  IRAS 16279-4757 belongs to a group of post-AGB stars showing both PAH bands
and crystalline silicates. We present mid-infrared images, that resolve the
object for the first time. The morphology is similar to that of the `Red
Rectangle' (HD 44179), the prototype object with PAHs and crystalline
silicates. A two-component model and images suggest a dense oxygen-rich torus,
an inner, low-density carbon-rich region and a carbon-rich bipolar outflow. The
PAH bands are enhanced at the outflow, while the continuum emission is
concentrated towards the center. Our findings support the suggestion that mixed
chemistry and morphology are closely related. We discuss the ISO/SWS spectra of
IRAS 16279-4757. Several bands in the ISO/SWS spectrum show a match with
anorthite: this would be the first detection of this mineral outside the solar
system. Compared to HD 44179, the shapes of PAH bands are closer to those of
planetary nebulae, possibly related to a population of small PAHs present HD
44179, but absent around IRAS 16279-4757. Detailed examination of the spectra
shows the individual character of these two objects. The comparison suggests
that the torus found in IRAS 16279-4757 may have formed more recently than that
in HD 44179.
