  Using {\it ab initio} band structure calculations we show that mineral
cubanite, CuFe$_2$S$_3$, demonstrates an orbital-selective behavior with some
of the electrons occupying molecular orbitals of $x^2-y^2$ symmetry and others
localized at atomic orbitals. This is a rare situation for $3d$ transition
metal compounds explains experimentally observed absence of charge
disproportionation, anomalous M\"ossbauer data, and ferromagnetic ordering in
between nearest neighbor Fe ions.
