Calcite

Titanium dioxide (TiO2) due to its high refractive index, is widely used in paint industry as a white pigment. In order to reduce this high cost of TiO2, a part of TiO2 is generally substituted by some other industrial mineral fillers such as calcite and calcined kaolin; however, this substitution affects the quality of paints in terms of stability, coverage (opacity), brightness (gloss), scrub resistance (film toughness), etc. In the present paper, precipitated calcium carbonate (PCC) was substituted for TiO2 in paint mixture at three different pigment volume concentrations (PVC). It was observed that substitution of TiO2 by PCC depends on PVC value at which there is an optimum PCC amount. The quality of paints produced by PCC along with its rheological properties was evaluated based on standard features in both wet and dry paints such as viscosity, density, opacity and gloss values. Addition of PCC increases the opacity to a certain point. Similarly, scrub resistance and viscosity increases with the addition of PCC at all PVCs, however, viscosity is not as much critical for the paint production. On the other hand, there is no any systematic effect of PCC on gloss value of the paint. This study overall demonstrates that PCC can be successfully used to substitute TiO2 only with a careful adjustment of PVC and other extenders used in the paint formulation.

Mollusk shells excavated from archeological sites have been used to reconstruct paleoenvironment, human foraging , and migratory patterns. To retrieve information on past environment or human behavior, chemical signatures such as oxygen stable isotopes (δ 18 O shell) are analyzed. Shell archeological remains usually represent food waste. Thermal treatments such as boiling and roasting may influence shell structure and biochemical composition. However, little is known about the relationship between changes at macro-, microstructural and chemical levels. This work is a calibration study on modern Phorcus (Osilinus) turbinatus shells. A simulation of two different cooking methods (boiling and roasting) was carried out at four temperatures (100 °C, 300 °C, 500 °C and 700 °C) for two durations (20 min and 60 min). The structure and biochemistry of shells boiled at 100 °C did not significantly change. However, treatments at higher temperatures strongly affected both the structure and the biochemistry of the shells. At 300 °C the external coloration, as well as nacre iridescence, were altered. Raman spectroscopy revealed that, at this temperature, the aragonite-calcite polymorphic transformation starts. Scanning electron microscope (SEM) analysis showed drastic changes in the microstructural organization also beginning at 300 °C. Furthermore, the isotopic δ 18 O shell values were significantly affected. Increasing cooking temperatures resulted in an enhancement of the above-mentioned alterations. These results provide a set of temperature-related morphological, structural and biochemical characteristics for investigating the thermal behavior of biocarbonates and for estimating different cooking treatments in archeological record.

Ultrasonically accomplished precipitation of calcium carbonate was demonstrated as a novel beneficial method for the formation of porous submicron vaterite particles with low dispersity, high mass yield, and the ''scaling up " possibility. The effect of sonication on the size and crystallographic phase of formed particles was investigated by comparing this method with a magnetic stirring and non-stirring interfu-sion. By virtue of their porosity, vaterite particles allow the different substance incorporation. The loading properties of synthesized particles were demonstrated for high molecular weight substance (labeled protein), as well as for low molecular one (fluorescent dye). Such features open up perspectives of drug encapsulation and delivery for the vaterite submicron carriers.

— In this study, the effects of liquid additives such as water, triethanolamine (TEA) and ethylene glycol (EG) on the dry fine grinding of calcite were investigated by using a laboratory scale vertical stirred mill. The experiments were carried out by a batch operation, and the change in average particle size (D 50) and specific surface area (SSA) (m 2 /g) and colour properties (L*, a*, b*, ∆E, WI) of product. The results show that the chemical additives and water promotes the fine grinding of calcite and that the maximum specific surface area of calcite (2.97 m 2 /g) obtained with EG additives 0.5%. The average particle size at this point was 3.16 µm. The results also show that the lightness (L) values of the ground calcite products slightly increased from 97.62 to 98.53 with grinding aids (TEA) increased from 0% to 0.5%. The whiteness index (WI) value of the ground calcite products slightly increased from 97.41 to 98.25 with grinding aids (TEA).

The Pre-Pottery Neolithic B (PPNB) is the first period in human cultural evolution that is characterized by the extensive production of lime plaster for architectural, decorative and ritual purposes. The production of large quantities of lime plaster requires the operation of a lime kiln, a structure where limestone cobbles are heated to high temperatures (> 600 °C) to obtain quicklime, which is then mixed with water to form a moldable lime putty. However, little is known about lime kilns and plaster production processes during the PPNB. This may be because the technology used at that time was simple and left few traces that are unique to lime plaster production. These include combustion features rich in lime plaster and heat-altered sediments, which are difficult to identify through only a visual inspection of the archaeological context. Here we report the study of a small sinkhole at the Nesher-Ramla quarry in Israel, which yielded Early PPNB artifacts. Using infrared spectrometry and micromorphology of sediments, we identified in-situ deposits of heat-altered sediments rich in fragments of burnt limestone, lime plaster, and wood ash in the form of charcoal, phytoliths and siliceous aggregates, which are features consistent with the operation of a lime kiln. Charred botanical remains were characterized and used for radiocarbon dating, which determined the age of the site at 10,400 cal BP. We therefore conclude, based on the examination of the microscopic archaeological record, that this sinkhole was used as a lime kiln during the Early PPNB.

This paper presents a new model of fault development in carbonate rocks involving a crack-seal-slip sequence. The structures of sheared calcite veins from the Les Matelles outcrop, Languedoc (S. France), and the observations used to construct this new model which integrates aspects of `crack-seal' evolution of calcite-®lled veins with concepts of fault valve behaviour are described. In our model, hydraulic mode I reopening of an oblique pre-existing vein in an overall strike-slip stress regime is accompanied by precipitation of calcite, but signi®cant fault slip cannot occur initially despite this obliquity because the ends of the pre-existing structure limit further reopening propagation beyond the tips. The rate of aligned calcite precipitation keeps pace with the rate of dilation of the structure, so that calcite cement essentially seals the system. Stress concentrations at the tips are allowed to rise with reopening until failure of the tip zone results in branch crack formation, triggering both slip along the vein and hydraulic pressure drop. This is followed by sealing within the branch cracks. Such a crack-seal-slip cycle may be repeated several times, as evidenced by fault-perpendicular calcite vein growth interlayered with calc-mylonite lamellae within these structures. Later cycles will become less pronounced because strength recovery of the sealed branch cracks does not regain the initial strength of the intact rock. This model could apply at various scales, and could be a mechanism for triggering
earthquakes.

U-series dating is a precise and accurate geochronological tool which is widely applied to date secondary CaCO 3 formation, for example in speleothem based palaeoclimate research. It can also be employed to provide chronological constraints for archaeological sites which have a stratigraphic relationship with speleothem formations. We present in detail our methods to conduct precise and accurate U-Th dating of calcite crusts that formed on top of cave paintings. Our protocols allow the application of U-series measurements on small, thin calcite crusts covering cave art, which can be found in many sites, while taking care not to harm the art underneath. The method provides minimum ages for the covered art and, where possible, also maximum ages by dating the flowstone layer the art is painted on. We present dating results for crusts from two locality types in Spain, a typical cave environment (La Pasiega) and a more open, rock shelter type cave (Fuente del Trucho).

In nature, calcium carbonate (CaCO3) in the form of calcite and aragonite nucleates through different pathways including geogenic and biogenic processes. It may also occur as pyrogenic lime plaster and laboratory-precipitated crystals. All of these formation processes are conducive to different degrees of local structural order in CaCO3 crystals, with the pyrogenic and precipitated forms being the least ordered. These variations affect the manner in which crystals interact with electromagnetic radiation, and thus formation processes may be tracked using methods such as X-ray diffraction and infrared spectroscopy. Here we show that defects in the crystal structure of CaCO3 may be detected by looking at the luminescence of crystals. Using cathodoluminescence by scanning electron microscopy (SEM-CL) and laser-induced fluorescence (LIF), it is possible to discern different polymorphs and their mechanism of formation. We were thus able to determine that pyrogenic calcite and aragonite exhibit blue luminescence due to the incorporation of distortions in the crystal lattice caused by heat and rapid precipitation, in agreement with infrared spectroscopy assessments of local structural order. These results provide the first detailed reference database of SEM-CL and LIF spectra of CaCO3 standards, and find application in the characterization of optical, archaeological and construction materials.

ÖZET 117M659 No'lu TÜBİTAK projesi kapsamında yapılan "Kalsit Morfolojisinin Topaklanma ve Flotasyon Davranışı Üzerindeki Etkisi" isimli bu tez çalışmasında endüstriyel bir mineral olan kalsitin (CaCO3) morfolojik özelliklerinin (şekil faktörü ve pürüzlülük) yanı sıra farklı konsantrasyonlarda kullanılan reaktifin flotasyon ve topaklanma verimlerine etkisi incelenmiştir. Deneysel çalışmalar için yapılan hazırlık doğrultusunda numune çeneli, konili ve merdaneli kırıcıyı içeren 3 kademeli bir kırma prosesinden geçirilip sınıflandırılarak,-2+1 mm boyut grubunda kalsit numunesi elde edilmiştir. Kırma işlemleri sonrasında-2+1 mm boyut grubundaki malzeme bilyalı değirmene beslenmiş ve burada seramik bilyalarla öğütme işlemine tabi tutulmuştur. Öğütme işlemleri sonrası boyut kontrolü yapmak amacıyla numune kuru ve yaş olarak elenmiştir. Farklı sürelerle öğütme işlemine tabi tutulan numune şekil faktörü parametresini belirlemek amacıyla görüntü analizinde işlem yapılmış ve daha sonra SiC ile belirli sürelerle pürüzlendirilmiştir. Farklı şekil faktörü ve pürüzlülük değerlerine sahip kalsit taneleri, tane-tane ve tane-kabarcık arasındaki etkileşimleri açıklamak amacıyla topaklanma ve flotasyon deneylerinde kullanılmıştır. Morfolojik özellikleri belirlenen kalsit taneleri, anyonik bir kollektör olan Sodyum Oleat ile kondüsyonlanmış ve zeta potansiyel, mikro flotasyon ve topaklanma deneylerine tabi tutulmuştur. Aynı işlemler pürüzlendirmeye uğramış taneler için de gerçekleştirilmiştir. Yapılan deneyler sonucunda yuvarlaklık değeri yüksek tanelerin daha düşük flotasyon verimleri verdiği görülmüştür. Ayrıca türbidite deneylerinde de aynı durum gözlenmiş yuvarlaklığı düşük tanelerin daha hızlı şartlandırma davranışı gösterdiği izlenmiştir. ABSTRACT In this thesis titled "Effect of Calcite Morphology on Aggregation and Flotation Behavior" conducted within the scope of TUBITAK project no. 117M659, in addition to the morphological properties (shape factor and roughness) of calcite (CaCO3), which is an industrial mineral, the effect of reagent in different concentrations on flotation and aggregation efficiencies was examined. During the preparation for experimental studies, calcite sample in-2+1 mm size group was passed a 3-stage crushing process involving jaw, cone and roller crusher. After crushing processes, the material in the size group of-2+1 mm was fed to the ball mill and grinded with ceramic balls. The sample was screened dry and wet for size control after grinding operations. The sample, which is grinded for different periods, was sent to image analysis to obtain the shape factor parameter and then roughed up with SiC for certain conditions. Calcite grains with different shape factors and roughness have been used in aggregation and flotation experiments to explain the interactions between bubble-particle and particle-particle interactions. Calcite grains with morphological properties were conditioned with anionic collector Na-Oleate and experienced to zeta potential, micro flotation and aggregation experiments. The same experiments were performed for roughed grains. As a result of the experiments, it was observed that grains with high roundness yielded lower flotation

Construction microbial biotechnology is a new area of science and engineering that makes use of microbially induced calcite precipitation, a type of biocementation technique to improve the geotechnical properties of soil. The process of calcite precipitation is influenced by the production of microbial urease enzyme. Microbially induced calcite precipitation implementation as an established ground improvement method has been partially limited by the need for highly active urease producers and improved injection procedures. This paper discusses the collaborative efforts between the Science and Civil Engineering departments towards developing cross-disciplinary research Master programmes. The aim of the Master of Science research was to isolate highly active ureolytic bacteria from the limestone caves of Sarawak and to conduct comparative biocement test using the isolated ureolytic bacteria, alongside bacterial consortia, negative and positive controls. The best yielding isolates would then be further evaluated by a Master of Engineering student in large scale trials. In the Master of Science research activities, soil samples were collected from limestone caves of Sarawak, then enriched for highly active ureolytic bacteria before being assessed in small-scale biocementation experiments. Poorly graded soils were treated with locally isolated ureolytic bacteria and the surface strength of the treated soil samples were measured with a pocket penetrometer. The test showed that biocementation using the selected ureolytic bacteria can significantly improve the engineering properties of poorly graded soils. However, the efficiency of the microbially induced calcite precipitation process in improving the soil strength varied among the samples which were treated with different isolates, bacterial consortia, and the control strain. The findings in this study suggest that the locally isolated ureolytic bacteria have the potential to be used as alternative microbially induced calcite precipitation agents for biocement applications. This paper demonstrates developing a postgraduate research programme through the collaboration between the different disciplines of biotechnology and engineering.

A thermodynamic model is developed for the calculation of both phase and speciation equilibrium in the H2O-CO2-NaCl-CaCO3-CaSO4 system from 25-250 oC, and from 1 to 1000 bar with NaCl concentrations up to the saturation of halite. The vapor-liquid-solid (calcite, gypsum, anhydrite and halite) equilibrium together with the chemical equilibrium of H+, Na+, Ca2+, CaHCO3+, Ca(OH)+, OH-, Cl-, HCO3-, HSO4-, SO42-, CO32-, CO2(aq), CaCO3(aq) and CaSO4(aq) in the aqueous liquid phase as a function of temperature,  pressure and salt concentrations can be calculated with accuracy close to the experimental results.
Based on this model validated from experimental data, it can be seen that temperature, pressure and salinity all have significant effects on pH, alkalinity and speciations of aqueous solutions and on the solubility of calcite, halite, anhydrite and gypsum. The solubility of anhydrite and gypsum will decrease as temperature increases (e.g. the solubility will decrease by 90% from 360 K to 460 K). The increase of pressure may increase the solubility of sulphase minerals (e.g. gypsum solubility increases by about 20-40% from vapor pressure to 600 bar). Addition of NaCl to the solution may increase mineral solubility up to about 3 molality of NaCl, adding more NaCl beyond that may slightly decrease its solubility. Dissolved CO2 in solution may decrease the solubility of minerals. The influence of dissolved calcite on the solubility of gypsum and anhydrite can be ignored, but dissolved gypsum or anhydrite has a big influence on the calcite solubility. Online calculation is made available on www.geochem-model.org/model.

Tujuan dari penelitian ini adalah untuk mengeksplorasi konsep baru mengenai self-healing dengan menggunakan jamur sebagai agen self-healing yang mampu mendorong terjadinya pengendapan mineral kalsium untuk mengisi retakan pada beton. Meskipun banyak jamur telah dilaporkan mampu mendorong terjadinya mineralisasi kalsium, belum dilakukan investigasi mengenai aplikasi proses tersebut pada perbaikan beton, sehingga pemilahan awal pada berbagai spesies jamur telah dilakukan. Hasil eksperimen menunjukkan bahwa, sebagai akibat dari pelelehan Ca(OH)2 dari beton, pH dari medium pertumbuhan meningkat dari 6.5 sampai 13.0. Meskipun terjadi peningkatan pH secara drastis, spora Trichoderma reesei (ATCC13631) tetap dapat berkecambah menjadi miselium dan bertumbuh secara sama baiknya, entah ada maupun tidak ada beton. Teknik karakterisasi material digunakan pada penelitian ini, seperti difraksi sinar X dan scanning electron microscope (SEM), keduanya membuktikan bahwa kristal yang diendapkan dari hifa jamur tersusun atas kalsit.

Banded marbles constitute a distinct unit of the Hatta metamorphic soLe in the Northern Oman Mountains. The pure and impure marbles were studied petrographicalLy and geochemicaLly to determine their geochemical characterstics and decipher the metamorphic history and variations in their protoliths mineralogy. The marbles are made up mainly of calcite beside pelitic and feldspathic phases. Authigenic albite, with the peculiar "Roe Tourne twinning", is recorded in the marble samples. Crystal and twin morphologies of the calcite define a spectrum that corresponds to increasing temperature from thin twins at very low temperatures to straight thick twins and finally to recrystalLization at grain boundaries at high temperatures. All the components necessary for albite authigenesis during metamorphism are supplied by the host rocks. Microstylolites with filling materials are recorded in the marbles; the latter are the product of metamorphic reactions between the detritus and the host rock component (calcite). The metamorphic rocks in the study area show polyphase deformation, mylonitic fabrics, foliation, stretching Lineation and folding. The sub-ophiolite metamorphic sole and the upper sedimentary melange (Hawasina Complex) comprise a distinct thrust slice in the Hatta area. The absence or rarity exposures of amphibolites in the Hatta zone may be attributed to the higher level of detachment of the basement blocks during the initial separation from the oceanic crust. Trace elements and REE contents are lower in the pure marbles as compared to in the impure (siliceous) marbles. This is attributed mostly to the concentration of REE in the clay fractions and the authigenic Fe-Mn coats of sediment grains rather than concentration in heavy minerals such as zircon. The marbles show a relatively flat REE normalized pattern with no to fair negative Ce anomaly and positive Eu anomaly. The presence of a positive Eu anomaLy is consistent with the authigenic pLagioclase enrichment. The (La/Yb), values of the studied marbles are similar to the average vaLues recorded for the Arabian Sea limestone and the Indian ocean carbonates. Evidently, the banded marbles are metamorphosed "Oman Exotic" limestone which crop out within imbricated thrust sheets of the Hatta metamorphic soLebeneath the Semail ophiolite .

In this study we investigate carbon isotope fractionation during the crystallization of biogenic calcium carbonate. Several species of earthworm including Lumbricus terrestris secrete CaCO 3. Initially a milky fluid comprising micro-spherules of amorphous CaCO 3 (ACC) is secreted into pouches of the earthworm calciferous gland. The micro-spherules coalesce and crystalize to form millimetre scale granules, largely comprising calcite. These are secreted into the earthworm intestine and from there into the soil. L. terrestris were cultured for 28 days in two different soils, moistened with three different mineral waters at 10, 16 and 20 C. The milky fluid in the calciferous glands, granules in the pouches of the calciferous glands and granules excreted into the soil were collected and analysed by FTIR spectroscopy to determine the form of CaCO 3 present and by IRMS to determine d 13 C values. The milky fluid was ACC. Granules removed from the pouches and soil were largely calcite; the granules removed from the pouches contained more residual ACC than those recovered from the soil. The d 13 C values of milky fluid and pouch granules became significantly more negative with increasing temperature (p 0.001). For samples from each temperature treatment, d 13 C values became significantly (p 0.001) more negative from the milky fluid to the pouch granules to the soil granules (À13.77, À14.69 and À15.00 respectively at 10 C; À14.37, À15.07 and À15.18 respectively at 16 C and À14.89, À15.41 and À15.65 respectively at 20 C). Fractionation of C isotopes occurred as the ACC recrystallized to form calcite with the fraction-ation factor ε calcite-ACC ¼ À1.20 ± 0.52‰. This is consistent with the crystallization involving dissolution and reprecipitation rather than a solid state rearrangement. Although C isotopic fractionation has previously been described between different species of dissolved inorganic carbon and various CaCO 3 polymorphs, this is the first documented evidence for C isotope fractionation between ACC and the calcite it recrystallizes to. This phenomenon may prove important for the interpretation of CaCO 3-based C isotope environmental proxies.

Calcareous objects (including ceramics) are frequent in heritage collections. During storage and display they are affected by traces of acetic acid emitted by wood. Depending on the presence of other anions from the environment, a number of calcium acetate phases are formed, many of which are not well characterised. Single crystals suitable for routine crystal structure determination are often not available. Despite the loss of directional information, however, even high-precision measurement of the diffraction of microcrystalline powders contains enough information to determine crystal structures with modern sophisticated software-based evaluation methods. Their application, generally useful in many fields of conservation science, is exemplified here for calcium acetate compounds. Reference data derived from the structure allow easy identification and quantification in mixtures. Occurring phases can hint at storage conditions and former treatments, thereby adding to an object's 'biography'. Identification of efflorescence may be a guide to future prevention.

Lime plaster and mortar are pyrotechnological materials that have been employed in constructions since prehistoric times. They may nucleate as calcite and/or aragonite under different environmental settings. In nature, aragonite and calcite form through biogenic and geogenic processes that lead to different degrees of atomic order. The latter is a result of defects in the crystal lattice, which affect the properties of crystals, including their interaction with infrared light. Using Fourier transform infrared spectrometry (FTIR) with the KBr pellet method, it is possible to exploit these differences and assess the degree of atomic order of aragonite and calcite crystals and thus their mechanisms of formation. Here we use FTIR to characterize the degree of short-range atomic order of a pyrogenic form of aragonite recently observed in experimental and archaeological lime binders. We show that pyrogenic aragonite has a unique signature that allows its identification in archaeological sediments and lime binders of unknown origin. Based on these results, we developed a new FTIR-based method to assess the integrity and degree of preservation of aragonite and calcite when they occur together in the same material. This method allowed a better assessment of the diagenetic history of an archaeological plaster and finds application in the characterization of present-day conservation materials, such as lime plaster and mortar, where different polymorphs may nucleate and undergo recrystallization processes that can alter the mechanical properties of binders.

Fox River water was supersaturated with respect to calcite; natural organic matter (NOM) might play a key role in this phenomenon. Fox River NOM (FRNOM) adsorption on the calcite surface is probably an important mechanism to explain this condition. Fox River water contained moderate ultraviolet absorbance (UVA) of NOM (0.19 1/cm), high concentration of calcium (70 mg/L), suspended solids with relatively high specific surface area (SSA) (6.9 m2/g), and moderate pH value (8.4) based on historical data. To test whether the phenomenon was caused by NOM adsorption, a series of experiments was conducted to explore the interaction between NOM and calcite in conditions similar to those of the Fox River. Suwannee River NOM (SRNOM) and Nordic Reservoir NOM (NRNOM) were used as surrogate NOM. The results show that SRNOM inhibited calcite dissolution significantly after 10 min based on measuring of the decrease in the free calcium concentration. The decrease in the free calcium was not solely due to formation of NOM-calcium complexes, because these complexes made up only about 3% of the total free calcium concentration. Therefore, NOM adsorption onto calcite was probably largely responsible for the inhibited calcite activity. Experimental results also showed that NOM adsorption increased with increasing NOM concentration in the range from 2 to 14 mg NOM/L, which is a common range for river water. Higher charge density also seems to promote sorption onto calcite; relative to NRNOM, SRNOM has a higher charge density and SRNOM has a higher affinity for calcite. Other factors that promoted NOM adsorption onto calcite included higher concentration of calcium and larger SSA of calcite seed. Based on water quality characteristics, the Fox River provides a suitable environment for NOM adsorption on calcite, and it seems likely that Fox River NOM (FRNOM) adsorption on calcite can inhibit calcite precipitation. This understanding of interaction between NOM and calcite could be used by WTPs along the Fox River for better optimization and improvement in treatment and operation

Understanding the mechanism and kinetics of the replacement of carbonates by fluorite has 10 application in Earth sciences and engineering. Samples of Carrara marble were reacted with an 11 ammonium fluoride (NH4F) solution for different reaction times and temperatures. The 12 microstructure of the product phase (fluorite) was analyzed using SEM. The kinetics of 13 replacement was monitored using Rietveld analysis of X-ray powder diffraction patterns of the 14 products. After reaction, all samples preserved their size and external morphology (a 15 pseudomorphic replacement). The grain boundaries of the original marble were preserved 16 although each calcite grain was replaced by multiple fine crystals of fluorite creating inter-crystal 17 porosity. The empirical activation energy Ea (kJ/mol) of the replacement reaction was 18 determined by both model-fitting and model-free methods. The isoconversional method yielded 19 an empirical activation energy of 41 kJ/mol, and a statistical approach applied to the model-20 fitting method revealed that the replacement of Carrara marble by fluorite is better fitted to a 21 diffusion-controlled process. These results suggest that the replacement reaction is dependent on 22 the ion diffusion rate in the fluid phase through the newly formed porosity.