On Mon, 27 Apr 1998, Chan Wei Lik wrote:

Anti-neutronium isn't any different from neutronium and it won't blow up 

in contact with >other stuff.
I'm not too sure about this, I once read a story about using an 
anti-nutronium bomb to turn the Earth into another asteriod belt. 

It's definitely wrong.  Neutral particles such as neutrons also have
anti-particles (which have opposite properties other than charge, obviously),
and the same sort of annihilation takes place that will take place with
charged antiparticles.