AbstractUpgrading mica by increasing aspect ratio and coupling efficiency and combining mica with fibers has led to new uses as a reinforcement for thermoplastics and thermosets. The greatest growth in mica use has been in the thermoplastics, such as polypropylene and thermoplastic polyesters. Effects to be expected from using mica as a reinforcement include improved tensile and flexural strength, much‐increased dimensional stability and heat resistance, enhanced stiffness and electrical resistivity, and reduced permeability to gasses and liquids. Major parameters that influence the composite properties include the mica flake size, orientation, aspect ratio and volume fraction, coupling efficiency, and crystallinity of the polymer matrix. Mica composites are molded from direct blends or are precompounded in the manner used for fillers. Mica‐reinforced polypropylene (PP) is cost‐effective in replacing glass‐fiber‐reinforced PP and may even substitute for glass‐reinforced Nylon 66 in some applications. Markets for fillers for plastics are expected to grow faster than for the base polymers due to low cost, availability, and low energy utilization. Mica is expected to be one of the fillers with the highest market growth rate.