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Control over the shape and morphology of single crystals is a theme of great interest in fundamental science and for technological application. Many synthetic strategies to achieve this goal are inspired by biomineralization processes. Indeed, organisms are able to produce crystals with high fidelity in shape and morphology utilizing macromolecules that act as modifiers. An alternative strategy can be the recovery of crystals from biomineralization products, in this case, seashells. In particular, waste mussel shells from aquaculture are considered. They are mainly built up of single crystals of calcite fibers and aragonite tablets forming an outer and an inner layer, respectively. A simple mechanochemical treatment has been developed to separate and recover these two typologies of single crystals. The characterization of these single crystals showed peculiar properties with respect to the calcium carbonate from quarry or synthesis. We exploited these biomaterials in the water remediation field using them as substrate adsorbing dyes. We found that these substrates show a high capability of adsorption for anionic dye, such as Eosin Y, but a low capability of adsorption for cationic dyes, such as Blue Methylene. The adsorption was reversible at pH 5.6. This application represents just an example of the potential use of these biogenic single crystals. We also envision potential applications as reinforcing fillers and optical devices. published

Aragonite, one of the most common biological calcium carbonate minerals, is widespread in marine plankton and neritic sediments (e.g., accounting for 89% of pelagic calcification of CaCO3 in the surface ocean). Its dissolution directly affects the export fluxes of CaCO3 in seawater. The aragonite dissolution in the ocean correlates with the increase of partial pressure of carbon dioxide and is pertinent to acidic biomolecules. However, aragonite dissolution in seawater with acidic biomolecules has been overlooked, and the interaction mechanism is unclear. In-situ atomic force microscopy (AFM) was employed to observe the dissolution features of aragonite (110) growth surfaces in succinic acid (SUC, HOOC-CH2-CH2-COOH) solutions. The results demonstrate that (1) both the morphologies and spreading rates of the etch pits formed on aragonite (110) surfaces are altered by the interactions between SUC molecules and the surfaces; (2) the [1-11] and [-111] steps of the etch pits on aragonite (110) surfaces in SUC solutions are kinetically controlled; (3) dissolution rates of aragonite (110) surfaces are proportional to SUC concentrations, which is attributed to the strong complexation between SUC molecules and surface-bounded Ca atoms (≡Ca+); (4) etch pits morphologies of aragonite (110) and calcite (10.4) surfaces are different in SUC solutions, and the spreading rates of the etch pits of the former are one to two orders of magnitude lower than those of the latter. Furthermore, aragonite is found to be more sensitive to SUC molecules than calcite, suggesting that dissolving aragonitic materials could be more easily affected by circumambient biomolecules than dissolving calcitic materials. In seawater that contains organic molecules, the dissolution fluxes of aragonite could be much slower than those of calcite. These findings not only reveal the site-specific interactions between SUC molecules and the ≡Ca+ on aragonite (110) surfaces but also emphasize its implication for the oceanic aragonite dissolution fluxes.

Marine bivalve mollusc shells can offer valuable insights into past oceanographic variability and seasonality. Given its ecological and archaeological significance, Mytilus californianus (California mussel) presents the opportunity to examine seasonal and decadal changes recorded in its shell over centuries to millennia. While dark–light growth bands in M. californianus shells could be advantageous for reconstructing past environments, uncertainties remain regarding shell structure, environmental controls of dark–light band formation, and the amount of time represented by a dark–light pair. By analyzing a suite of M. californianus shells collected in 2002, 2003, 2019, and 2020 from Bodega Bay, California, we describe the mineralogical composition, establish relationships among growth band pattern, micro-environment, and collection season, and compare shell structure and growth band expression between the archival (2002–2003) and modern (2019–2020) shells. We identified three mineralogical layers in M. californianus: an outer prismatic calcite layer, a middle aragonite layer, and a secondary inner prismatic calcite layer, which makes M. californianus the only Mytilus species to precipitate a secondary calcite layer. Within the inner calcite layer, light bands are strongly correlated with winter collection months and could be used to reconstruct periods with moderate, stable temperatures and minimal upwelling. Additionally, modern shells have significantly thinner inner calcite layers and more poorly expressed growth bands than the archival shells, although we also show that growth band contrast is strongly influenced by micro–environment. Mytilus californianus from northern California is calcifying differently, and apparently more slowly, than it was 20 years ago.

The rapid retreat of the Dead Sea during the past four decades led to the exposure of unique structures of massive gypsum along the shores. Many of these structures (having the shape of mounds) are associated with the activity of Ein Qedem-type saline springs that currently discharge Ca-chloride brine to the lake. Field observations, radiocarbon dating of aragonite (within the gypsum mounds) that yield ancient ages, and the narrow range of δ34S and δ18O values ( δ 34 S gyp : 14.1–16.9‰; δ 18 O gyp : 14.4–16.5‰) indicates that the formation of the gypsum structures is related to the mixing of brines: the Dead Sea brine and ancient (last glacial) Ein Qedem type brine. These are Ca-chloride brines having different salinities and sulfur concentrations that satisfy conditions of an outsalting process whereby supersaturation of gypsum is attained by the mixing of these two brines in the offshore shallow water environment. Thermodynamic calculations (using the PHREEQC software) show that gypsum outsalting occurred when both brines were enriched with sulfate as compared to the present. The Ein-Qedem brine had higher sulfate when subjected to less intensive bacterial sulfate reduction. The Dead Sea was characterized by higher sulfate concentrations during intervals of low lake stands. The conditions of higher sulfate concentrations and enhanced discharge of the saline springs occurred repeatedly in the Dead Sea between ∼6.6 to 0.6 ka and were intermittent with periods of enhanced supply of sulfate to the lake by freshwaters.

Corals nucleate and grow aragonite crystals, organizing them into intricate skeletal structures that ultimately build the world’s coral reefs. Crystallography and chemistry have profound influence on the material properties of these skeletal building blocks, yet gaps remain in our knowledge about coral aragonite on the atomic scale. Across a broad diversity of shallow-water and deep-sea scleractinian corals from vastly different environments, coral aragonites are remarkably similar to one another, confirming that corals exert control on the carbonate chemistry of the calcifying space relative to the surrounding seawater. Nuances in coral aragonite structures relate most closely to trace element chemistry and aragonite saturation state, suggesting the primary controls on aragonite structure are ionic strength and trace element chemistry, with growth rate playing a secondary role. We also show how coral aragonites are crystallographically indistinguishable from synthetic abiogenic aragonite analogs precipitated from seawater under conditions mimicking coral calcifying fluid. In contrast, coral aragonites are distinct from geologically formed aragonites, a synthetic aragonite precipitated from a freshwater solution, and mollusk aragonites. Crystallographic signatures have future applications in understanding the material properties of coral aragonite and predicting the persistence of coral reefs in a rapidly changing ocean.

Ooids (subspherical particles with a laminated cortex growing around a nucleus) are ubiquitous in the geological record since the Archean and have been widely studied for more than two centuries. However, various questions about them remain open, particularly about the role of microbial communities and organic matter in their formation and development. Although ooids typically occur rolling around in agitated waters, here, we describe for the first time aragonite ooids forming statically within microbial mats from hypersaline ponds of Kiritimati (Kiribati, central Pacific). Subspherical particles had been previously observed in these mats and classified as spherulites, but these particles grow around autochthonous micritic nuclei, and many of them have laminated cortices, with alternating radial fibrous laminae and micritic laminae. Thus, they are compatible with the definition of the term ‘ooid’ and are in fact very similar to many modern and fossil examples. Kiritimati ooids are more abundant and developed in some ponds and in some particular layers of the microbial mats, which leads to the discussion and interpretation of their formation processes as product of mat evolution, through a combination of organic and environmental factors. Radial fibrous laminae are formed during periods of increased supersaturation, either by metabolic or environmental processes. Micritic laminae are formed in closer association with the mat exopolymer (EPS) matrix, probably during periods of lower supersaturation and/or stronger EPS degradation. Therefore, this study represents a step forward in the understanding of ooid development as influenced by microbial communities, providing a useful analogue for explaining similar fossil ooids.

ACKNOWLEDGEMENTS The authors would like to thank the following bodies for funding this research: Shell Brazil through the ‘BG05: UoA-UFRGS_SWB Sedimentary Systems’ project at UFRGS, the Aberdeen Formation Evaluation Society and the University of Aberdeen. LAMIR, BGS and EPMA staff are also thanked for their assistance with stable isotope and electron microprobe analysis. Dr Ilse Kamerling and Dr. D. Kemp are thanked for their assistance with pXRF analysis, Marianna Skupinska with collection of point count data and Prof. D. McIlroy is thanked for his assistance during fieldwork. Reviews by Dr C. Pederson, Prof. P. Swart and two anonymous reviewers helped improve the manuscript significantly.

Trepostome bryozoan skeletalisation did not passively respond to changes in seawater chemistry associated with calcite-aragonite seas. According to Stanley and others, trepostome bryozoans were passive hypercalcifiers. However, if this was the case, we would expect their degree of calcitic colony calcification to have decreased across the Calcite I Sea to the Aragonite II Sea at its transition in the Middle Mississippian. Data from the type species of all 184 trepostome genera from the Early Ordovician to the Late Triassic were utilised to calculate the Bryozoan Skeletal Index (BSI) as a proxy for the degree of calcification. BSI values and genus-level diversity did not decrease across the transition from the Calcite I Sea to the Aragonite II Sea. Nor were there any changes in the number of genus originations and extinctions. This suggests that trepostome bryozoans were not passive hypercalcifiers but active biomineralisers that controlled the mineralogy and robustness of their skeletons regardless of changes in seawater chemistry.

Dolomite is a predominantly diagenetic mineral that forms by replacing marine calcite and aragonite during burial. Dolomitization requires subsurface fluid flow to deliver Mg and remove product Ca, and only forms abiotically in laboratory experiments at temperatures above ~100°C, equivalent to burial depths of 3 km or greater. Limited sources of Mg at these depths would appear to restrict most dolomite formation to shallow burial depths using seawater as a source of reactive Mg, despite the kinetic limitation imposed by lower temperatures. The Williston Basin is replete with evaporites and dolomites that appear to have formed using Mg from evaporatively concentrated seawater at near surface temperatures. However, two dolomite bodies examined in this study record basin wide gradients in 87Sr/86Sr ratios and δ26Mg values that are inconsistent with dolomitization by seawater. We evaluate the processes that may have created these gradients. We propose a model whereby seepage reflux created early diagenetic protodolomite that was later altered during deep burial by 87Sr and Mg-enriched fluids ascending from the deep structural center of the basin with the degree of alteration decreasing towards the edges. The ascending fluid flow event is tentatively linked to anomalous heating in the Late Devonian / Early Carboniferous. Vertical faults are hypothesized to have behaved as conduits for channeling 87Sr and Mg-enriched crustal fluids upwards into the bottom of the Williston Basin, pressurizing the basal aquifer system and commencing up-dip directed fluid flow through confined aquifers. Clumped isotope and fluid inclusion thermometry indicate that the ascending fluids were hydrothermal with an estimated δ26Mg value of –0.65 ±0.20‰, which is much lower than estimates of early Paleozoic seawater δ26Mg values of +0.09 to +0.23‰. Two sources of crustal Mg are consistent with the low inferred δ26Mg values of the ascending fluid: (1) chlorite, which preferentially releases isotopically light Mg, with literature values in the range of –0.78‰ to –1.8‰, and (2) magnesite, which forms during carbonation of serpentinite with literature values in the range –0.7‰ to –1.1‰. Ultramafic rocks belonging to the Thompson Nickel Belt pass beneath the center of the Williston Basin in North Dakota, indicating that dissolution of both chlorite and magnesite may have contributed reactive Mg to the Williston Basin during the ascending fluid flow event. As dolomite is a mineral that is easily altered during burial, our findings warrant caution in choosing dolomites for reconstructing the 26Mg history of seawater.

Objective: This in-vitro study evaluated the remineralizing effect of nano-pearl and nano-seashell incorporated into fluoride-based pits-and-fissures sealants by assessing the enamel surface microhardness and the enamel elemental analysis. Materials and Methods: 75 extracted third molars were randomly allocated to one of the following 5 groups of fluoride containing sealant: 10% nano-pearl; 15% nano-pearl; 10% nano-seashell; 15% nano-seashell; or plain fluoride containing sealant. After 2 weeks of dynamic pH-cycling using Pepsi as demineralizing solution; 10 molars of each group were subjected to microhardness assessment, while 5 molars of each group were subjected to Energy Dispersive X-ray Analysis. Results: Teeth treated with 15% nano-pearl reported the highest percentage increase (20.5%) while teeth treated with plain fluoride containing sealant showed a percentage decrease (-11.62 %). The XRD pattern results confirmed the presence of aragonite and calcite polymorphs of CaCO3 in nano-pearl powder and the presence of aragonite in nano-seashell powder. Calcium ions recorded a significantly higher value in the groups treated with 10% and 15% nano-pearl incorporated pits and fissure sealant. Conclusion: The incorporation of 10 % and 15 % nano-pearl and nano-seashell particles into fluoride-based pits and fissure sealant significantly improved the enamel surface microhardness as well as the enamel mineral content.

Calcium carbonate-based bone substitutes derived from natural coral exoskeleton (aragonite) are resorbed and remodeled faster than calcium phosphate-based substitutes. However, coral species with structures appropriate for use as bone substitutes are very limited. Therefore, it is important to evaluate potential of artificial calcium carbonate ceramics as a bone substitute. In this study, calcium carbonate granules with various porosities and pore sizes were prepared by sintering a highly pure (>99.98%) calcium carbonate powder (calcite), and their resorption properties and bone formation abilities were examined in vivo for the first time. The sintered calcium carbonate was resorbed faster than β-tricalcium phosphate, which has a similar structure. However, sintered calcium carbonate did not promote new bone formation during long-term implantation. Furthermore, both resorption and new bone formation were affected by the pore structure. The optimal structures of the artificially sintered calcium carbonate bone substitute were also discussed.

Aragonite Twins that appear to be hexagonal prisms are classic mineral specimens found in many locations around the world, but they are particularly well known from Molina de Aragon and Minglanilla...

Eight SrxCa1−xCO3 (0.2 strontianite > witherite > cerussite. The vibrational contribution to the excess Gibbs free energy is constrained for the SrxCa1−xCO3 solid solution, whose miscibility gap shrinks at elevated temperatures and disappears above ~400 K. The calculated equilibrium Sr-Ca exchange coefficient ( K D Sr / C a ) between aragonite and seawater is systematically lower than the measured ones below ~80 °C, suggesting kinetic control on Sr partitioning at low temperatures. We also evaluate the metal cation effect on the carbon and oxygen isotope fractionations between aragonite-group carbonates and CO2 or H2O. Our results show that the 1000∙lnβ (where β is the reduced partition function ratio) for both carbon and oxygen isotope fractionations decrease linearly with increasing average atomic mass of the divalent cation in these aragonite-group carbonates, and the compositional effect on isotope fractionations can be treated as a linear function of Sr2+ concentration in the SrxCa1−xCO3 solid solution.

The capability of Time of Flight-Secondary Ion Mass Spectrometry (ToF-SIMS) of analysing molecular archaeal biomarkers in geobiological samples was tested and demonstrated. Using a bismuth cluster primary ion source, isopranyl glycerol di- and tetraether core lipids were detected in small amounts of total organic extracts from methanotrophic microbial mats, simultaneously and without further chemical treatment and chromatographic separation. ToF-SIMS was also employed to track the distribution of fossilized ether lipids in a massive carbonate (aragonite) microbialite that precipitated as a result of the microbial anaerobic oxidation of methane. An unambiguous signal was obtained when analysing a freshly broken rock surface (base of a microdrill core). Though some limitation occurred due to pm-topographical effects (sample roughness), it was possible to display the abundance of high molecular weight (C-86) of tetraethers exposed in particular regions of the rock surface. 'Molecular mapping' revealed that a part of these molecules was encased within the rock fabric in a cluster-like distribution that might trace the arrangement of the calcifying microbial colonies in the once active mat system. The results reveal promising perspectives of ToF-SIMS for (i) the quasi- nondestructive analysis of lipids in extremely small geobiological samples at low concentrations; (ii) resolving the spatial distribution of these compounds on a mu M2- to cm(2)-scale; and (iii) the more exact assignment of lipid biomarkers to their biological source.

The oceans play a major role in the earth’s climate by regulating atmospheric CO2. While oceanic primary productivity and organic carbon burial sequesters CO2 from the atmosphere, precipitation of CaCO3 in the sea returns CO2 to the atmosphere. Abiotic CaCO3 precipitation in the form of aragonite is potentially an important feedback mechanism for the global carbon cycle, but this process has not been fully quantified. In a sediment-trap study conducted in the southeastern Mediterranean Sea, one of the fastest warming and most oligotrophic regions in the ocean, we quantify for the first time the flux of inorganic aragonite in the water column. We show that this process is kinetically induced by the warming of surface water and prolonged stratification resulting in a high aragonite saturation state (ΩAr ≥ 4). Based on these relations, we estimate that abiotic aragonite calcification may account for 15 ± 3% of the previously reported CO2 efflux from the sea surface to the atmosphere in the southeastern Mediterranean. Modelled predictions of sea surface temperature and ΩAr suggest that this process may weaken in the future ocean, resulting in increased alkalinity and buffering capacity of atmospheric CO2.

Contributions of abiotic and biotic processes on travertine deposition are still not well understood due to technical difficulties, despite that the travertines draw attention as analogues for ancient microbial carbonates and oil reservoirs. To evaluate their contributions, this study examined eight hot springs in Japan. Water chemistry analyses showed common downstream trends: a decrease in CO2 concentration and increases in CO32− concentration and pH. Mineralogical analysis showed that the constituent minerals of travertines at six hot springs were both calcite and aragonite, while one was just calcite and another only aragonite. Microscopic observations of travertine surfaces indicated the dominance of cyanobacteria secreting extracellular polymeric substances without a detectable amount of carboxyl groups. Small particles were sometimes entangled/covered by these cyanobacteria. Microelectrode measurements showed the occurrence of abiotic CaCO3 precipitation and photosynthetic induction/inhibition of CaCO3 precipitation, of which extent was different at each site. By integrating these results, the contributions of abiotic and biotic processes were evaluated. Cyanobacteria inhabiting on travertine surfaces were generally not calcified regardless of an ambient high CaCO3 saturation state; instead, they contributed to creating pore spaces and trap/bind suspended particles. Downstream CO2 degassing increased the CaCO3 saturation state by shifting carbonate chemical equilibrium and caused abiotic CaCO3 precipitation. Suspended particles trapped by cyanobacteria increased the surface area for crystal growth to further accelerate precipitation. The contribution of photosynthesis-induced CaCO3 precipitation was low because of several factors, including variable cyanobacteria populations and photosynthetic inhibition of CaCO3 precipitation. The average contributions of photosynthesis-induced CaCO3 precipitation, Ca2+ adsorption and abiotic precipitation in the eight hot springs were 16%, 3% and 81%, respectively, indicating predominance of the abiotic process for travertine deposition. Mineralogical composition of travertines significantly correlated with concentrations of SO42− and Mg2+, much more than with Mg/Ca ratio and water temperature, suggesting their importance for controlling CaCO3 polymorphs in travertines.

The complex problem of inorganic scale formation on heat transfer surfaces is of substantial importance for industrial and domestic systems. Formation of mineral scale, particularly calcium carbonate, has long been a concern in domestic appliances such as boilers, steamers and washing machines. Here, the formation of solid inorganic deposits was studied on solid surfaces and in the bulk solution as a result of evaporation of natural potable water. Scale precipitation rates were evaluated for metallic samples for various bulk temperatures, surface roughness values and as a function of time. The morphology of crystals from both surface and solution was evaluated. The concentration of calcium ions was evaluated using Atomic Absorption Spectrophotometry (AAS), in order to investigate the kinetics of the precipitation reaction. The microstructure and morphology of deposits on the surface were analysed using Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD). The present work has demonstrated that fouling deposition rates increase as the evaporation process proceeds as expected. The nature of the material and the surface roughness both affect surface deposition kinetics. The complex relationship between the saturation ratio (as the bulk solution shows precipitation) and the kinetics of bulk and surface precipitation/deposition is demonstrated. The prevailing crystalline form of calcium carbonate as detected by SEM and XRD is aragonite. However, the polymorphic composition of surface deposition and the bulk precipitate is influenced by temperature.

Single-phase CaxSr1–xCO3 solid solutions with an aragonite structure and x = 0–1 were obtained by precipitation synthesis and characterized with respect to their structural, physical, and thermodyn...

The Bering sea is susceptible to ocean acidification driven by both human activities (anthropogenic CO2) and distinctive natural processes. To assess the situation of ocean acidification, we investigated the spatial variability of aragonite saturation states (ΩAr) in July 2010 during the 4th Chinese National Arctic Research Expedition (CHINARE). The surface waters were all oversaturated with respect to aragonite (ΩAr > 1) due to high biological removal, and ΩAr ranged from 1.43 to 3.17. The relatively low ΩAr values were found in the western Bering Strait and eastern nearshore region of the Bering Sea Shelf, which were associated with the upwelling and riverine input, respectively. In the subsurface, the ΩAr decreased to generally low saturation states and were observed to be strongly undersaturated (ΩAr

Monohydrocalcite (MHC) is hydrated calcium carbonate, which plays an active role in many geological processes, carbonate biomineralization, and can be used for fundamental science (as a paleoenvironmental indicator) and industry (for removal of hazardous anions). Despite a great number of works, the conditions preferable for MHC formation/stabilization and MHC crystal chemical patterns in relation to Mg and H2O are not clarified yet. In the course of current work, we conducted 38 syntheses to obtain information on MHC formation at different Mg/Ca ratios (0–12), pH (~9–12), and temperature (23 and 3 °C). Newly formed carbonate precipitates were studied by means of X-ray powder diffraction, optical, and scanning electron microscopy, energy-dispersive X-ray spectroscopy, Raman, and Fourier-transform infrared (FTIR) spectroscopies. The phase diagram for MHC, calcite, aragonite, and dypingite as a function of pH and Mg concentration in solution at T = 23 °C and Ca/CO3 = 0.5 was obtained. We demonstrated that MHC could be stable in dry conditions for up to two years and that the time of crystallization is important for the transformation of amorphous calcium carbonate to MHC. Our results on synthetic MHC stability show that the widespread idea that MHC is a short-lived intermediate phase is wrong. For the first time, on the basis of a regular changes in the unit-cell parameters the possibility of significant incorporation of magnesium in MHC has been demonstrated. According to FTIR data, it is shown to be accompanied by an increase in the water content, which leads to multidirectional change in a and c MHC parameters.

Based on the crystallographic results, the crystal structure formation mechanism (crystal dynamics) of KCaNd(BO3)2 and BaB2O4 compounds is presented. Close similarity of the first structure with aragonite CaCO3 and of the second with hexagonal carbonates is shown. High pseudo-symmetry is noted, bringing the structures to the maximum symmetry possible for hexagonal crystals.

Calcium carbonate (CaCO3 ), a mineral commonly found in the Earth's crust, is mainly in the forms of calcite and aragonite. Calcite has the most stable type of thermodynamics at room temperature and ambient pressure. It has wide band gap structure and is of great interest for a wide-range technical and industrial applications due to its physical properties and suitability. In this study, a new method based on the long short-term memory (LSTM) model of deep learning is proposed to classify the thermoluminescence properties such as fading, cycle of measurement, heating rate, and dose-response of CaCO3 . Therefore the thermoluminescence properties of calcite was investigated as a suitable band structure and its coherent data were used to classify the features using a deep learning LSTM model. Experiments were carried out on a dataset consisting of four classes. The accuracy, precision, and sensitivity values of the proposed model obtained were 98.34, 97.90, and 98.56%, respectively. The classification process of the results obtained from the designed model showed good performance.

The vermetidae fossils ofPetaloconchus varians, formed by calcium carbonate, associated with their radiocarbon ages, are the most accurate indicators of paleo sea level due to their restricted occupation in the intertidal zone in the rocky shore. However, the recrystallization of minerals can affect these age calculations and, consequently, the interpretation of the data. The aim of this study is to present new indicators of paleo sea-level changes in Southeast Brazil for the last 6000 years contributing to fill the data gap for the late Holocene. The influence of the recrystallization process was successfully resolved using the CarDS protocol, enabling the separation of the original aragonite fraction by density, prior to radiocarbon dating. This avoids the rejuvenation of ages and ensures greater efficiency for data interpretation. Paleo sea-level indicators were able to show a progressive increase in sea level up to the transgressive maximum of 4.15 m in 3700 BP years, followed by a regression to the current zero. This regression seems to have in addition, here we reinforce the reliability of the use of fossil vermetids as indicators of sea-level fluctuations.

Among Bagre genera, there is a high variation in the estimation of age, a concern due to overexploitation risk in fisheries because of age underestimation. Bagre panamensis is an important fishery resource of the Mexican Pacific and the Gulf of California. Its age is known from otoliths, but its accuracy needs to be confirmed, and the periodicity of the otoliths record validated. The external morphology, some microstructure attributes, and age record of B. panamensis' otoliths were described from 371 specimens collected southeast of the Gulf of California. The lapilli otoliths were larger than the sagittae and asterisci otoliths. The lapilli otoliths present aragonite crystals with a prismatic shape, and their growth is radial, from the core to the otolith edge. The lapilli otoliths form an annual growth ring, defined by the slowdown in the growth that occurs during April to July, during the breeding season. The ages of the individuals ranged from 1 to 15 years, and the applied method is considered adequate and accurate for its estimation (otolith cross-sectioning and red-neutral staining).

The crystallographic analysis of three modifications of CaCO3 – rhombohedral calcite ( $$R\bar{3}c$$ ), orthorhombic aragonite (Pmcn), and monoclinic vaterite (C2/c) – reveals different mechanisms of atomic ordering in the structures. An important role in the formation of a specific structure is played by the point symmetry of energetically stable atomic groups (templates) in the precrystallization phase, which depends on the crystallization conditions, impurities, and local heterogeneities. Then the template symmetry forms the structure symmetry by placing heavy atoms and mass centers of stable CO3 atomic groups mainly in special positions with fixed coordinates. The details of this crystal dynamics (the ordering of atomic positions by translational and point symmetries) are shown.

A plagioclase megacryst containing composite crystal-glass inclusions was ejected in a Pliocene basaltic diatreme in the Carpathian back-arc basin (Pannonian Basin). The megacryst grew from phonolitic melt, relics of which are preserved in the crystal-glass inclusions. Most of the pristine melt has undergone substantial compositional resetting by interaction with several batches of a low-viscosity carbonated, P-rich melilitite melt, which infiltrated and largely replaced the original inclusion content. The melilitite melt also caused partial resorption of the host megacryst and crystallisation of new calcic plagioclase forming stringers and palisades. A P-rich calcic carbonatite melt exsolved from the melilitite and later crystallised to aragonite at ~ 800 °C and 1.9 GPa. The phosphate melt fraction exsolved from the carbonatite and solidified as CO32−-rich A-B type apatite. At a very late evolutionary stage, K- and Si-rich fluids caused potassic and silicic alteration of the solidified melilitite glass along cracks and interfaces between calcic carbonate globules and glass at temperatures below 680 °C. The oxygen isotope composition of the plagioclase megacryst (6.2 ‰ V-SMOW; Vienna Standard Mean Ocean Water) and the 87Sr/86Sr isotope ratio of carbonates in the inclusions (0.7034) are consistent with a mantle-derived melt. 87Sr/86Sr isotope ratios (0.7047–0.7051) in interstitial carbonates from associated syenite and carbonatite xenoliths indicate a metasomatised mantle source contaminated with radiogenic crustal material or altered marine carbonate. The O-isotope ratios in the carbonates, 22.7 ± 0.6 ‰ V-SMOW in calcite and 23.6 ± 0.7 ‰ V-SMOW in aragonite, are also consistent with a sedimentary precursor. Contrasting δ13C values in the calcite, -12.7 ± 0.5 ‰ V-PDB (Vienna PeeDee Belemnite), and the aragonite (-4.6 ± 0.5 ‰ V-PDB) indicate low-temperature modification of calcite assisted by $$\delta$$ δ 13C-depleted CO2 and preservation of primary magmatic $$\delta$$ δ 13C values in aragonite. The microstructural and geochemical evidence points towards heterogeneous silicate-carbonate melt fractions generated during the metasomatism and partial melting of a supra-subduction mantle wedge.

The need for the possibility of producing calcium carbonate crystals by the evaporation method within five minutes and the growth of different calcium carbonate polymorphs on chitin whiskers within the same time frame at room temperature necessitated these report. Chitin whiskers (CHWs) were used as insoluble substrates, while poly (acrylic) acid (PAA) is used as soluble additive. The crystals were grown in chitin whiskers, Poly (acrylic) acid and CHW/PAA composites. The volume fractions for aragonite, vaterite, and calcite are 0.10, 0.25, and 0.65, respectively, in the absence of chitin whiskers or Poly (acrylic) acid. Calcite and aragonite volume fractions decrease in favour of vaterite when PAA and or CHWs were added. SEM images in the absence of CHWs and PAA shows rhombohedral calcites that display steady and step like plane appearances with an average edge of between 1.3 and 1.4 μm. In the presence of only CHWs, the SEM images show a mixture of ellipsoidal and spherical shape vaterites. The spherical vaterites have smooth, rough, and some irregular surfaces. Rod-like aragonite polymorphs were seen when only PAA was used as the template. In the presence of both PAA and CHWs, the rhombohedral shape showed roughness with irregular faces. Keywords: Chitin whisker, Calcium carbonate, Calcium, vaterite aragonite, Polymorph, Mole fraction

In this paper, we describe porosity variations in Miocene to Holocene carbonates off the west coast of Australia and assess their compaction trends. The porosity values were measured using discrete samples of Sites U1459–U1464 obtained by the International Ocean Discovery Program Expedition 356. The carbonate deposits have been influenced by a range of textures and diagenetic conditions throughout a nearly continuous sequence of geological ages from the Miocene to Holocene and at core depths from 0 to 1100 m below the seafloor. The collected samples were mostly grainstone, packstone, wackestone and mudstone textures. Dolostones and dolomitic carbonates were described at the Miocene intervals. Compaction trends were estimated exponentially and linearly based on cored sites, carbonate textures and dominant mineralogies (dolomite, calcite/aragonite). At all six sites, porosity distribution and reduction were generally depth-dependent. The porosity converged to about 30% between 750 and 1100 m, which suggests that the carbonates were close to the densest packing by mechanical compaction at a burial depth of ∼750 m. The porosity deviations are associated with textures and dominant mineralogies. Increasing mud content from grainstone to mudstone is a controlling factor for initial porosity and porosity reduction rate. Dolomitisation, dolomitic cementation, aragonite needle-rich mud and non-skeletal grains cause deviations from the depth-dependent compaction trends. Reflux-related cementation generally decreases porosity in Miocene dolomitic intervals. Higher porosity values of the Quaternary wackestone and mudstone at Site U1461 resulted from the presence of aragonite needle-rich mud hosting abundant micropores and from a high sedimentation rate. The occurrence of non-skeletal grains, such as ooids and peloids, as well as occasional meteoric exposure led to porosity inversion, occluding interparticle permeability and the creation of moldic pores.

The Cedars ultramafic block hosts alkaline springs (pH > 11) in which calcium carbonate forms upon uptake of atmospheric CO2 and at times via mixing with surface water. These processes lead to distinct carbonate morphologies with “floes” forming at the atmosphere-water interface, “snow” of fine particles accumulating at the bottom of pools and terraced constructions of travertine. Floe material is mainly composed of aragonite needles despite CaCO3 precipitation occurring in waters with low Mg/Ca ( The calcium carbonates exhibit an extreme range and approximately 1:1 covariation in δ13C (−9 to −28‰ VPDB) and δ18O (0 to −20‰ VPDB) that is characteristic of travertine formed in high pH waters. The large isotopic fractionations have previously been attributed to kinetic isotope effects accompanying CO2 hydroxylation but the controls on the δ13C-δ18O endmembers and slope have not been fully resolved, limiting the use of travertine as a paleoenvironmental archive. The limited areal extent of the springs (∼0.5 km2) and the limited range of water sources and temperatures, combined with our sampling strategy, allow us to place tight constraints on the processes involved in generating the systematic C and O isotope variations. We develop an isotopic reaction–diffusion model and an isotopic box model for a CO2-fed solution that tracks the isotopic composition of each dissolved inorganic carbon (DIC) species and CaCO3. The box model includes four sources or sinks of DIC (atmospheric CO2, high pH spring water, fresh creek water, and CaCO3 precipitation). Model parameters are informed by new floe Δ44Ca data (−0.75 ± 0.07‰), direct mineral growth rate measurements (4.8 to 8 × 10−7 mol/m2/s) and by previously published elemental and isotopic data of local water and DIC sources. Model results suggest two processes control the extremes of the array: (1) the isotopically light end member is controlled by the isotopic composition of atmospheric CO2 and the kinetic isotope fractionation factor (KFF (‰) = (α − 1) × 1000) accompanying CO2 hydroxylation, estimated here to be −17.1 ± 0.8‰ (vs. CO2(aq)) for carbon and −7.1 ± 1.1‰ (vs. ‘CO2(aq) + H2O’) for oxygen at 17.4 ± 1.0 °C. Combining our results with revised CO2 hydroxylation KFF values based on previous work suggests consistent KFF values of −17.0 ± 0.3‰ (vs. CO2(aq)) for carbon and −6.8 ± 0.8‰ for oxygen (vs. ‘CO2(aq) + H2O’) over the 17–28 °C temperature range. (2) The isotopically heavy endmember of calcium carbonates at The Cedars reflects the composition of isotopically equilibrated DIC from creek or surface water (mostly HC O 3 - , pH = 7.8–8.7) that occasionally mixes with the high-pH spring water. The bulk carbonate δ13C and δ18O values of modern and ancient travertines therefore reflect the proportion of calcium carbonate formed by processes (1) and (2), with process (2) dominating the carbonate precipitation budget at The Cedars. These results show that recent advances in understanding kinetic isotope effects allow us to model complicated but common natural processes, and suggest ancient travertine may be used to retrieve past meteoric water δ18O and atmospheric δ13C values. There is evidence that older travertine at The Cedars recorded atmospheric δ13C that predates large-scale combustion of fossil fuels.

Study of the preferred orientation of biological materials (bones, shells, etc.) is the use of crystallographic methods in biophysics to search for new possibilities in materials science. Much attention is paid to the texture of the bivalve mollusk shells. However, for a qualitative systematic investigation of the preferred crystallographic orientation of these shells, it is necessary to examine many representatives from different parts of the world. X-ray diffraction was used to study the preferential crystal orientation of adult shell of the species Sinanodonta woodiana collected from Czech freshwater streams. The texture of artificially grown young shells was also measured. The pole figure measurements of the Aragonite phase (planes (111), (102), (200), (121), (022) and (122)) were performed using a SmartLab Rigaku high-resolution X-ray diffractometer with a rotating Cu anode (Institute of Physic, Prague, Czech Republic).

This paper reports a laboratory-based case study for the characterization of deposits from a crude cooler and reboilers in a Saudi Aramco refinery by microbiologically influenced corrosion (MIC) using microbial, metallurgic, and special analyses and correlates the Rietveld quantitative phase analysis of high-resolution X-ray powder diffraction (XRD) data of scale deposits with microbe compositions. Therefore, rapid in-field microbiological assays could be carried out to assess the potential of MIC. Based on the results, it can be highlighted that the MIC investigation showed that total bacteria and sulfate-reducing bacteria (SRB) were detected in all sampling locations. Methanogens, acid-producing bacteria, and sulfate-reducing archaea were not detected in all samples. Iron-oxidizing bacteria (IOB) were detected in the solid samples from reboilers C and D. Low loads of general bacteria and low levels of microbes with MIC potential were detected in both C and D samples. The trace amount of corrosion products in one sample and the low level of MIC microbes cannot justify the contribution of MIC microbes in the formation of accumulated solids in the system. The findings recommend conducting frequent sampling and analysis including water, oil, and solid from upstream locations to have more decisive evidence of the likelihood of the scale formation and possible contribution of MIC in the formation of deposits in the plant. Subsequently, quantitative phase analysis of XRD data of scale deposits by the Rietveld method revealed that the major phase is calcium sulfate in the form of anhydrate and the minor phases are calcium carbonate in the form of calcite and aragonite, silicon oxide in the form of quartz, and iron oxide corrosion product in the form of magnetite. The results are supported by high-resolution wavelength-dispersive X-ray fluorescence (WDXRF) results. These accurate and reproducible X-ray crystallography findings obtained from Rietveld quantitative phase analysis can guide the field engineers at the refineries and gas plants to overcome the problems of the affected equipment by drawing up the right procedures and taking preventive actions to stop the generation of these particular deposits.

The purpose of this study is to examine hydrochemical changes of saline groundwater and precipitation of mineral phases during evaporative graduation processes. Therefore, concentrated brines and mineral precipitates were sampled at four graduation towers with differing evaporation approaches. Solid phase compositions were qualitatively and quantitatively analysed. Hydrochemistry changes of dissolved ion concentrations during successive evaporation was assessed by comparing natural with concentrated brines. PHREEQC was used to simulate sequence and quantity of mineral precipitates. Finally, a prognosis for expected precipitations of a newly built graduation tower was made using PHREEQC modelling. The identified mineral phases included calcite, aragonite, gypsum and halite in varying proportions. Concentrations of all investigated ions (except bicarbonate) increase, eventually leading to supersaturation and sequential precipitation of evaporite minerals. Modelled saturation indices show that calcite is the first and halite is one of the last precipitating phases at all sites. Further calculated precipitates include the carbonates dolomite, siderite and strontianite; manganese oxide and hematite; and the sulphates baryte, celestine and gypsum which precipitate depending on local hydrogeochemistry and graduation conditions. Calculated precipitation quantities reach a maximum of 48.6 g/L of applied natural brine at an evaporation grade of 90%. After 25 years, the total expected mass of precipitates at the new graduation tower is about 34.4 t for a graduation process up to a salt content of 19%, and about 356 t for a permanent evaporation grade of 90%. • Except for bicarbonate, concentrations of all ions increase to different degrees. • Mineral precipitations are composed of calcite, aragonite, gypsum and halite. • Modelled precipitation sequence: carbonates, sulphates, chlorides. • Modelled precipitation amounts: max. 48.6 g/L for natural brine at 90% evaporation. • 25 y precipitation forecast for new graduation tower: max. 356 t at 90% evaporation.

Recent studies using the CO2 carbonate clumped isotope (13C-18O-16O, i.e., Δ47) paleothermometer and bulk isotopes (δ13C, δ18O) have brought new insights into the prevailing conditions during carbonate formation around marine methane seeps. These studies mostly revealed δ18O or paired δ18O and Δ47 disequilibria between precipitating minerals, water and DIC species. Here, we have sampled bivalves and cements from two modern, slow-release methane seeps located in the St. Lawrence Estuary. The bivalve shells have marine isotopic signals, whereas the cements show wide Δ47 (up to +0.05‰) and minor δ18O (+0.8‰) positive offsets relative to marine equilibrium, with a narrow δ13C range (−33.5 to −31.1‰). The observed isotopic trends show that, unlike in previous studies, the aragonite shells precipitated at full isotopic equilibrium, whilst the cements suggest differential disequilibrium precipitation. We propose that the suite of results were generated by distinct Δ47 and δ18O pathways, as supported by DIC-water isotopic exchange numerical experiments. The observed trends typify slow rates of methane oxidation and carbonate precipitation from residual gas with high-δ18O and low-Δ47 values after methane-derived CO2 diffusion. Overall, we suggest that the shells represent potential archives of seep conditions, and that the seep cements define a new Δ47 and δ18O domain widening the known spectrum of marine conditions producing natural carbonates. Our results, compiled with literature data, help refine the basis for interpreting carbonate precipitation mechanisms in ancient seeps or other geological settings.

The abiotic synthesis of histidine under experimental prebiotic conditions has proven to be chemically promising and plausible. Within this context, the present results suggest that histidine amino acid may function as a simple prebiotic catalyst able to enhance amino acid polymerization. This work describes an experimental and computational approach to the self-assembly and stabilization of DL-histidine on mineral surfaces using antigorite ((Mg, Fe)3Si2O5(OH)4), pyrite (FeS2), and aragonite (CaCO3) as representative minerals of prebiotic scenarios, such as meteorites, and subaerial and submarine hydrothermal systems. Experimental results were obtained through polarized-light microscopy, IR spectroscopy (ATR-FTIR), and differential scanning calorimetry (DSC). Molecular dynamics was performed through computational simulations with the MM + method in HyperChem software. IR spectra suggest the presence of peptide bonds in the antigorite-histidine and aragonite-histidine assemblages with the presence of amide I and amide II vibration bands. The FTIR second derivative inspection supports this observation. Moreover, DSC data shows histidine stabilization in the presence of antigorite and aragonite by changes in histidine thermodynamic properties, particularly an increase in histidine decomposition temperature (272oC in antigorite and 275oC in aragonite). Results from molecular dynamics are consistent with DSC data, suggesting an antigorite-histidine closer interaction with decreased molecular distances (cca. 5.5 A) between the amino acid and the crystal surface. On the whole, the experimental and computational outcomes support the role of mineral surfaces in prebiotic chemical evolution as enhancers of organic stability.

Bu çalışmada Özdere-Cumhuriyet mahallesinde yüzeyleyen termal su örneğinin hidrojeokimyasal özellikleri ile etkileşimde olduğu deniz suyu ile olan ilişkisi incelenmeye çalışılmıştır. Çalışma alanı Menderes ilçesi’nin onaylı tek turizm bölgesi olan ve İzmir iline 45km mesafedeki Özdere-Cumhuriyet mahallesinde yer almaktadır. Menderes metamorfikleri içerisindeki mermer mercekleri ile alüvyon bölgedeki sular için rezervuar kayaç özelliğindedir. Yeraltına süzülen soğuk sular, fay ve çatlaklar boyunca hareket ederek ısınmakta, fayların kesim noktası olarak düşünülen bir zon üzerinde yüzeylemektedir. Bu esnada gerek su kayaç etkileşimi gerekse deniz suyu karışımına bağlı olarak güncel kompozisyonlarını kazanmaktadır. İncelenen termal kaynak ve deniz suyu örnekleri Na-Cl, soğuk su örnekleri ise Ca-HCO3 bileşimlidir. Su örneklerinin kimyasal kompozisyonunu oluşturan ana mekanizmalar su-kayaç etkileşimi ve buharlaşma/kristalizasyon olarak belirlenmiştir. Yapılan değerlendirmeler sonucunda; termal su örneğinin %28 tatlı su ve %72 deniz suyu bileşiminden oluştuğu, rezervuar sıcaklığının 78-86°C arasında olabileceği ve bu suyun kalsit, aragonit, dolomit ile kuvars ve kalsedon gibi mineralleri çökeltici özellikte olduğu tespit edilmiştir.

We present a new natural carbon dioxide (CO 2 ) system located off the southern coast of the island of La Palma (Canary Islands, Spain). Like CO 2 seeps, these CO 2 submarine groundwater discharges (SGDs) can be used as an analogue to study the effects of ocean acidification (OA) on the marine realm. With this aim, we present the chemical characterization of the area, describing the carbon system dynamics, by measuring pH, AT and CT and calculating Ω aragonite and calcite. Our explorations of the area have found several emission points with similar chemical features. Here, the CT varies from 2120.10 to 10 784.84 µ mol kg −1 , AT from 2415.20 to 10 817.12 µ mol kg −1 , pH from 7.12 to 8.07, Ω aragonite from 0.71 to 4.15 and Ω calcite from 1.09 to 6.49 units. Also, the CO 2 emission flux varies between 2.8 and 28 kg CO 2 d −1 , becoming a significant source of carbon. These CO 2 emissions, which are of volcanic origin, acidify the brackish groundwater that is discharged to the coast and alter the local seawater chemistry. Although this kind of acidified system is not a perfect image of future oceans, this area of La Palma is an exceptional spot to perform studies aimed at understanding the effect of different levels of OA on the functioning of marine ecosystems. These studies can then be used to comprehend how life has persisted through past eras, with higher atmospheric CO 2 , or to predict the consequences of present fossil fuel usage on the marine ecosystem of the future oceans.

The late Quaternary shallow-water carbonates have been altered by a variety of diagenetic processes, and further influenced by high-amplitude global and regional sea level changes. This study utilizes a new borehole drilled on the Yongxing Island, Xisha Islands to investigate meteoric diagenetic alteration in the late Quaternary shallow-water carbonates. Petrographic, mineralogical, stable isotopic and elemental data provide new insights into the meteoric diagenetic processes of the reef limestone. The results show the variation in the distribution of aragonite, high-Mg calcite (HMC) and low-Mg calcite (LMC) divides the shallow-water carbonates in Core SSZK1 into three intervals, which are Unit I (31.20–55.92 m, LMC), Unit II (18.39–31.20 m, aragonite and LMC) and Unit III (upper 18.39 m of core, aragonite, LMC and HMC). Various degrees of meteoric diagenesis exist in the identified three units. The lowermost Unit I has suffered almost complete freshwater diagenesis, whereas the overlying Units II and III have undergone incompletely meteoric diagenesis. The amount of time that limestone has been in the freshwater diagenetic environment has the largest impact on the degree of meteoric diagenesis. Approximately four intact facies/water depth cycles are recognized. The cumulative depletion of elements such as strontium (Sr), sodium (Na) and sulphur (S) caused by duplicated meteoric diagenesis in the older reef sequences are distinguished from the younger reef sequences. This study provides a new record of meteoric diagenesis, which is well reflected by whole-rock mineralogy and geochemistry.

We analyze 214 freshly laid eggs belonging to 16 species across three orders of Class Reptilia. Using mechanical compression tests, we measure each egg’s absolute stiffness (K, unit: N m−1) and relative stiffness (C number). The effective Young’s modulus, E, was obtained by combining experimental and numerical methods. The mineral (CaCO3) content was measured by acid–base titration, the microstructures by scanning electron microscopy (SEM), and the crystallography by electron backscatter diffraction (EBSD). We find that the C number of reptilian eggs is, on average, higher than that of bird eggs, indicating that reptilian eggs are stiffer with respect to the egg mass than birds. However, Young’s moduli of the reptilian eggshells (32.85 ± 3.48 GPa) are similar to those of avian eggshells (32.07 ± 5.95 GPa), even though those eggshells have different crystal forms, microstructures, and crystallography. Titration measurement shows that the reptilian eggshells are highly mineralized (>89% for nine Testudines species and 96% for Caiman crocodilus). Comparing the species with aragonite and calcite crystals, we find that calcite shells, including those of the Kwangsi gecko (inner part) and spectacled caiman (outer part), generally have larger grains than the aragonite ones. However, the grain size is not correlated to the effective Young’s modulus. Also, as measured by the C number, the aragonite shells are, on average, stiffer than the calcite ones (except for the Kwangsi gecko), primarily due to their thicker shells.

Ex situ aqueous mineral carbonation of ultramafic mining waste is an evolving technology for the CO2 sequestration from small- to medium-scale emitters. The mineral ores or mine wastes of associated ultramafic mineralogy are a suitable feedstock for mineral carbonation. The aqueous mineral carbonation at ambient temperature is motivating and attractive from an energy-saving perspective. This study has investigated the CO2 sequestration potential of a locally available ultramafic material generated from a nickel ore mine with a futuristic scope of integrating the method into an ongoing mineral extraction and/or tailing management operation. The mineral characterization and experimental results indicate that the tested material has CO2 sequestration potential and underwent carbonation at ambient temperature. The carbonate conversion efficiencies obtained for Ca and Mg from the dissolved ionic forms at optimum conditions are 60% and 25%, respectively. The material was able to sequestrate about 0.12 gCO2 per g solid at this efficiency. Aragonite and hydromagnesite are the major products that evolved out from the aqueous carbonation. Based on the mineral carbonation results, the novel concept of integrating the evolved method to existing mineral extraction and/or tailings management operation is discussed.

Lower Triassic limestones contain giant ooids (>2 mm) along with other precipitated carbonate textures more typical of Precambrian strata. These features appear to have resulted from changes in seawater chemistry associated with the end-Permian mass extinction, but quantifying the carbonate chemistry of Early Triassic seawater has remained challenging. To constrain seawater carbonate saturation state, dissolved inorganic carbon, alkalinity, and pH, we applied a physicochemical model of ooid formation constrained by new size data on Lower Triassic ooids from south China, finding that the Triassic giant ooids require a higher carbonate saturation state than typifies modern sites of ooid formation. Model calculations indicate that Early Triassic oceans were at least seven times supersaturated with respect to aragonite and calcite. When combined with independent constraints on atmospheric pCO2 and oceanic [Ca2+], these findings require that Early Triassic oceans had more than twice the modern levels of dissolved inorganic carbon and alkalinity and a pH near 7.6. Such conditions may have played a role in inhibiting the recovery of skeletal animals and algae during Early Triassic time.

We provide up-to-date morphological and compositional data on otoliths of the osteoglossomorph Goldeye (Hiodon alosoides). Using computed tomography (CT) X-ray, we documented the location of each of the three pairs of otoliths (lapilli, sagittae, and asterisci) in relation to the swim bladder, which extended forward in close proximity to the sagittae and asterisci. The lappili were the largest otoliths in terms of surface area and volume, but the sagittae were highly modified, appearing spiral in shape when viewed dorsally, with a surface area to volume ratio more than double that of the lapilli. Using scanning electron microscopy, the surface of each otolith was viewable in great detail, and small otoconia (~10.5 μm diameter) were observed on each, but were most numerous on the sagittae. On scanning electron micrographs, the sagittae appeared to be bi-lobed, with asymmetrical lobes each oriented in the same general direction. Using neutron and X-ray diffraction methods, we found three polymorphs of calcium carbonate crystals (aragonite, vaterite, and calcite), sometimes all within the same otolith. However, in general, lapilli and sagittae were composed predominately of aragonite whereas asterisci were composed chiefly of vaterite. With these results, we provide information on a unique species, whose inclusion in future studies would benefit our understanding of fish hearing, fish evolution, and fisheries ecology.

Stable δ13C isotope analysis at hot and cold springs suggests that rapid degassing overprints carbon isotopic biosignatures even when microbial activity produces biogenic textures in the minerals. Mineral precipitation and potential biosignature preservation are evaluated at a cold spring system in Ten Mile Graben, Utah, USA, with scanning electron microscopy, X-ray diffraction, and stable carbon isotopes. Putative biogenic mineral habits such as aragonite microspheres and botryoids, and biologic materials (EPS and diatom tests) are abundant in modern mats, but the δ13C values are between +2‰ and +7.8‰, consistent with rapid CO2 degassing reported by other researchers. Multiple factors, however, influence isotopic signatures of mineral precipitates in this spring system, including rapid degassing, preferential microbial uptake of light carbon isotopes via multiple carboxylation pathways, hydrocarbon-charged fluid, and other inherited isotopic signatures in the fluid, particularly from dissolution of older limestones; therefore, it is not likely that this narrow range of isotopic ratios definitively shows an abiotic signature. A fossil vent preserves biogenic mineral habits, but not microbial body fossils. This study highlights the need for novel biosignature detection methods-and an understanding of what an abiotic signature definitively is-as we prepare for sample caching of carbonate rocks by the Mars2020 mission and future sample return.

Characterization of material on cockle shell has been wiped out the shells hills of the Bendahara district of Aceh Tamiang district, with the aim of knowing the basic content and diffraction patterns of the cockle shell to plain CaCO3 aragonite. The research method begins with sampling the cockle shell from the Kerang hill. Firstly, preparation cockle shell. Then, characterized by X-Ray Fluorescence (XRF) examining to work out the basic content within the cockle shell, then doing Scanning M icroscopy Energy Dispersive X-Ray (SEM-EDX), and X-ray diffraction ( XRD) testing. The characterization leads to XRF testing showed that the content of the constituent elements of the CaCO3 compound was dominated by CaO of 98.93% at station I and at station II, CaO was obtained the maximum amount as 98.73%. In SEM analysis, the cockle shell have a rod-like morphological structure within the sort of aragonite crystals. The results of EDX at station I, obtained CaO elements is 58.18% and at station II CaO is 36.76%. The results of XRD analysis, the cockle shell have an aragonite phase with an orthorombic crystal structure. the very best phase that appears at 2θ at station I is 26,220, and station II is 26,280.

The shells of calcitic arthropod Amphibalanus improvisus; aragonitic bivalves Cerastoderma glaucum, Limecola balthica, and Mya arenaria; and bimineralic bivalve Mytilus trossulus were collected in the brackish waters of the southern Baltic Sea in order to study patterns of bulk elemental concentration (Ca, Na, Sr, Mg, Ba, Mn, Cu, Pb, V, Y, U and Cd) in shells composed of different crystal lattices (calcite and aragonite). The factors controlling the elemental composition of shells are discussed in the context of crystal lattice properties, size classes of organisms and potential environmental differences between locations. Clams that precipitate fully aragonitic shells have a clear predominance of Sr over Mg in shells, contrary to predominant accumulation of Mg over Sr in calcitic shells of barnacles. However, the barnacle calcite shell contains higher Sr concentration than bivalve aragonite. The elemental variability between size-grouped shells is different for each studied species, and the elemental concentrations tend to be lower in the large size classes compared to the smaller size classes. Biological differences between and within species, such as growth rate, feeding strategy (including feeding rate and assimilation efficiency or composition) and contribution of organic material, seem to be important factors determining the elemental accumulation in shells. Because specimens used in this study were obtained from different sampling sites within the gulf, the impact of location-specific environmental factors, such as sediment type, cannot be excluded.

The Salish Sea, spanning Washington State and British Columbia, receives relatively low pH water from upwelling in the northeast Pacific Ocean and the acidity of bottom water increases within the sea, particularly in winter. In order to better understand the processes that lead to bottom water acidification in this region, I quantified the sources of dissolved inorganic carbon (DIC) and alkalinity to bottom water in Bellingham Bay, a small embayment that is nevertheless representative of the broader Salish Sea. Corrosive bottom water with a pH of 7.5 and an aragonite saturation state of 0.51 was observed in deep water the northern portion of the bay. Water column respiration contributed 6.8 mmol DIC m−3 d−1 to bottom water while sediments added both DIC (13.6 mmol m−2 d−1) and alkalinity (9 mmol m−2 d−1). A two-layer box model assessed the relative importance of sources of corrosive water to the bay and calculated how bottom water pH and aragonite saturation state vary during spring. The 30-day model run calculated increases in bottom water DIC and alkalinity but decreases in bottom water pH and aragonite saturation state along with oscillations of these parameters with a period of approximately 6 days. A sensitivity analysis of the model demonstrated that water column respiration was the primary driver of corrosive bottom-water production. Sediment respiration contributed less to the production of corrosive water but was a source of alkalinity. The accumulation of corrosive bottom water in Bellingham Bay was also a function of mean circulation; the slowing of bottom water flow led to longer bottom-water residence time and an increase in bottom water corrosivity.

The hydrozoan Millepora dichotoma (MD) is a typical Red Sea species containing a porous skeleton in the form of aragonite crystalline calcium carbonate. Due to environmental considerations, the artificial production of coralline species under controlled conditions is pertinent and underway. Artificially grown MD was used as a raw material for the production of calcium phosphate, mainly hydroxyapatite bioceramics, to be used in the drug delivery systems as a drug carrier or in the tissue engineering such as bone graft. DTA-TGA, XRD, FT-IR, Raman, and SEM analysis were carried out to analyze both unconverted and converted artificial corals. Hydrothermally converted coral fine powders were loaded with gentamicin (Gm) antibiotic, and the drug-loaded particles were analyzed by SEM. Unconverted coral was mainly aragonite, while hydrothermally treated coral was completely converted to hydroxyapatite. Hydrothermally treated coral was showing agglomerated nodules up to 1-μm size consisting of nanocrystalline hydroxyapatite platelets in the size range of less than 100 nm. The general macropore size of the coral was found to be appropriate for osteoid growth, which is 100 to 600 μm range. These artificially grown corals can be easily produced and used for bone growth and repair and other biomedical applications.

We present the results of studying the Holocene sediments of Bolshie Toroki Lake, a shallow brackish lake with carbonate sedimentation and high bioproductivity, located in the eastern part of Baraba lowland (southwestern Siberia). The mineral component of bottom sediments was studied by such methods as X-ray diffraction (XRD) analysis, IR spectroscopy, laser granulometry, elemental analysis, and others. By the mathematical modeling of complex XRD patterns, Mg-calcites with different Mg contents and aragonite have been established in the assemblage of carbonate minerals. Their structural and crystallochemical features and quantitative ratios were determined. The obtained high-resolution carbonate record was compared in the dated section with the distribution of the ash content, which is determined by the bioproductivity of the basin, and with a number of geochemical indicators of climate changes. The use of such a complex approach allowed us for the first time to recognize four stages in the evolution of Bolshie Toroki Lake; these stages were caused by cycles of drying/wetting of the regional climate and fluctuations of the lake level in the second half of the Holocene. Stage I (middle of the Atlantic) corresponded to the formation of the lake; stage II (second half of the Atlantic) was characterized by shallowing of the lake in a dry and warm climate; stage III (most of the Subboreal), shallow basin in a dry and cool climate; and stage IV (from the end of the Subboreal until the present) was marked by an increase in the water level of the lake and climate humidization.