  In the generally accepted, but poorly documented model, silicate J-type
C-stars are binary objects for which the silicate emission originates from a
circumbinary or a circumcompanion disc. We aim at testing this hypothesis by a
thorough spectral and spatial observational study of one object:
IRAS18006-3213.
  We obtained, analysed and modeled high spatial resolution interferometric
VLTI/MIDI observations on multiple baselines ranging from 45 m to 100 m. All
observations resolved the object and show the very compact nature of the N-band
emission (~30 mas). In addition, the highest spatial resolution data show a
significant differential phase jump around 8.3 micron. This demonstrates the
asymmetric nature of the N-band emission. Moreover, the single telescope N-band
spectrum shows the signature of highly processed silicate grains. These data
are used to confirm the model on silicate J-type C-stars for IRAS18006-3213. We
show that the most favourable model of the dust geometry is a stable
circumbinary disc around the system, seen under an intermediate inclination.
  The data presented on the silicate J-type C-star IRAS18006-3213 provide
evidence that the oxygen rich dust is trapped in a circumbinary disc. The
formation of this disc is probably linked to the binary nature of the central
star.
