In submerged soils and sediments, clay minerals are often exposed to anoxic waters containing ferrous iron (Fe 2+). Here, we investigated the sorption of Fe 2+ onto a synthetic montmorillonite (Syn-1) low in structural Fe (<0.05 mmol Fe per kg) under anoxic conditions and the effects of subsequent oxidation. Samples were prepared at two Fe-loadings (0.05 and 0.5 mol Fe added per kg clay) and equilibrated for 1 and 30 days under anoxic conditions (O 2< 0.1 ppm), followed by exposure to ambient air. Iron solid-phase speciation and mineral identity was analysed by 57Fe Mössbauer spectroscopy and synchrotron X-ray absorption spectroscopy (XAS). Mössbauer analyses showed that Fe( II) was partially oxidized (14–100% of total added Fe 2+) upon sorption to Syn-1 under anoxic conditions. XAS results revealed that the added Fe 2+ mainly formed precipitates (layered Fe minerals, Fe( III)-bearing clay minerals, ferrihydrite, and lepidocrocite) in different quantities depending on the Fe-loading. Exposing the suspensions to ambient air resulted in rapid and complete oxidation of sorbed Fe( II) and the formation of Fe( III)-phases (Fe( III)-bearing clay minerals, ferrihydrite, and lepidocrocite), demonstrating that the clay minerals were unable to protect ferrous Fe from oxidation, even when equilibrated 30 days under anoxic conditions prior to oxidation. Our findings clarify the role of clay minerals in the formation and stability of Fe-bearing solid phases during redox cycles in periodically anoxic environments. K. Lagarec and D. G. Rancourt, Recoil − Mössbauer spectral analysis software for Windows., University of Ottawa, Ottawa, 1998 Search PubMed . D. G. Rancourt and J. Y. Ping, Voigt-based methods for arbitrary-shape static hyperfine parameter distributions in mossbauer-spectroscopy, Nucl. Instrum. Methods Phys. Res., Sect. B, 1991, 58, 85–97 CrossRef .

a b c Środoń, J. (2006). "Chapter 12.2 Identification and Quantitative Analysis of Clay Minerals". Developments in Clay Science. 1: 765–787. doi: 10.1016/S1572-4352(05)01028-7. ISBN 9780080441832. Argillaceous limestone: Mineral information, data and localities". www.mindat.org . Retrieved 2019-12-27. If you’re other than a board gamer or are into board games but also dabble in the odd poker game here or there, or are an ardent participant in those circles, Iron Clays may not be for you.Kerr PF (1952). "Formation and Occurrence of Clay Minerals". Clays and Clay Minerals. 1 (1): 19–32. doi: 10.1346/CCMN.1952.0010104. Rivkin AS, Volquardsen EL, Clark BE (2006). "The surface composition of Ceres: Discovery of carbonates and iron-rich clays" (PDF). Icarus. 185 (2): 563–567. doi: 10.1016/j.icarus.2006.08.022. Andrejkovičová, S.; Velosa, A.L.; Ferraz, E.; Rocha, F. (2014). "Influence of clay minerals addition on mechanical properties of air lime–metakaolin mortars". Construction and Building Materials. 65: 132–139. doi: 10.1016/j.conbuildmat.2014.04.118. Brass: Birmingham features meticulously crafted illustrations by Damien Mammoliti and Mr. Cuddington, elegant graphic design, and high quality components.

For the majority of the samples, the LCF significantly improved when an Fe( III)-containing clay mineral reference (SWy-2, containing 3 wt% Fe) was included as additional reference in the fits. Released Si from Syn-1 after 1 day equilibration between pH 6 and 10 amounted on average to ∼0.016 mmol Si per g clay compared to up to 8 times lower Si concentrations for anoxic sorption samples with Fe (see Fig. S6a and S7 †). This provides additional evidence that the released Si from Syn-1 was removed from solution upon addition of Fe, either by adsorption or incorporation into newly formed Fe phases. It has been suggested by Soltermann et al. 30 that Fe 2+ can be taken up by the clay minerals, leading to the formation of Fe-bearing clay minerals. Subramaniam, Anand Bala; Wan, Jiandi; Gopinath, Arvind; Stone, Howard A. (2011). "Semi-permeable vesicles composed of natural clay". Soft Matter. 7 (6): 2600–2612. arXiv: 1011.4711. Bibcode: 2011SMat....7.2600S. doi: 10.1039/c0sm01354d. S2CID 52253528. As well as the chips themselves, the quality continues through into the transparent blue-ish hued plastic holder and the outer cardboard container. We used to have a bowl of “odd” dice as a centrepiece on our gaming table. But the beauty and versatility of these chips now makes them a permanent feature. One always within reach. Which is perfect as they are nearly always needed (or wanted) whatever we play! T. B. Hofstetter, A. Neumann and R. P. Schwarzenbach, Reduction of nitroaromatic compounds by Fe(II) species associated with iron-rich smectites, Environ. Sci. Technol., 2006, 40, 235–242 CrossRef CAS PubMed . A. P. Zhukhlistov, Crystal structure of lepidocrocite FeO(OH) from the electron-diffractometry data, Crystallogr. Rep., 2001, 46, 730–733 CrossRef .

Components

Brass: Lancashire features meticulously crafted illustrations by Damien Mammoliti and Mr. Cuddington, elegant graphic design, and high quality components. A. Manceau and M. L. Schlegel, Texture effect on polarized EXAFS amplitude, Phys. Chem. Miner., 2001, 28, 52–56 CrossRef CAS .

A lower amount of lepidocrocite was formed in the low Fe-load samples, as direct oxidation of Fe 2+ in presence of elevated Si concentrations (high Si/Fe ratio in solution) may mainly precipitate as ferrihydrite. 73 However, only a small fraction of the sorbed Fe in the oxic samples was formed by direct oxidation of dissolved Fe 2+ for low Fe-loading samples equilibrated at pH ∼8 (between 7 and 12%, see Fig. S4 and S5 †) compared to samples equilibrated at pH ∼7 (between 60 and 65%, see Fig. S4 and S5 †). Nevertheless both low Fe-loading samples resulted in the presence of similar solid phases. The higher fraction of lepidocrocite observed in the high Fe-loading oxic samples as compared to the low Fe-loading samples may be due to the oxidation of dissolved Fe 2+ in the presence of a low Si/Fe ratio in solutions, which favors lepidocrocite formation over ferrihydrite or through the transformation of green rust into lepidocrocite. 66,73 Because only a small fraction of the sorbed Fe (up to 20%, see Fig. S4 and S5 †) was formed by direct oxidation of dissolved Fe 2+ in high Fe-loading samples, lepidocrocite was primarily formed from the transformation of Fe-phases precipitated under anoxic conditions. D. Soltermann, M. Marques Fernandes, B. Baeyens, J. Miehé-Brendlé and R. Dähn, Competitive Fe(II)–Zn(II) uptake on a synthetic montmorillonite, Environ. Sci. Technol., 2014, 48, 190–198 CrossRef CAS PubMed . Given the requirement of water, clay minerals are relatively rare in the Solar System, though they occur extensively on Earth where water has interacted with other minerals and organic matter. Clay minerals have been detected at several locations on Mars, [15] including Echus Chasma, Mawrth Vallis, the Memnonia quadrangle and the Elysium quadrangle. Spectrography has confirmed their presence on celestial bodies including the dwarf planet Ceres, [16] asteroid 101955 Bennu, [17] and comet Tempel 1, [18] as well as Jupiter's moon Europa. [19] Structure [ edit ] View of tetrahedral sheet structure of a clay mineral. Apical oxygen ions are tinted pink. Wall M (12 March 2013). "Mars Could Once Have Supported Life: What You Need to Know". Space.com . Retrieved 12 March 2013.A. M. Scheidegger, G. M. Lamble and D. L. Sparks, Spectroscopic evidence for the formation of mixed-cation hydroxide phases upon metal sorption on clays and aluminum oxides, J. Colloid Interface Sci., 1997, 186, 118–128 CrossRef CAS PubMed .

M. H. Bradbury and B. Baeyens, Modelling the sorption of Mn(II), Co(II), Ni(II), Zn(II), Cd(II), Eu(III), Am(III), Sn(IV),Th(IV), Np(V) and U(VI) on montmorillonite: Linear free energy relationships and estimates of surface binding constants for some selected heavy metals and actinides, Geochim. Cosmochim. Acta, 2005, 69, 875–892 CrossRef CAS . M. V. Schaefer, C. A. Gorski and M. M. Scherer, Spectroscopic evidence for interfacial Fe(II)–Fe(III) electron transfer in a clay mineral, Environ. Sci. Technol., 2011, 45, 540–545 CrossRef CAS PubMed . R. M. Cornell and U. Schwertmann, The iron oxides : structure, properties, reactions, occurrences, and uses, Wiley-VCH, Weinheim, New York, 2nd, completely rev. and extended edn, 2003 Search PubMed . Chrzanowski, Wojciech; Kim, Sally Yunsun; Abou Neel, Ensanya Ali (2013). "Biomedical Applications of Clay". Australian Journal of Chemistry. 66 (11): 1315. doi: 10.1071/CH13361. S. D. Kelly, B. Hesterdberg and B. Ravel, in Methods of Soil Analysis Part 5—Mineralogical Methods, SSSA Book Ser. 5.5. SSSA, ed. L. R. D. A. L. Ulery, Madison, WI, 2008, pp. 387–463, DOI: 10.2136/sssabookser5.5.c14 .

A. C. Senn, R. Kaegi, S. J. Hug, J. G. Hering, S. Mangold and A. Voegelin, Composition and structure of Fe(III)-precipitates formed by Fe(II) oxidation in water at near-neutral pH: Interdependent effects of phosphate, silicate and Ca, Geochim. Cosmochim. Acta, 2015, 162, 220–246 CrossRef CAS . I know we could have opted for metal coins. There are plenty of sets which are both game specific and open to wider application (the Scythe set is a great example!). But I am not a big fan of the texture, smell, or sound of metal coins. The jingling and tinny clinking jangles my ND brain, and I never carry cash around with me for that reason. But that is personal preference, and I am entitled to emulate monarchic habits whenever I like (haha!). Ironed Out