  Zero-field muon-spin relaxation measurements of the frustrated triangular
quantum magnet AgNiO2 are consistent with a model of charge disproportionation
that has been advanced to explain the structural and magnetic properties of
this compound. Below an ordering temperature of T_N=19.9(2) K we observe six
distinct muon precession frequencies, due to the magnetic order, which can be
accounted for with a model describing the probable muon sites. The precession
frequencies show an unusual temperature evolution which is suggestive of the
separate evolution of two opposing magnetic sublattices.
