I understand it was dust picked up by an unusual cold front in the desert north of Adelaide & in western NSW. The only conspiracy might have something to do with global warming! The last big dust storm I believe was back in 2001 or 2002 (I may have the year wrong?!)...
Dust storm once again in Newcastle but as Sydney is now in the clear it wont last much longer now. Amazing, 2 major dust storms inside of a week. How unusual is that?