Reversed Crystal Growth of Calcite in Naturally Occurring Travertine Crust

Abstract

Abstract:A microstructural investigation by electron microscopy on a travertine specimen collected from Munigou National Park, Sichuan Province, China revealed evidence of a non-classical reversed crystal growth route previously only discovered in synthetic materials. Examination of the travertine specimen suggests that the presence of organic matter initiates the oriented aggregation of calcite nanocrystallites. Surface re-crystallisation of the aggregates leads to a single crystalline rhombohedral shell with a polycrystalline core. This core-shell structure carries a strong resemblance to synthetic calcite prepared in the presence of chitosan, where the growth of calcite was found to follow the so-called reversed crystal growth process. It is proposed that the similar roles of biomolecules in naturally occurring travertine and chitosan in the synthetic system are based on their isoelectric points and the polymerizable property of long chain chemical structures. This study is important so that the structural similarities between naturally occurring biominerals and biomimetic materials can be further understood.

Origin of a global carbonate layer deposited in the aftermath of the Cretaceous-Paleogene boundary impact

“…4, 6). These textures resemble those described in travertine (Greer et al, 2017;Jones, 2017b), in which polycrystalline cores were succeeded by single-crystal faces. Greer et al (2017) invoke a mechanism by which the assembly of mesocrystals is mediated by biomolecules, as reproduced in experiments involving chitosan.…”

“…These textures resemble those described in travertine (Greer et al, 2017;Jones, 2017b), in which polycrystalline cores were succeeded by single-crystal faces. Greer et al (2017) invoke a mechanism by which the assembly of mesocrystals is mediated by biomolecules, as reproduced in experiments involving chitosan. Diagnostic specimens resembling cyanobacteria are found throughout the micriterich layer, notably with the lowermost sample 3 cm above the boundary at Site 1262.…”

Study on Carbonation of Porcine Blood Hydrogel in the Composite Mortar of Ancient Chinese Architectural Painting

“…These morphological features were similar to that of calcite reported in the literature [43][44][45][46]. It has been found that the morphology of CaCO3 precipitates formed in hydrogels is dependent on the diffusion reaction [47]. In the porcine blood hydrogel, due to the uneven distribution of lime water and the difference in the diffusion of both Ca 2+ ions and CO2, these formed calcite crystals with different morphologies that could be understood.…”

Physiology, Metabolism, and Fossilization of Hot-Spring Filamentous Microbial Mats

“…In addition, EPS can influence bacterial adhesion onto solid surfaces or improve the cohesion of sedimentary particles as during stromatolite ( microbialite ) formation (Tourney and Ngwenya, 2009, 2014). Modern travertine deposition in other hot springs has also observed that travertine preferentially nucleates on EPS, beginning with 5–80 nm diameter globules of amorphous calcium carbonates that coalesce and transform into well-developed acicular aragonite crystals (Greer et al, 2017).…”