  We demonstrate natural optical activity in disordered ensembles of non-chiral
plasmonic resonators. We show that the statistical distributions of rotatory
power and spatial dichroism are strongly dependent on the scattering mean free
path in diffusive random media. This result is explained in terms of the
intrinsic geometric chirality of disordered media, as they lack mirror
symmetry. We argue that chirality and natural optical activity of disordered
systems can be quantified by the standard deviation of both rotatory power and
spatial dichroism. Our results are based on microscopic electromagnetic wave
transport theory coupled to vectorial Green's matrix method for pointlike
scatterers, and are independently confirmed by full-wave simulations.
