Influence des ions étrangers et de la matière organique sur la cristallisation des carbonates de calcium

Scanning electron microscopy and energy dispersive spectrometric microanalysis of crystalline deposits following evaporation of CO3H-, Mg2+ and Ca2+ containing aqueous solutions

“…Our results with the artificial mineral solutions n°3 and n°4 confirm the beneficial influence of magnesium ions on the formation of aragonite noted by Cailleau et al [11], who also showed that some magnesium ions can be incorporated into calcite crystals; the frited edges of the calcite crystals observed in those solutions may be considered as the induced distortion of the original crystal lattice of the pure calcite crystals. As Cailleau et al [11], we have also noticed in the same solutions some images of transformation of vaterite into aragonite, a probable consequence of a dissolution-recrystallization process.…”

“…The rhombohedra are the typical crystallization form of calcite. Ellipsoidal deposits are very similar to the images of vaterite obtained in SEM by Cailleau et al [11] and by Rola [12].…”

“…As Cailleau et al [11], we have also noticed in the same solutions some images of transformation of vaterite into aragonite, a probable consequence of a dissolution-recrystallization process. However, no aragonite could be visualized, either by SEM or by the Feigl technique, in both spa waters TW1 and TW2 deposits, despite the high Mg 2+ concentration and the high Mg/Ca ratio in TW1 spa water.…”

“…The bunches of needles show the same appearance as the vaterite crystals undergoing a secondary transformation into aragonite, as described by Cailleau et al [11]. It may be assumed that the magnesium carbonate deposit which contains some calcium ions is formed of impure magnesite, possibly partly mixed with dolomite.…”

Is the contribution of bacteria to terrestrial carbon budget greatly underestimated?

“…However, biogenic production of vaterite has only been reported for a few groups (Lowenstam and Weiner 1989). It is known that organic matter and medium viscosity can influence CaCO 3 crystallization (Kitano and Hood 1965;Cailleau et al 1979;Addadi et al 1990;Buczynski and Chafetz 1991). This point is particularly important in this study because one of the main cultural characteristics differentiating the two strains studied is the amount of slime produced (mainly exopolysaccharides composed of glucuronic acid, glucose and mannose).…”