A combustible heat source for a smoking article is provided, including carbon and a binding agent. The binding agent includes a combination of three binder components: an organic polymeric binder material, a carboxylate burn salt, and at least one non-combustible inorganic binder material. The at least one non-combustible inorganic binder material includes a sheet silicate material. Preferably, the combustible heat source further includes an ignition aid.