  We continue our work on a proposal for what dark matter could be, namely that
the dark matter consists of essentially macroscopic objects built from ordinary
matter. The only element of new physics is that there should exist several
types or phases of vacuum. Then the dark matter particles are bubbles of a new
type of vacuum filled with ordinary matter - say diamond - under high pressure
and the whole bubble is supposedly contaminated by the materials in the extra
galactic or intragalactic space able to form dust. The dust has a lower than
dimension 3 structure and may well be long chains of atoms. We begin
speculations on identifying the phase transition between the vacua, which we
require in our model, with a (second order?) transition revealed in the
Columbia plot with quark masses as axes. In the corner of small quark masses
there is a true phase transition as temperature is raised, while outside this
region there is instead no genuine phase transition under variation of the
temperature but rather only a crossover.
