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

Fernández Díaz, Lourdes 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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Abstract

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 bounded 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:08 Feb 2012 13:27

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