Experimental morphology of calcite is analyzed on crystals population grown both in gel and in aqueous
solution. A comparison is made between growth in pure solution and in the presence of specific
impurities (such as lithium and acetate ions) giving rise to different habit modifications. The appearance
of important {0001} and {0118} calcite forms is explained either in terms of 2D epitaxial layers or by
random adsorption. Finally, the production of crystalline bubbles of calcite growing in solution around
gas cavities is explained as a typical case of heterogeneous nucleation and growth favored at the
complex interface solution/gas/crystal. All this complex phenomenology along with its interpretation
can be thought as a first physico-chemical and crystallographic step in ruling practical drawbacks such
as the crystal caking and the scale problems.