  We construct a model for the quark mass and flavor mixing matrices, based on
the hypothesis that the flavor weak eigenstates in the three families are
distinguished by a spontaneously broken discrete $Z_6$ chiral symmetry. In a
leading partially symmetric approximation, the model accommodates the family
mass spectra, with a CKM matrix that is exactly unity. Adding small asymmetries
in first order perturbation theory gives a CKM matrix with the correct
qualitative structure, with $s_{23}/s_{12}$ and $s_{13}/s_{12}$ naturally of
order $M_s/M_b$.
