  We analyze the temperature dependence of conductivity in thick granular
ferromagnetic compounds NiSiO2 and in thin weakly coupled films of Fe, Ni and
Py in vicinity of metal-insulator transition. Development of resistivity
minimum followed by a logarithmic variation of conductivity at lower
temperatures is attributed to granular structure of compounds and thin films
fabricated by conventional deposition techniques. Resistivity minimum is
identified as a transition between temperature dependent intra-granular
metallic conductance and thermally activated inter-granular tunneling.
