Inorganic since bricks are burned at high temperature and all organic
material is incinerated.
Affections by Cladosporium is possible when the bricks are exposed to
constant damp or there is damp in its pores and if nutrients are available
in sufficient quantities. These affections are the most severe you can
get and are very hard to get rid of.
When the black mould has gotten a hold, it establishes itself fast.
All black mould, its spores and the surface must be sterilized and disinfected
for the affections to stop. Future affections become impossible for
the next four years.