Abstract: Photon-diffusive coating compositions contain a binder and a mineral containing at least about 65%, preferably at least about 75%, and most preferably at least about 85% to 90% silica, of which at least about 60%, preferably at least about 75% to 85% is in the crystal form of cristobalite, which has been reacted with sodium hydroxide. In typical embodiments, ground Klannerite.RTM. is reacted with sodium hydroxide in an aqueous slurry by the application of heat to just below the boiling point until the pH falls to below 12, and then a latex binder is added. Preferred binders comprise a mixture of polysaccharide resin and a latex binder; the polysaccharide resin is added, the mixture is neutralized somewhat, and then the latex binder is added. The viscosity of the final composition may be adjusted by adding water. Cured coatings exhibit good spectral reflectance and are useful in a variety of applications such as coating furnace interiors.