Morphology of Calcite (CaCO 3 ) Crystals Growing from Aqueous Solutions in the Presence of Li + Ions. Surface Behavior of the {0001} Form

Calcite crystals were nucleated and grown from supersaturated aqueous solutions in the presence of variable concentrations of lithium. The diagram of supersaturation vs [Li + ]/[Ca 2+ ] concentration ratio (“morphodrome”) shows a continuous habit variation, from the dominant {011̄1} rhombohedron (at low [Li + ]/[Ca 2+ ] ratio) to the dominant {0001} form (at high [Li + ]/[Ca 2+ ] ratio). The morphological change is interpreted in terms of two-dimensional layers having the structure of the monoclinic Li 2 CO 3 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.