This invention pertains to a laminate structure suitable for use as electrical insulation, comprising a first paper layer comprising 90 to 99 weight percent uniformly distributed calcined mica and 1 to 10 weight percent supporting material, a majority by weight of the supporting material being in the form of a floc; and a support layer comprising unidirectional filaments or unidirectional yarns or woven yarns; wherein the support layer is bound to the first paper layer; the laminate structure having a dielectric strength of 15 kV/mm or greater, a Gurley porosity of 400 seconds or less, and total mica content of 60 weight percent or greater. The laminate structure can further comprise a second paper layer bound to the support layer, the second paper layer comprising 90 to 99 weight percent uniformly distributed calcined mica and 1 to 10 weight percent supporting material, a majority by weight of the supporting material being in the form of a floc.