A new crystal growth form of vaterite, CaCO3

Abstract

Microcrystalline vaterite, CaCO3, has been synthesized by decomposition of ikaite, CaCO3.6H20, crystals at room temperature. Scanning electron micrographs show that vaterite occurs as arborescent aggregates -30 to 40 txm in size. This growth form has not been described before. It is of interest that the overall morphology of the vaterite is reminiscent of some dendritic calcite tufas, although on a smaller scale. This similarity opens up the possibility that the calcitic tufas such as that associated with the Quaternary Lake Lahonton, Nevada, may have been deposited as vaterite that changed to calcite, while preserving the original growth form.

The ikaite-to-vaterite transformation: new evidence from diffraction and imaging

“…7(b). Here, dehydrated particles have an arborescent crystal growth form as reported by Shaikh (1990). Individual dehydrated 'ikaite' crystallites ($500 nm) consist of aggregates of smaller regions ($40 nm) of particulates.…”

“…The second process forming vaterite involves decomposition of ikaite (CaCO 3 Á6H 2 O), which crystallizes below $278 K at ambient pressure (Dickens & Brown, 1970). For example, Shaikh (1990) found that dehydration of ikaite warmed to room temperature formed vaterite and calcite, with vaterite predominant and pseudomorphic after ikaite. Vaterite may also be formed by dropping ikaite into boiling water (Brooks et al, 1950;Ito, 1998), by decomposition of ikaite heated between 308 and 342 K (Clarkson et al, 1992;Coleyshaw et al, 2003), and by breakdown of ikaite formed in shells of shrimps frozen for storage (Mikkelsen et al, 1999).…”

Simple solution routes for targeted carbonate phases and intricate carbonate and silicate morphologies

“…On the other hand a spherical/ovoidal substructure was described in the case of smaller (2.0-5.0 μm) diameter globular vaterite precipitated under different conditions [39]; nevertheless the latter substructure deduction was based on surface observations while the globule interior was not probed. An arborescent growth pattern described earlier for vaterite globules (produced by yet another method [40]) and deduced from an examination of the interior of globules is somewhat closer to the case described herein; of course there is no reason for a single possible substructure of vaterite spherulites as a spherical envelope is compatible with various different crystalline (and also semicrystalline, as in the case of polymers) intraspherulitic aggregate morphologies. Overall, it is obvious that dissolved gelatin can strongly affect the type of polymorph of CaCO 3 precipitate.…”

Robust Assembly of Dendrimers as an Active Redox‐Sensing Monolayer: An Example of Oxo‐Anion Sensing

“…CaCO 3 has been studied for more than a century9 with more than 2000 publications during the past 10 years alone. It occurs in nature as anhydrous calcite, aragonite, and vaterite, and in hydrated forms as monohydro‐calcite,10 ikaite,11 and amorphous CaCO 3 12. Vaterite is a short‐term weathering or biomineralization product.…”