The invention relates to a composition including mica and glass, said glass including: 10 to 30 % of SiO2 moles,5 to 40 % of BaO moles,15 to 30 % of B2O3 moles, the total level of zinc oxide, alkaline oxide and alkaline-earth oxide moles in the glass ranging from 15 to 65%. Said composition is intended for being moulded at a temperature higher than the Tg of the glass to form composite parts that can be used as electrical insulators.