Abestos is a mineral fibre that is prevalent in about 70% of the earths crust and has beeen in use since the roman empire.
The form of asbestos depends upon the matrix it is contained in in its raw state it is a fibre, aminute one thus the reason it is so dangerous as the human airway cannot filter it.
Its ok to break it up as long as you dont cut it, just use a hammer and avoid the main of the dust, as has been said its the blue stuff thats dangerous.
I personally think that fibre glass (loft insulation) is a lot worse than asbestos