DOCSLIB.ORG

Aragonite Formation in Confinements: a Step Toward Understanding Polymorph Control COMMENTARY Yifei Xua,B,C and Nico A

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Aragonite Formation in Confinements: a Step Toward Understanding Polymorph Control COMMENTARY Yifei Xua,B,C and Nico A COMMENTARY Aragonite formation in confinements: A step toward understanding polymorph control COMMENTARY Yifei Xua,b,c and Nico A. J. M. Sommerdijka,b,c,1 Calcium carbonate (CaCO3) is one of the most com- unclear but were generally attributed to the interac- mon minerals on Earth; it not only forms rocks like tion between the acidic functional groups of the limestone or marble but is also a main component of biomacromolecules and the mineral components. Ad- biominerals such as pearls, the nacre of seashells, and ditionally, it was reported that a macromolecular sea-urchin skeletons (1). Despite many years of re- hydrogel-like 3D network is formed before the miner- search, the polymorphism of CaCO3 is still far from alization of nacre (11), which may play a role in the being understood. CaCO3 has three anhydrous crys- crystallization process by confining the crystallization talline forms: calcite, aragonite, and vaterite, with a to defined small volumes. Nonetheless, confinement decreasing thermodynamic stability under aqueous has never been directly correlated with aragonite for- ambient conditions (calcite > aragonite > vaterite) mation in biominerals, although its capability of con- (2). While vaterite is rare in nature, calcite and arago- trolling crystal orientation and polymorphism has nite are both frequently found in rocks or biominerals been shown in many recent reports (12–15). (1). A well-known example is the aragonite structure of Now, Zeng et al. (5) explore for the first time the nacre (3), where the organization of the crystals leads impact of confinement on aragonite formation. By to extraordinary mechanical performance. However, precipitating CaCO3 within the cylindrical pores of in synthetic systems, crystallization experiments only track-etched membranes (Fig. 1), they investigated generate a small fraction of aragonite compared with the relationship between pore size and the polymor- calcite at ambient conditions and in the absence of phism of CaCO3. Strikingly, a high level of aragonite additives (4). So, how is the formation of aragonite formation was detected within these nanosized con- + facilitated in nature, especially in biominerals? In finements. Using the same concentrations of Mg2 2− PNAS, Zeng et al. (5) shed light on this matter by and SO4 as additives, the aragonite proportion in showing that aragonite formation is dramatically pro- bulk solution was only 7%, while this value increased moted within confinements. to 69% in 200-nm pores and reached 100% in 50-nm In recent decades, great efforts have been spent pores. When even smaller pores were used (25 nm), toward understanding the strategies exploited by pure aragonite crystals were obtained even in the ab- organisms to regulate aragonite formation, and sev- sence of any additives. More than that, the aragonite eral key factors have been identified. Up to now, the crystallized within these nanopores was mainly single + effect of Mg2 additive is the most well established. crystal rods, highly oriented along the c-axis. + Mg2 is abundant in seawater and is expected to be The authors subsequently examined several possi- present during the formation of many marine biomin- ble origins for the preferred formation of aragonite + + erals (6, 7). At high Mg2 :Ca2 ratios, aragonite forms within these confinements. Confinement is known to as the major crystalline form instead of calcite at room increase the incubation time for crystallization nucle- temperature. This was recently explained by Sun et al. ation, inhibiting the formation of thermodynamically + (8), who show that Mg2 can significantly increase the stable phases (e.g., calcite) in favor of metastable surface energy of calcite and raise its nucleation bar- phases (13). This is, however, not likely the reason for rier, while aragonite is much less affected. Meanwhile, aragonite formation here, since aragonite is seldom insoluble organic matrices and soluble acidic macro- seen as a precursor to calcite. Computations demon- molecules extracted from aragonite-forming tissues strated that the reaction was also not affected by a also favor aragonite formation to different extents variation of diffusion rates. Hence, the only reasonable (9, 10). Detailed mechanisms of the effects remain cause for the promotion of aragonite formation seems aLaboratory of Materials and Interface Chemistry, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands; bCenter for Multiscale Electron Microscopy, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands; and cInstitute for Complex Molecular Systems, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands Author contributions: Y.X. and N.A.J.M.S. wrote the paper. The authors declare no conflict of interest. Published under the PNAS license. See companion article on page 7670 in issue 30 of volume 115. 1To whom correspondence should be addressed. Email: [email protected]. Published online August 3, 2018. www.pnas.org/cgi/doi/10.1073/pnas.1811696115 PNAS | August 21, 2018 | vol. 115 | no. 34 | 8469–8471 Downloaded by guest on September 27, 2021 Fig. 1. Scheme of CaCO3 crystallization within the cylindrical nanopores of track-etched membranes. While crystals formed in the bulk solution are mainly calcite, aragonite single crystals oriented in the c-axis are formed within the nanopores. to be the influence of the pore surface on crystal nucleation. In- ∼500-nm-thick aragonite layers (17). As this dimension is still a bit deed, aragonite formation was further promoted when smaller above the largest effective pore size (200 nm) reported by Zeng pores were used and larger pore surfaces were generated. Zeng et al. (5), it is likely that in addition to confinement also the in- et al. (5) suggest that the pore surface may modulate ion activity teraction between the mineral and biomacromolecular matrix (9– and thus facilitate aragonite formation. Unfortunately, experimen- 11) plays a role in the preferred aragonite formation in nacre. tal confirmation was hindered by the difficulty in directly measur- A similar fundamental question remains on how confinement is ing the ionic profiles within the nanopores. correlated to the selection of the aragonite polymorph. Zeng et al. By showing that pure aragonite single crystals can be synthe- (5) show that the two main volume effects of confinement, that is, sized at ambient conditions by using only nanosized confinements, inhibiting nucleation and limiting diffusion rate, are both irrelevant the work of Zeng et al. (5) provides a route for CaCO3 polymorph to the preferred aragonite formation, and the main role of con- control that may possibly also be applied by biomineralizing organ- finement appears to be enhancing the surface effect. Indeed, isms. In particular, it points to the importance of surface effects in when track-etched membranes from different manufacturers were controlling aragonite formation. This also aligns with the computa- used, different CaCO3 polymorphs formed within pores of the + tional work of Sun et al. (8) showing that the presence of Mg2 same size (15). This was attributed to possible differences in the favors aragonite formation by modulating the surface energy of density or conformation of the chemical species lining the mem- the crystals. Nevertheless, the details of the mechanism by which brane pores, as only minor differences of surface roughness and surface effects facilitate aragonite growth for now remain unknown. no differences in composition were detected for these mem- The surface interactions may modulate the CaCO3 polymorph branes. Hence, maybe not only aragonite but also other poly- through tuning the distribution of ions, as proposed by the authors; morphs of CaCO3 can be selected by nanosized confinements alternatively, the effect may be due to a lower interfacial energy with the appropriate surface chemistry. This could certainly be a between the pore surface and aragonite, compared with calcite. strategy employed in biomineralization but could also potentially Another intriguing question is how the confinement promotes the provide a new window for controlling polymorphism in the syn- formation of oriented single crystals, as was also reported for other thesis of crystalline materials. In conclusion, the results of Zeng mineral systems (14–16). Clearly, future investigations of crystalliza- et al. (5) are of great significance for the understanding of poly- tion within porous membranes are likely to give us more important morph control, which has seen some recent interesting advances insights into the control of crystal orientation and polymorphism (18, 19) but is still in its infancy despite its importance, in particular with possible relevance for both synthetic and biological systems. in the preparation of pharmaceuticals. Meanwhile, to what extent organisms indeed deploy nano- sized confinements to promote aragonite formation is a question Acknowledgments that needs further discussion. One interesting system is nacre, This work was supported by a TOP-PUNT grant from the Netherlands Organi- where lamellar organic matrices were found between adjacent zation of Scientific Research. 1 Lowenstam HA, Weiner S (1989) On Biomineralization (Oxford Univ Press, New York). 2 Plummer LN, Busenberg E (1982) The solubilities of calcite, aragonite and vaterite in CO2-H2O solutions between 0 and 90 C, and an evaluation of the aqueous model for the system CaCO3-CO2-H2O. Geochim Cosmochim Acta 46:1011–1040. 3 Jackson A, Vincent JF, Turner R (1988) The mechanical design of nacre. Proc R Soc Lond B Biol Sci 234:415–440. 4 Ogino T, Suzuki T, Sawada K (1987) The formation and transformation mechanism of calcium carbonate in water. Geochim Cosmochim Acta 51:2757–2767. 5 Zeng M, et al. (2018) Confinement generates single-crystal aragonite rods at room temperature. Proc Natl Acad Sci USA 115:7670–7675. 8470 | www.pnas.org/cgi/doi/10.1073/pnas.1811696115 Xu and Sommerdijk Downloaded by guest on September 27, 2021 6 Morse JW, Wang Q, Tsio MY (1997) Influences of temperature and Mg:Ca ratio on CaCO3 precipitates from seawater. Geology 25:85–87.
Load more

Recommended publications
  • Non-Aqueous Formation of the Calcium Carbonate Polymorph Vaterite: Astrophysical Implications Sarah J
    Astronomy & Astrophysics manuscript no. vaterite_FINAL c ESO 2021 August 9, 2021 Non-aqueous formation of the calcium carbonate polymorph vaterite: astrophysical implications Sarah J. Day1;2, Stephen P. Thompson2, Julia E. Parker2, and Aneurin Evans1 1 Astrophysics Group, Keele University, Keele, Staffordshire, UK, ST5 5BG 2 Diamond Light Source, Harwell Science and Innovation Campus, Chilton, Didcot, Oxon OX11 0QX Preprint online version: August 9, 2021 ABSTRACT Aims. To study the formation of calcium carbonate, through the solid-gas interaction of amorphous Ca-silicate with gaseous CO2, at elevated pressures, and link this to the possible presence of calcium carbonate in a number of circum- stellar and planetary environments. Methods. We use in-situ synchrotron X-Ray powder diffraction to obtain detailed structural data pertaining to the formation of the crystalline calcium carbonate phase vaterite and its evolution with temperature. Results. We found that the metastable calcium carbonate phase vaterite was formed alongside calcite, at elevated CO2 pressure, at room temperature and subsequently remained stable over a large range of temperature and pressure. Conclusions. We report the formation of the calcium carbonate mineral vaterite whilst attempting to simulate carbon- ate dust grain formation in astrophysical environments. This suggests that vaterite could be a mineral component of carbonate dust and also presents a possible method of formation for vaterite and its polymorphs on planetary surfaces. Key words. Astrochemistry | ISM: dust | Methods: laboratory | Planets and satellites: surfaces 1. Introduction NGC6537. They argue that the carbonates in these envi- ronments require formation by non-aqueous routes, such 1.1. Carbonates in astrophysical environments as gas-phase condensation or processes on grain surfaces.
    [Show full text]
  • Infrare D Transmission Spectra of Carbonate Minerals
    Infrare d Transmission Spectra of Carbonate Mineral s THE NATURAL HISTORY MUSEUM Infrare d Transmission Spectra of Carbonate Mineral s G. C. Jones Department of Mineralogy The Natural History Museum London, UK and B. Jackson Department of Geology Royal Museum of Scotland Edinburgh, UK A collaborative project of The Natural History Museum and National Museums of Scotland E3 SPRINGER-SCIENCE+BUSINESS MEDIA, B.V. Firs t editio n 1 993 © 1993 Springer Science+Business Media Dordrecht Originally published by Chapman & Hall in 1993 Softcover reprint of the hardcover 1st edition 1993 Typese t at the Natura l Histor y Museu m ISBN 978-94-010-4940-5 ISBN 978-94-011-2120-0 (eBook) DOI 10.1007/978-94-011-2120-0 Apar t fro m any fair dealin g for the purpose s of researc h or privat e study , or criticis m or review , as permitte d unde r the UK Copyrigh t Design s and Patent s Act , 1988, thi s publicatio n may not be reproduced , stored , or transmitted , in any for m or by any means , withou t the prio r permissio n in writin g of the publishers , or in the case of reprographi c reproductio n onl y in accordanc e wit h the term s of the licence s issue d by the Copyrigh t Licensin g Agenc y in the UK, or in accordanc e wit h the term s of licence s issue d by the appropriat e Reproductio n Right s Organizatio n outsid e the UK. Enquirie s concernin g reproductio n outsid e the term s state d here shoul d be sent to the publisher s at the Londo n addres s printe d on thi s page.
    [Show full text]
  • Synthesis Methods and Favorable Conditions for Spherical Vaterite Precipitation: a Review
    crystals Review Synthesis Methods and Favorable Conditions for Spherical Vaterite Precipitation: A Review Donata Konopacka-Łyskawa Department of Process Engineering and Chemical Technology, Faculty of Chemistry, Gda´nskUniversity of Technology, Narutowicza 11/12, 80-233 Gda´nsk,Poland; [email protected]; Tel.: +48-58-347-2910 Received: 15 March 2019; Accepted: 18 April 2019; Published: 25 April 2019 Abstract: Vaterite is the least thermodynamically stable anhydrous calcium carbonate polymorph. Its existence is very rare in nature, e.g., in some rock formations or as a component of biominerals produced by some fishes, crustaceans, or birds. Synthetic vaterite particles are proposed as carriers of active substances in medicines, additives in cosmetic preparations as well as adsorbents. Also, their utilization as a pump for microfluidic flow is also tested. In particular, vaterite particles produced as polycrystalline spheres have large potential for application. Various methods are proposed to precipitate vaterite particles, including the conventional solution-solution synthesis, gas-liquid method as well as special routes. Precipitation conditions should be carefully selected to obtain a high concentration of vaterite in all these methods. In this review, classical and new methods used for vaterite precipitation are presented. Furthermore, the key parameters affecting the formation of spherical vaterite are discussed. Keywords: vaterite; calcium carbonate; polymorph; precipitation; synthesis; carbonation 1. Introduction Vaterite is the least thermodynamically stable anhydrous calcium carbonate polymorph and it easily transforms into more stable calcite or aragonite in the presence of water. This form of calcium carbonate mineral was named to honor the German chemist and mineralogist, Heinrich Vater, in 1903.
    [Show full text]
  • Bacterially Mediated Mineralization of Vaterite
    Geochimica et Cosmochimica Acta 71 (2007) 1197–1213 www.elsevier.com/locate/gca Bacterially mediated mineralization of vaterite Carlos Rodriguez-Navarro a,*, Concepcion Jimenez-Lopez b, Alejandro Rodriguez-Navarro a, Maria Teresa Gonzalez-Mun˜oz b, Manuel Rodriguez-Gallego a a Departamento de Mineralogı´a y Petrologı´a, Universidad de Granada, Fuentenueva s/n, 18002 Granada, Spain b Departamento de Microbiologı´a, Universidad de Granada, Fuentenueva s/n, 18002 Granada, Spain Received 4 May 2006; accepted in revised form 27 November 2006 Abstract Myxococcus xanthus, a common soil bacterium, plays an active role in the formation of spheroidal vaterite. Bacterial production of þ À CO2 and NH3 and the transformation of the NH3 to NH4 and OH , thus increasing solution pH and carbonate alkalinity, set the phys- icochemical conditions (high supersaturation) leading to vaterite precipitation in the microenvironment around cells, and directly onto the surface of bacterial cells. In the latter case, fossilization of bacteria occurs. Vaterite crystals formed by aggregation of oriented nano- crystals with c-axis normal to the bacterial cell-wall, or to the core of the spherulite when bacteria were not encapsulated. While preferred orientation of vaterite c-axis appears to be determined by electrostatic affinity (ionotropic effect) between vaterite crystal (0001) planes and the negatively charged functional groups of organic molecules on the bacterium cell-wall or on extracellular polymeric substances (EPS), analysis of the changes in the culture medium chemistry as well as high resolution transmission electron microscopy (HRTEM) observations point to polymorph selection by physicochemical (kinetic) factors (high supersaturation) and stabilization by organics, both connected with bacterial activity.
    [Show full text]
  • What Can a Diffraction Pattern Tell You About Your Sample?
    What can a diffraction pattern tell you about your sample? A diffraction pattern is like a ‘fingerprint’ and can be used to identify what crystals are present in your sample. Although calcite and vaterite both consist of calcium carbonate (they have the same chemical formula, CaCO3) the atoms are arranged differently in each structure – we call these polymorphs. 2- The crystal structures of calcite and vaterite are shown below. In the carbonate group (CO3 ) the oxygens are arranged in the 3 corners of a triangle, each bonded to the carbon in the centre. Both structures are made up of alternating layers of calcium and carbonate. Have a good look at the arrangements of the layers and see if you can describe the differences between the calcite and vaterite structures, before reading the summary in the table below! Don’t worry if you find the differences hard to see – it is very difficult to try and represent 3D crystal structures as 2D drawings! A view of the crystal structure of calcite A view of the crystal structure of vaterite Ca = green, C = black and O = red. Ca = green, C = black and O = red. Calcite Vaterite Orientation of Lie flat in the layer Stand perpendicular to the carbonate layers groups in the layers Calcium layer The Ca in a layer is offset from The Ca in a layer sits in the stacking those in the layers above and same position as those in the below. There is an ABCABC Ca layers above and below. layer stacking Carbonate layer Alternate carbonate layers have Alternate carbonate layers have stacking the carbonate triangle pointing
    [Show full text]
  • Characteristics and Crystal Structure of Calcareous Deposit Films Formed by Electrodeposition Process in Artificial and Natural Seawater
    coatings Article Characteristics and Crystal Structure of Calcareous Deposit Films Formed by Electrodeposition Process in Artificial and Natural Seawater Jun-Mu Park 1, Myeong-Hoon Lee 1 and Seung-Hyo Lee 2,* 1 Division of Marine Engineering, Korea Maritime and Ocean University, Busan 49112, Korea; [email protected] (J.-M.P.); [email protected] (M.-H.L.) 2 Department of Ocean Advanced Materials Convergence Engineering, Korea Maritime and Ocean University, Busan 49112, Korea * Correspondence: [email protected] Abstract: In this study, we tried to form the calcareous deposit films by the electrodeposition process. The uniform and compact calcareous deposit films were formed by electrodeposition process and their crystal structure and characteristics were analyzed and evaluated using various surface analytical techniques. The mechanism of formation for the calcareous deposit films could be confirmed and the role of magnesium was verified by experiments in artificial and natural seawater solutions. The highest amount of the calcareous deposit film was obtained at 5 A/m2 while current densities between 1–3 A/m2 facilitated the formation of the most uniform and dense layers. In addition, the adhesion characteristics were found to be the best at 3 A/m2. The excellent characteristics of the calcareous deposit films were obtained when the dense film of brucite-Mg(OH)2 and metastable aragonite-CaCO3 was formed in the appropriate ratio. Citation: Park, J.-M.; Lee, M.-H.; Lee, Keywords: electrodeposition process; calcareous deposit films; aragonite crystal structure; seawater S.-H. Characteristics and Crystal Structure of Calcareous Deposit Films Formed by Electrodeposition Process in Artificial and Natural Seawater.
    [Show full text]
  • Crystal Growth Mechanism of Vaterite in the Systems Containing Charged Synthetic Poly(Amino Acids)
    ORIGINAL SCIENTIFIC PAPER Croat. Chem. Acta 2017, 90(4), 689–698 Published online: 19 April 2018 DOI: 10.5562/cca3290 Crystal Growth Mechanism of Vaterite in the Systems Containing Charged Synthetic Poly(Amino Acids) Branka Njegić Džakula,1,* Giuseppe Falini,2 Damir Kralj1,# 1 Laboratory for Precipitation Processes, Division of Materials Chemistry, Ruđer Bošković Institute, Bijenička cesta 54, HR-10000 Zagreb, Croatia 2 Dipartimento di Chimica "Giacomo Ciamician", Universitá di Bologna, Via Selmi 2, 40126 Bologna, Italy * Corresponding author’s e-mail address: [email protected] # Corresponding author’s e-mail address: [email protected] RECEIVED: January 18, 2018 REVISED: April 17, 2018 ACCEPTED: April 17, 2018 THIS PAPER IS DEDICATED TO PROF. MLADEN ON THE OCCASION OF HIS 70TH BIRTHDAY ŽINIĆ Abstract: Negatively ionisable poly-L-glutamic acid (pGlu) and poly-L-aspartic acid (pAsp), considered as analogues of the naturally occurring acidic macromolecules involved in biomineralization processes, were used as additives in the calcium carbonate precipitation systems in order to investigate their interactions with the vaterite crystallites. Poly-L-lysine (pLys), a positively ionisable poly(amino acid), was also used in order to elucidate the impact of the side chain charge. The growth kinetics of vaterite was found parabolic, indicating that the integration of growth units into the spiral step at the vaterite crystal surfaces is the rate-determining mechanism. The presence of small amounts of pGlu and pAsp inhibited the crystal growth. At the highest concentrations of both acidic macromolecules the exponential rate law was observed, which indicates the surface nucleation as the rate controlling mechanism. The addition of pLys in the range of applied concentrations did not significantly influence the crystal growth of the vaterite.
    [Show full text]
  • ACC and Vaterite As Intermediates in the Solution-Based Crystallization of Caco3
    Chapter 5 ACC and Vaterite as Intermediates in the Solution-Based Crystallization of CaCO3 Juan Diego Rodriguez-Blanco, Karina K. Sand, and Liane G. Benning 5.1 Introduction Calcium carbonate minerals are ubiquitous on Earth where they play a key role in many marine and terrestrial biomineralization processes (e.g., see also Chap. 9 by Falini and Fermani in this book). Their ubiquitous nature makes them key players in controlling a large part of the global carbon cycle. At ambient temperatures, they very often crystallize from solution via two intermediate phases: amorphous calcium carbonate (ACC) and vaterite. ACC is a poorly ordered material (50–500 nm) (Rodriguez-Blanco et al. 2008) that in its pure form (no other cations but Ca2C present at formation) consist of a Ca-rich framework with 1-nm diameter interconnected pores that contain water and carbonate ions (Goodwin et al. 2010). In recent years, ACC has been shown to J.D. Rodriguez-Blanco () Department of Geology, Trinity College Dublin, Dublin 2, Ireland NanoScience Center, Department of Chemistry, University of Copenhagen, Copenhagen, Denmark e-mail: [email protected]; [email protected] K.K. Sand NanoScience Center, Department of Chemistry, University of Copenhagen, Copenhagen, Denmark Physical Sciences Division, Pacific Northwest National Laboratories, Richland, WA, USA L.G. Benning German Research Center for Geosciences, GFZ, Interface Geochemistry Section, 14473 Potsdam, Germany Department of Earth Sciences, Free University of Berlin, 12249 Berlin, Germany School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK © Springer International Publishing Switzerland 2017 93 A.E.S. Van Driessche et al.
    [Show full text]
  • The Crystallization Process of Vaterite Microdisc Mesocrystals Via Proto-Vaterite Amorphous Calcium Carbonate Characterized by Cryo-X-Ray Absorption Spectroscopy
    crystals Communication The Crystallization Process of Vaterite Microdisc Mesocrystals via Proto-Vaterite Amorphous Calcium Carbonate Characterized by Cryo-X-ray Absorption Spectroscopy Li Qiao 1, Ivo Zizak 2, Paul Zaslansky 3 and Yurong Ma 1,* 1 School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China; [email protected] 2 Department Structure and Dynamics of Energy Materials, Helmholtz-Zentrum-Berlin, 14109 Berlin, Germany; [email protected] 3 Department for Operative and Preventive Dentistry, Charité-Universitätsmedizin Berlin, 10117 Berlin, Germany; [email protected] * Correspondence: [email protected] Received: 27 July 2020; Accepted: 23 August 2020; Published: 26 August 2020 Abstract: Investigation on the formation mechanism of crystals via amorphous precursors has attracted a lot of interests in the last years. The formation mechanism of thermodynamically meta-stable vaterite in pure alcohols in the absence of any additive is less known. Herein, the crystallization process of vaterite microdisc mesocrystals via proto-vaterite amorphous calcium carbonate (ACC) in isopropanol was tracked by using Ca K-edge X-ray absorption spectroscopy (XAS) characterization under cryo-condition. Ca K-edge X-ray absorption near edge structure (XANES) spectra show that the absorption edges of the Ca ions of the vaterite samples with different crystallization times shift to lower photoelectron energy while increasing the crystallization times from 0.5 to 20 d, indicating the increase of crystallinity degree of calcium carbonate. Ca K-edge extended X-ray absorption fine structure (EXAFS) spectra exhibit that the coordination number of the nearest neighbor atom O around Ca increases slowly with the increase of crystallization time and tends to be stable as 4.3 ( 1.4).
    [Show full text]
  • Vaterite Caco3 C 2001-2005 Mineral Data Publishing, Version 1
    Vaterite CaCO3 c 2001-2005 Mineral Data Publishing, version 1 Crystal Data: Hexagonal. Point Group: 6/m 2/m 2/m. As very finely fibrous crystals, to 0.1 mm, typically in spherulitic aggregates. Physical Properties: Hardness = n.d. D(meas.) = 2.54 D(calc.) = 2.65 Optical Properties: Semitransparent. Color: Colorless. Optical Class: Uniaxial (+). ω = 1.550 = 1.644–1.650 Cell Data: Space Group: P 63/mmc. a = 7.135 c = 8.524 Z = 6 X-ray Powder Pattern: Synthetic. 3.30 (100), 2.73 (95), 1.823 (70), 2.065 (60), 3.57 (55), 1.858 (25), 1.647 (25) Chemistry: (1) Identification depends on correspondence of the X-ray powder pattern with that of synthetic material. Polymorphism & Series: Trimorphous with aragonite and calcite; metastable below ∼400 ◦C. Occurrence: A major constituent of a carbonated calcium silicate hydrogel complex formed from larnite (Ballycraigy, Ireland); a rock-forming mineral formed at low temperatures by hydration of metamorphic calc-silicate rocks in the presence of atmospheric CO2, in slightly metamorphosed marls and conglomerates, and in weathering crusts (Hatrurim Formation, Israel). Association: Calcite, aragonite, tobermorite, hydrogarnet, kaolinite (Hatrurim Formation, Israel). Distribution: From Ballycraigy, Larne, Co. Antrim, Ireland. At the Bellerberg and Emmelberg volcanoes, Eifel district, Germany. From Hopffeldboden, Salzburg, Austria. At Mont Saint-Hilaire, Quebec, Canada. From the Wessels mine, near Kuruman, Cape Province, South Africa. In the Hatrurim Formation, Israel. At Liawenee, near Great Lake, Tasmania, Australia. From the McMurdo area, Antarctica. Name: To honor Heinrich Vater (1859–1930), Professor of Mineralogy and Chemistry, Tharandt, Germany. Type Material: n.d.
    [Show full text]
  • New Aragonite 87Sr/86Sr Records of Mesozoic Ammonoids and Approach to the Problem of N, O, C and Sr Isotope Cycles in the Evolution of the Earth” by Yuri D
    VOLUMINA JURASSICA, 2018, XVI (1): – Comments on “New aragonite 87Sr/86Sr records of Mesozoic ammonoids and approach to the problem of N, O, C and Sr isotope cycles in the evolution of the Earth” by Yuri D. Zakharov, Sergei I. Dril, Yasunari Shigeta, Alexander M. Popov, Eugenij Y. Baraboshkin, Irina A. Michailova and Peter P. Safronov [Sedimentary Geology, 364 (2018): 1–13] Mikhail A. ROGOV1 Keywords: ammonoids, Sr isotopes, erroneous determination. Abstract. Comments are provided on a published paper on 87Sr/86Sr records of Mesozoic ammonoids [Yuri D. Zakharov, Sergei I. Dril, Yasunari Shigeta, Alexander M. Popov, Eugenij Y. Baraboshkin, Irina A. Michailova, and Peter P. Safronov, New aragonite 87Sr/86Sr re- cords of Mesozoic ammonoids and approach to the problem of N, O, C and Sr isotope cycles in the evolution of the Earth, Sedimentary Geology, 364 (2018): 1–13], where insufficiently or erroneously dated materials have been used. The names of the Jurassic ammonites used in the discussed article are erroneous, and these names are sometimes allocated wrong stratigraphic and geographic information. For example, “Procerites funatus” from the Callovian of the Ryazan region following its features and mode of preservation should be re-as- signed to the Volgian Kachpurites cheremkhensis from the Yaroslavl area. These problems partly result from the study of specimens deliv- ered from fossil dealers. Therefore, the interpretation of the differences in Lower Albian ammonite Sr isotope values as function of their habitat depths given by these authors should rather be explained by their different geologic age. Due to the significant oscillation of Sr isotope values in marine carbonates through time and the uniformity of the stron- tium isotope compositions of different basins, Sr-isotope chemostratigraphy provides a powerful tool for correlation.
    [Show full text]
  • Refinement of the Crystal Structure of the Aragonite Phase of Caco3
    JOURNAL OF RESEAR CH of the N a tional Bureau of Standards - A. Physics and Chemistry Vol. 75A No. 1, January - February 197 1 Refinement of the Crystal Structure of the Aragonite Phase of CaC0 3 B. Dickens and J. S. Bowen* Institute for Materials Research National Bureau of Standards Washington, D.C . 20234 (July 31, 1970) Arago nit e (C aCO ,,) c ry stalli zes in th e unit cell a = 4.9598(5) /\ . 6 = 7.9641(9) A, and c= 5.7379(6) A at 25 °C with four form ula we ights in space-group Pm cn. The structure has been re fin ed to N".= 0.024. N= 0.040 using 765 x- ray reAections from a sin gJe crystal. The Ca ion is coordinat ed to nin e oxygens with Ca .. ° distances III the range 2.414(2) A to 2.653(1) A. The two un ique C- O di s ta nces in th e CO" group are 1.288(2) ;\ (o n the mirror plan e) and 1. 283(1) A. T he two un ique O- C-o a ngles are 119.6(2 )" (acro ss the mirror plane) and 120.1 3(8)". The dis tances a nd angles in th e CO" "roup are not signifi cantl y d iffe rent at the 95 pe rcent confidence level. " Key word s; Calcium carbonates; carbonates; crystal s tructure; s in gle c rys t.al x- ray diffracti on. 1. Introduction density, 2.944 g ' cm- 3 ; Crystal: material available was heavily twinned; a s ma lJ wedge was th e largest crystal Aragonite (CaCO:d is found in nature as a mineral fragment found whi ch showed no evidence of twinning and is an important biomineral because of its presence under optical and x·ray examination; this wedge was in coral, clam shells, gall stones, and otoliths.
    [Show full text]