A mounting mat for an exhaust gas treatment device including inorganic fibers, organic binder, antioxidant, optionally clay and optionally intumescent material. The exhaust gas treatment device includes a housing, a fragile catalyst support structure resiliently mounted within the housing, and the mounting mat disposed in a gap between the housing and the fragile catalyst support structure. Additionally disclosed are methods of making a mounting mat for an exhaust gas treatment device and for making an exhaust gas treatment device incorporating the mounting mat.