Sentence:  MICA (<WSD>ISINGLASS</WSD>). Mica is valuable because of its perfect cleavage, transparency, elasticity, non-conductivity of heat and electricity, resistance to decomposition, and non-inflammability. It is mostly used as an insulating material in the manufacture of electrical apparatus. 
Meaning of the word marked with <WSD> tags:  A thin, transparent sheet of mica (probably from its similarity to true isinglass).