Which of the following is good conductor of heat but bad conduct of electricity?

Mica is a good conductor of heat but had a bad conductor of electricity.\nMica has good thermal conductivity due to phonons but doesn’t have sufficient free electrons to be a good conductor of electricity.\nThe important micas are muscovite and phlogopite, which are used in a variety of applications.\nMica’s value is based on several of its unique physical properties. The crystalline structure of mica forms layers that can be split or delaminated into thin sheets usually causing foliation in rocks.