acid of the vinegar could conceivably have been used for this purpose. If indeed a chemical transformation of soft chalk into a hard durable material was used, this would represent a “lost” technology that might even be useful in present times.

Non-avian dinosaur eggshell calcite can contain ancient, endogenous amino acids

Proteins are the most stable of the macromolecules that carry genetic information over long periods of time. Closed systems are more likely to retain endogenous proteins or their degradation products. Amino acid racemisation data in experimental and subfossil material suggests that mollusc shell and avian eggshell calcite crystals can demonstrate closed system behaviour, retaining endogenous amino acids. Here, Late Cretaceous (Campanian–Maastrichtian) Argentine titanosaurian sauropod eggshells show dark, organic stains under light microscopy/photography and fluorescence imaging. Raman spectroscopy can yield bands consistent with various organic molecules, possibly including N-bearing molecules or geopolymers. Pyrolysis-gas chromatography-mass spectrometry reveals pyrolysates consistent with amino acids as well as aliphatic hydrocarbon homologues that are not present in modern eggshell, consistent with kerogen formation deriving from eggshell lipids. High-performance liquid chromatography reveals that their intra-crystalline fraction can be enriched in some of the most stable amino acids (Glx, Gly, Ala, and possibly Val) and are fully racemic (despite being some of the slowest racemising amino acids), indicating ancient origin. This preservation varies across localities, but similar ancient amino acid profiles were also observed in Late Cretaceous Spanish titanosaurians from several localities and Chinese putative hadrosaurid eggshell. These amino acid results are consistent with previous studies on degradation trends deduced from modern, thermally matured, sub-fossil, and ∼3.8–6.5 Ma avian eggshell, as well as ∼30 Ma calcitic mollusc opercula. Selective preservation of certain fully racemic amino acids, which do not racemise in-chain, and the concentration of free amino acids suggests likely complete hydrolysis of original peptides. Liquid chromatography-tandem mass spectrometry supports this hypothesis by failing to detect any non-contamination peptide sequences from the Mesozoic eggshell. These closed-system amino acids are possibly the most thoroughly supported non-avian dinosaur endogenous protein-derived constituents, at least those that have not undergone oxidative condensation with other classes of biomolecules. Biocrystal matrices can help preserve mobile organic molecules by trapping them (perhaps with the assistance of resistant organic polymers), but trapped organics are nevertheless prone to diagenetic degradation, even if such reactions might be slowed in exceptional circumstances. Future work should survey fossil biocalcite to determine variability in amino acid preservation.

Microbialites on the northern shelf of Lake Van, eastern Türkiye#: Morphology, texture, stable isotope geochemistry and age

ABSTRACTLake Van, the world's largest alkaline lake, hosts some of the largest microbialite towers worldwide, which are considered as modern analogues of ancient stromatolites. This study investigates the links between microbialite evolution, geology, climate and hydrology, and the role of biotic and abiotic processes in microbialite growth and morphology. For these objectives, the northern shelf of Lake Van was surveyed by sub‐bottom seismic profiling and diving, and two 9 m and 15 m high microbialite chimneys were sampled at 25 m water depth. Samples were analysed for stable oxygen and carbon isotopes, X‐ray diffractometry, scanning electron microscopy and U/Th age dating. Lake Van microbialites precipitate wherever focused Ca‐rich groundwater flows onto the lake floor to mix with alkaline lake water. Variable columnar, conical and branching morphologies of the microbialites indicate various processes of formation by groundwater channelling within the chimneys. Collectively, our data suggest that the microbialite chimneys have formed within the last millennium, most likely starting during the warm and humid Medieval Climate Anomaly (ca ad 800–1300), when lake level rose approximately to the present level due to enhanced Inputs of riverine Ca‐rich freshwater and groundwater. Our new scanning electron microscopy observations indicate that the internal structure of the microbialites below the outer cyanobacteria‐covered crust is constructed by calcified filaments, globular aggregates and nanocrystals of algal, cyanobacterial and heterobacterial origins and inorganically precipitated prismatic calcite crystals. These textural features, together with dive observations, clearly demonstrate the important role of inorganic carbonate precipitation at sites of groundwater discharge, followed by cyanobacteria and algal mucilage deposition and microbially meditated calcification in the photic zone in the rapid growth of the microbialite chimneys. Considering the close similarities of some textures with those of ancient stromatolites and meteorites, the results of this study provide new insights into the environmental conditions associated with stromatolite formation and extra‐terrestrial life evolution.

Fluid Regime of Crystallization of the Calcite–Quartz Carbonatitoids of the Murun Massif

Abstract —Primary melt and fluid inclusions in quartz and dalyite of calcite–quartz carbonatitoids of the Murun massif have been studied. They contain CO2, N2, CH4, C2H6, C3H8, H2, and H2S as well as sulfates and hydrocarbonates as solid daughter phases. The inclusion solutions contain HS- and chlorides. In addition, disordered carbon and bitumen are present. It is concluded that the magmatic fluid phase that was in equilibrium with quartz was characterized by a predominantly H2O–CO2–H2S composition and a reduced state. This explains the appearance of sulfides at the magmatic stage of crystallization of calcite–quartz carbonatitoids of the Murun massif. We substantiate the hypothesis that the sulfates, hydrocarbons, and H2 detected in the inclusions form at decreasing temperature as a result of shift of the redox equilibrium.

Biotic-Abiotic Radial-Acicular Crystal Fan Fabrics with Rosickýite at the Angel Springs Tufa-Travertine Deposit in Southern British Columbia

Abstract The tufa-travertine deposit at Angel Springs developed through the interaction of thermal waters with bedrock of the Proterozoic Okanagan Gneiss, which extends along the eastern margin of the Okanagan Valley fault system in south-central British Columbia. This warm spring is proximal to Miocene plateau basalt flows that cut the Okanagan Gneiss bedrock eastward of the Okanagan Valley. The carbonate deposit, which is widely referenced as tufa, consists of a tufa and an overlying travertine. These texturally and petrographically different deposits developed in response to a shift in the groundwater pathway wherein the surface discharge transitioned from multiple vents of the tufa to a single downslope vent pool of the overlying travertine. Lower interval tufa fabrics are characterized by networks of fenestral-type porosity supported by a framework of curvilinear stromatolitic sheets of calcite that resulted from the partial coalescence of sub-horizontal arrays of calcite-encrusted cyanobacteria. These tufa fabrics aligned with the strong stream flow emanating from multiple vents. In contrast, radial crystal fan fabrics of the upper interval travertine developed with the transition from biotic calcite encrustations of upward branching cyanobacteria to the abiotic development of radial crystal fans. Length-long mouldic porosity tubules were occluded as the abiotic sheaf- and fan-shaped crystal growth surfaces expanded radially with rapid degassing. Core areas of the radial crystal arrays coalesced and were partially recrystallized, resulting in spheroidal crystalline fabrics that preserve inclusion-delineated concentric growth surfaces. Syntaxial overgrowths of radially aligned acicular crystals rapidly expanded from these core areas of coalesced calcite, resulting in the formation of abiotic radial-acicular and starburst crystal arrangements. The biotic–abiotic transition resulted in the rapid growth of abiotic crystal fans as the dominant deposition process of the upper interval travertine fabrics, but not in the lower interval tufa fabrics. Activities of sulfate-reducing bacteria in the sulfate-rich thermal water of both intervals resulted in precipitation of rosickýite, the monoclinic polymorph of S, as nanocrystalline globular protuberances on surfaces of calcite crystals. This is the first recorded occurrence of rosickýite in a tufa-travertine deposit and the first recognition of this mineral in Canada.

Exploring the Potential of Polypropylene Fibers and Bacterial Co-Culture in Repairing and Strengthening Geopolymer-Based Construction Materials

This study explored self-healing in geopolymer mortar cured at ambient temperature using polypropylene fibers and bacterial co-cultures of Bacillus subtilis and Bacillus megaterium. Damage degree, compressive strength, ultrasonic pulse velocity (UPV), strength-regain percentage, and self-healing percentage were evaluated. A full factorial design was used, which resulted in an eight-run complete factorial design with four levels in the first factor (polypropylene content: 0%, 0.25%, 0.5%, and 0.75%) and two levels in the second factor (bacteria concentration: 0 (without) and 1 (with)). The results indicate that increasing the polypropylene fiber content enhanced strength regains up to 199.97% with 0.75% fibers and bacteria. The bacteria alone improved strength-regain percentages by 11.22% through mineral precipitation. The analysis of variance (ANOVA) showed no interaction between fibers and bacteria, but both independently improved the compressive strength. Only bacterial samples exhibited positive self-healing, ranging from 16.77 to 147.18%. The analysis using a scanning electron microscope with energy dispersive X-ray (SEM-EDX) and X-ray fluorescence (XRF) also revealed greater calcite crystal formation in bacterial samples, increasing the strength-regain and self-healing percentages. The results demonstrate that polypropylene fibers and bacteria cultures could substantially enhance the strength, durability, and self-healing percentage of geopolymer mortars. The findings present the potential of a bio-based self-healing approach for sustainable construction and repair materials.

Study of synergistic effect of fly ash and superabsorbent polymers on properties of cement pastes

The main goal of this study is to observe changes in microstructural properties and the mutual interaction of cement pastes containing superabsorbent polymers (SAPs) and fly ash. SAP is a type of hydrogel additive, able to absorb large amounts of liquid in its structure. In cement-based materials, it is often used in the early stages of matrix hydration to absorb excess mixing water and to release it in the later stages, which is even more desirable when the material is exposed to higher temperatures. Another research goal is a partial substitution of binder (Portland cement) by the energy by-product of high-temperature ash, produced by the combustion of brown coal. A further goal is the observation of the interactions of these binders with the SAPs on the microstructural scale. For this purpose, computed tomography (CT), X-ray diffraction (XRD), differential thermal analysis (DTA), and scanning electron microscopy (SEM) were performed. Basic physical and mechanical properties such as compressive strength, flexural strength, and bulk density were also determined. In the early stages of hydration, viscosity and chemical shrinkage were determined. From the results obtained, it is obvious that the presence of SAPs has a significant impact on the properties of cement pastes. From the two tested SAPs, SAP HM has a positive effect on volume stability and the flexural strength of the composite. The results of the mineralogical composition showed that the effect of SAP incorporation influences the crystallization of portlandite, alite, belite, and calcite. SEM analysis confirmed the results of XRD analysis and proved that hydration products can grow into SAP cavities. It is clear from the evaluation of the pore structure that SAPs increase the porosity of cement composites. The admixture of high-temperature fly ash has a positive effect on reducing the volumetric changes of mixtures. The mechanical parameters of the composite with fly ash were similar to that of the reference test specimens.

Tailoring CaCO3 microstructure to improve trace phosphate removal from water

The phosphorus raw material is in crisis, and the demand for P-fertilizer production is increasing, therefore different sources are sought. The trace concentration of phosphorus in treated domestic wastewater is a potential point of recovery as an alternative source of phosphate solids. In this study, we synthesized CaCO3 with a specific microstructure with an enhanced kinetics for the removal of trace concentrations of phosphate from a model solution. The crystalline morphology of the materials was tailored by the addition of organic additives into the CaCO3 precipitation solution. We synthesized CaCO3 by mixing Na2CO3 and CaCl2 water solutions and different concentrations of citrate (from 3 to 152 mM, equal to 1.2, 11.3 and 50.6 % citrate/Ca2+) as morphology modifiers. Samples were characterized by SEM, TEM, XRD, and nitrogen physisorption. The crystalline structure of all materials corresponds to calcite crystals; however three main properties: the crystalline habit, crystallite size, and surface area, change in function of the citrate concentration used in the synthesis. Particularly, CaCO3 synthesized in a 50 % citrate/Ca2+ (sample C3) consists of agglomerates of porous peanut-shaped calcite crystals, with a crystallite size of 28 nm, and a surface area of 29.8 m2/g. Selected samples were tested for the removal of phosphate from water in batch and column experiments. In batch experiments, sample C3 was able to reduce 80 % of the phosphate within minutes from a solution with an initial concentration of 2.4 mg P/L, using a CaCO3 dose of 1.3 g/L. Sample C3 was tested for the removal of phosphate in a fluidized bed column system. The spent material showed calcium phosphate precipitates as verified by XRD characterization, revealing a surface precipitation removal mechanism.

Stomiosphaerina bakae sp. nov., a new calcareous dinocyst of the Upper Cretaceous of the Central European Basin.

In this work the new species of Stomiosphaerina bakae sp. nov. is described. This is the third species of the genus Stomiosphaerina. Several dozen specimens of the newly described species were found within the Upper Cretaceous (upper Turonian) white chalk at Dubivtsi section near Halych in western Ukraine (south-eastern margin of Central European Basin). Stomiosphaerina bakae sp. nov. has an asymmetrical oval (pear-like shape) test, as it is wider in one side, and sharp in the opposite side, ranging from 55 to 67 μm in length and from 42 to 56.5 μm in width. It has a two-layered calcareous test. The outer layer, with thickness ranging from 4.5 to 6.5 μm, is built of long and wide plate-shaped calcite crystals and is white in plain-polarized light with a dark cross in crossed-polarized light. The inner layer, with thickness ranging from 1.5 to 4.5 μm, is yellowish, goldish to brownish color in plain-polarized light, with proximal and distal side smooth and even, and is built of short fibrous calcite crystals, without preferential orientation. One narrow (6 to 8 μm width) aperture is observed. Stomiosphaerina bakae sp. nov. differs from other species of Stomiosphaerina, i.e. Stomiosphaerina biedai Nowak 1974 and Stomiosphaerina proxima Řehánek 1987, by its cyst-shape, cyst-size, layers thickness, structure of outer layer and width of aperture. Stomiosphaerina bakae sp. nov. most likely corresponds to the non-defined species of Stomiosphaerina sp. described by Nowak 1974.

Light-driven nucleation, growth, and patterning of biorelevant crystals using resonant near-infrared laser heating

Spatiotemporal control over crystal nucleation and growth is of fundamental interest for understanding how organisms assemble high-performance biominerals, and holds relevance for manufacturing of functional materials. Many methods have been developed towards static or global control, however gaining simultaneously dynamic and local control over crystallization remains challenging. Here, we show spatiotemporal control over crystallization of retrograde (inverse) soluble compounds induced by locally heating water using near-infrared (NIR) laser light. We modulate the NIR light intensity to start, steer, and stop crystallization of calcium carbonate and laser-write with micrometer precision. Tailoring the crystallization conditions overcomes the inherently stochastic crystallization behavior and enables positioning single crystals of vaterite, calcite, and aragonite. We demonstrate straightforward extension of these principles toward other biorelevant compounds by patterning barium-, strontium-, and calcium carbonate, as well as strontium sulfate and calcium phosphate. Since many important compounds exhibit retrograde solubility behavior, NIR-induced heating may enable light-controlled crystallization with precise spatiotemporal control.