Sheet material containing exfoliated vermiculite

A sheet material adapted for use as heat resistant gaskets, heat insulation, electrical insulation, and supporting media for dehumidifiers and heat exchangers, said material being in the form of a fibrous web comprising organic fiber, organic binder, and a blend of completely exfoliated vermiculite free from asphalt with another inorganic asbestos-free particulate filler, said blend having a particle size to pass a No. 80 screen, the amount of said fiber being from 1 to 30% by weight and the amount of said blend being from 70 to 99% by weight, the amount of binder being from 3 to 30% by weight, all based on the total weight of fiber and blend, and the amount of vermiculite being from 25 to 70% by weight of said blend, said sheet material having a density of 0.64 to 1.92 g per cc, a tensile strength of at least 500 psi, a compression of 7 to 50% and a recovery of 20 to 70% at 1000 psi, a sealability of 30 cc/hr maximum at 500 psi, and a stress relaxation of 50% maximum at 212.degree. F.