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

Katy Mee answered on 17 Jun 2010:

I’ll let the physicists/chemists answer this one properly……but as far as i know diamonds are the hardest minerals in the world (10 on Moh’s scale of hardness) which is why they’re often used on the end of drills for boring through rock. Their hardness is something to do with the strong covalent bonding (where electrons are shared between atoms) and this is why is it such a strong conductor….i have no idea why it is an excellent eectrical insulator so i’m hoping one of the others will be able to fill you in with that!