The invention provides composites of organic polymeric compositions including a matrix of an organic polymer and a filler distributed throughout the matrix, the flier being present in the matrix substantially as separate particles, each about the fundamental particle size of the filler. The fillers are unique mixed metal hydroxide compositions that are obtainable in sub-micron size particles. These particles are layered and have a BET specific surface area in excess of about 100 m.sup.2 /g. An anion of the particulates is selected to be compatible with the organic polymer thereby providing ease of dispersion of the filler particles throughout the polymer matrix.