The invention relates to a composition comprising mica and glass, said glass comprising: 10 to 30 mol % of SiO2 5 to 40 mol % of BaO 15 to 30 mol % of B2O3, the sum of the concentrations of zinc oxide, alkali metal oxide and alkaline earth oxide in the glass extending from 15 to 65 mol %. This composition is intended to be molded at a temperature above the Tg of the glass so as to form composite parts that can serve as an electrical insulator.