The physical and compositional properties of dust: what do we really
  know?
  Many things in current interstellar dust studies are taken as well understood
givens by much of the community. For example, it is widely held that
interstellar dust is made up of only three components, i.e., astronomical
silicates, graphite and polycyclic aromatic hydrocarbons, and that our
understanding of these is now complete and sufficient enough to interpret
astronomical observations of dust in galaxies. To zeroth order this is a
reasonable approximation. However, while these three pillars of dust modelling
have been useful in advancing our understanding over the last few decades, it
is now apparent that they are insufficient to explain the observed evolution of
the dust properties from one region to another. Thus, it is time to abandon the
three pillars approach and to seek more physically-realistic interstellar dust
analogues. The analy- sis of the pre-solar grains extracted from meteorites,
interplanetary dust particles and from the Stardust mission, and the
interpretation of x-ray scattering and absorption observations, supports the
view that our current view of the interstellar dust composition(s) is indeed
too naive. The aim of this review is to point out where our current views are
rather secure and, perhaps more importantly, where they are far from secure and
we must re-think our ideas. To this aim ten as- pects of interstellar dust will
be scrutinised and re-evaluated in terms of their validity within the current
observational, experimental, modelling and theoretical constraints. It is
concluded from this analysis that we really do need to re-assess many of the
fundamental assumptions relating to what we think we really do know about
interstellar dust. In particular, it is clear that unravelling the nature dust
evolution in the interstellar medium is perhaps the key to significantly
advancing our current understanding of interstellar dust. ...
