  When considering grinding of minerals, scaling effect induces competition
between plastic deformation and fracture in brittle solids. The competition can
be sketched by a critical size of the material, which characterizes the
ductile-brittle transition. A first approach using Vickers indentation gives a
good approximation of the critical size through an extrapolation from the
macroscopic to the microscopic scales. Nanoindentation tests confirm this
experimental value. According to the grain size compared to the indent size, it
can reasonably be said that the mode of damage is deformation-induced
intragranular microfracture. This technique also enables to perform cyclic
indentations to examine calcite fatigue resistance. Repeated loadings with a
nanoindenter on CaCO3 polycrystalline samples produce cumulative mechanical
damage. It is also shown that the transition between ductile and brittle
behaviour depends on the number of indentation cycles. The ductile domain can
be reduced when the material is exposed to a fatigue process.
