  We explain the linear polarization of the Ca II infrared triplet observed
close to the edge of the solar disk. In particular, we demonstrate that the
physical origin of the enigmatic polarizations of the 866.2 nm and 854.2 nm
lines lies in the existence of atomic polarization in their metastable lower
levels, which produces differential absorption of polarization components
(dichroism). To this end, we have solved the problem of the generation and
transfer of polarized radiation by taking fully into account all the relevant
optical pumping mechanisms in multilevel atomic models. We argue that
`zero-field' dichroism may be of great diagnostic value in astrophysics.
