Diamond is a good thermal conductor. But it is an excellent electrical insulator. How?

Question: Diamond is a good thermal conductor. But it is an excellent electrical insulator. How?
- Keywords:
  conductance,
  conductor,
  diamond,
  electrical,
  energy,
  insulator,
  thermal
Asked by devan to Bob, Katie, Nisha, Sallie, Vee on 3 Jul 2012.
- Bob Bonwick answered on 3 Jul 2012:
  
  Good quesion, one I’ve seen somewhere before! Basically, diamonds are highly organised crystals, and the more organised they are the better they vibrate in harmony at the atomic level. This property alows them to conduct heat really really well, it also means that as it’s so well organised that no current can pass tgrough is due to each atom being fixed in place and not able to send electrons off to creat a current.

Question: Diamond is a good thermal conductor. But it is an excellent electrical insulator. How?