The difference in
hardness between diamond and graphite is that diamond has an ordered
arrangement of atoms within its structure that makes it harder and stronger
than graphite. This is due to the high pressure and high temperature that it
went.
This is called adaptation. An example would be a polar bear with white fur. They have this to be more efficent hunters, as they use it as a type of camouflage in order to sneak up on prey. Brown bear use this in the same way but their environment requires them to be brown in order to blend in beter with trees. So basicly adaptation