The morphology of calcite crystals grown in a porous medium doped with divalent cations



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Fernández Díaz, Lurdes and Astilleros García-Monge, José Manuel and Pina Martínez, Carlos Manuel (2006) The morphology of calcite crystals grown in a porous medium doped with divalent cations. Chemical geology, 225 . pp. 314-321. ISSN 0009-2541

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Calcite crystals were grown in the presence of small concentrations (50, 200, and 600 ppm) of divalent cations (Ba2+, Sr2+, Co2+ and Mn2+) in a silica hydrogel medium. The calcite crystals grown in the presence of cations larger than Ca2+ (Ba2+ or Sr2+) developed rhombohedral habits defined by {101¯4} form, similar to the morphology of calcite grown in a pure gel. SEM images show that growth on {101¯4} occurs by lateral advancement of layers founded by macroscopic dendritic or jagged steps. In the case of calcite crystals grown in a gel doped with cations smaller than Ca2+ (Co2+ or Mn2+), a variety of morphologies was obtained, ranging from blocky crystals (at lower concentrations: 50 and 200 ppm) to peanut-like aggregates, spheres and spherulites (at 600 ppm). The macroscopic morphological characteristics of such doped calcite crystals reflect closely the growth behaviour of calcite {101¯4} surface at a nanoscale, reported by previous AFM studies. Morphological features have been interpreted on the basis of the modification of growing steps characteristics as a consequence of asymmetrical cation incorporation. The use of such morphologies as a criterion of biological activity is, therefore, unreliable.

Item Type:Article
Uncontrolled Keywords:Calcite; Crystal morphology; Gel crystal growth method; Impurities
Subjects:Sciences > Geology > Crystallography
ID Code:14545
Deposited On:08 Feb 2012 13:27
Last Modified:07 Apr 2021 10:00

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