Morphology of Calcite (CaCO₃) Crystals Growing from Aqueous Solutions in the Presence of Li⁺ Ions. Surface Behavior of the {0001} Form

Abstract

Calcite crystals were nucleated and grown from supersaturated aqueous solutions in the presence of variable concentrations of lithium. The diagram of supersaturation vs [Li+]/[Ca2+] concentration ratio (“morphodrome”) shows a continuous habit variation, from the dominant {011̄1} rhombohedron (at low [Li+]/[Ca2+] ratio) to the dominant {0001} form (at high [Li+]/[Ca2+] ratio). The morphological change is interpreted in terms of two-dimensional layers having the structure of the monoclinic Li2CO3 crystal which are epitaxially adsorbed on the restructured {0001} form of calcite. Hence, even if {0001} is a K form (in the sense of Hartman-Perdok), the corresponding surface behaves like a F form, growing layer by layer from low to high supersaturation values.